technical exam flashcards

Question 1

What are the different mental models of sustainability?

Answer 1

• Efficiency
  
  • Inter shift shut down focus: no production no energy use
  • Cement can be 20% more efficient with same costs
  • 10,000 litres vs 60 for a pair of jeans
• Value
  
  • Fast fashion: use a small interchangeable wardrobe
  • Fire hose handbag
• Technology
• System
  
  • AB sugar
  • Mallorca

Question 2

What is eco efficiency?

Answer 2

Simply do more with less

Question 3

Factories making the same product can show large variation in operational efficiencies.

Outline the factors which may influence variations in resource efficiency.

Suggest ways in which resource efficiencies may be improved. Use specific examples, from module presentations or from your own experience, to illustrate your answer.

Answer 3

Improvement hierarchy:

• Prevention
  
  • eliminate unnecessary equipment/processes
  • switch off equipment when not in use
  • e.g. use gravity feeds, standby mode
• Waste reduction
  
  • good maintenance and repair
  • sort/treat waste to optimise its value
  • optimise layout
  • e.g. fix leaks, insulate, separate waste, keep equipment clean
• Resource use reduction
  
  • optimise production schedule and start up
  • match supply and demand
  • e.g. lower compressed air pressure, use highest temp for cold storage
• Reuse of waste as a resource
  
  • look for compatible waste demand
  • understand reuse opportunities
  • e.g. reuse cutting fluid, recover waste heat and water
• Substitution
  
  • replace resource (renewable and non toxic)
  • change way function is achieved
  • e.g. replace cutting tools, install optimum motors, replace obsolete tech

Question 4

What is the circular economy?

Answer 4

Question 5

Describe the waste and energy hierarchy and how these feed into the improvement hierarchy

Answer 5

Waste hierarchy:

• Avoid
• Reduce
• Reuse/recycle
• Treatment
• Energy recover
• Landfill

Energy hierarchy:

• Minimise demand
• Energy efficiency
• Renewable source
• Low carbon technology
• Carbon offsetting
• Conventional energy

Improvement:

• Prevent
• Reduce waste
• Reduce resource use
• Reuse waste as a resource
• Substitute, upgrade, replace

Question 6

What is sustainable development? Define the methodology.

Answer 6

Development that meets the needs of the present without compromising the ability of future generations to meet their needs.

1a. Define objectives, size, time and geographical scale
1b. Identify key design issues and appropriate metrics
* Metrics: e.g. energy generation per unit mass
2. Identify stakeholders and their concerns/power
3. Fact finding: material efficient design, resource efficient design
4. Synthesis: assess data and analyse against three Ps (planet, profit, people)
5. Reflection: is this sustainable

Question 7

What is an LCA. What are the issues associated?

Answer 7

LCA: life cycle analysis

Issues

• It is time consuming, expensive and subjective.
• Too late in the design process. Detail only in retrospect.
• Need a simple approach. Choose a single metric e.g. carbon dioxide generated or energy.

Question 8

How is a CES eco audit carried out?

Answer 8

Choose the life phase which dominates:

• materials, manufacture, transport, use or disposal

Question 9

Explain the concept of value uncaptured?

Answer 9

Value captured: the benefits delivered to stakeholders either or not related to monetary profit, e.g. improved energy efficiency

Value uncaptured:

• Value missed: value inadequately captured or lost,
  
  • e.g. not using specialist knowledge, inefficient use of data
• Value destroyed: negative outcomes of business,
  
  • e.g. pollution, bad working conditions
• Value surplus: redundant value that is larger than requirements
  
  • e.g. over capacity of labour, excess functionality
• Value absent: value which is required but has not been created
  
  • e.g. lack of skills, lack of warehouse space, unmet customer needs

Value opportunity: the new opportunities of additional value creation through new activities and relationships, e.g. the opportunity to utilise identified waste

Stakeholders must be considered:

• Investors, environment, society, employees, suppliers, customers

The concept of value uncaptured is used to understand failed value exchanges among multiple stakeholders across a business network to uncover new value opportunities.

Question 10

Explain the different waste streams that are utilised and sold in AB sugar

Answer 10

• Molasses and Bagasse made into:
  
  • Alcohol
  • Biofuel
  • Furfural: fungicide/weed killer
  • Betaine: used for young salmons
• Pulp and lime made into:
  
  • Salts
  • Raffinate and Vinasse: animal feed
• Water, effluent and soil made into:
  
  • Algae and topsoil
• CHP, heat and CO2 made into:
  
  • Power generation
  • Tomatoes/marijuana
  • Biogas

Question 11

Explain riversimple’s 7 point strategy

Answer 11

1. Network electric car
2. Sale of service not cars
3. Sale of service upstream
4. City by city strategy
5. Distributed manufacturing
6. Open source designs
7. Shared ownership

Question 12

Could we use a single polymer for cheese production?

Answer 12

Carbon footprint is minimised by using multi-layer film

Best single polymer is PVDC – but it’s difficult to recycle and expensive

Best easily recyclable polymer is PET.

Question 13

What happens to polymers at end of life?

Answer 13

Disposal:

• Mechanical recycling
  
  • Sort, shred, clean, melt/reprocess (extrusion, pressing)
  • Primary Recycling (closed-loop):
    
    • Standard practice in factories e.g. Out-of-spec low-density polythene (LDPE) injection mouldings are pelletised and immediately returned to injection moulder input
  • Secondary Recycling (post-consumer):
    • Involves downcycling e.g. fleeces and other clothing from PET bottles, (Patagonia) household waste bags from LDPE
  • Sorting is important. Commonly used automated methods:
    
    • near-infra-red spectroscopy; optical recognition; electrostatics; X-ray fluorescence; density methods including flotation; melting point
• Composting
• Feedstock/chemical recycling
  
  • Polymers broken down into constituent monomers which can be used in refineries or in petrochemical production
  • Plants are very large and costly; processing energy is high
  • Useful for specialist applications (e.g. process for recycling tetrapaks)
• Other (grinding for filler)
• Energy recovery
• Landfill

Question 14

What are the main elements in a business model?

Answer 14

Value proposiiton

Value creation

Value capture

Question 15

Should you use paper and cardboard or a polymer for packaging?

Answer 15

Paper & card have greater impact than plastic.

Environmental footprint of paper/card is high:

Manufacturing operations very energy-intensive (turning trees into chips, processing; needs 60% more energy than plastics) and generate much more toxic waste than plastics (water pollutants 50x higher; air pollutants 70% higher).

End-of-life: plastics recycling requires only 10% energy of paper/card recycling.

Conclusion: All single-use disposable packaging is environmentally undesirable.

Expectation: Transition to re-usable plastic crates, charging a deposit.

Question 16

Give examples of sustainable business models

Answer 16

Formula E

Dutjahn Sandalwood Oils

Elvis & Kresse

Question 17

Explain the steps of the value mapping process

Answer 17

Steps 1, 2 and 3 – Setting the scene

• Decide the unit of analysis (product/service, business unit, company or an industry)
• Add or modify any missing stakeholders
• Identify the purpose of the unit of analysis

Steps 4, 5 and 6 –

• Map the value (follow the spiral, clockwise) current value captured for each stakeholder
• Value uncaptured, i.e. value missed / destroyed / surplus / absence for each stakeholder
• Stakeholder tensions may arise

Step 7 – Generate value opportunities for sustainability

• Eliminate value destroyed and absence - reducing the value uncaptured, turning it into positive value
• Utilise value missed and surplus – reusing the value uncaptured, increasing value in the business network
• Look for value opportunities – extending the value captured, shifting to higher value added

Question 18

Define microplastics and their issues for marine life

Answer 18

Defined as any piece of plastic less than 5mm in length, but often less than 0.5mm (small enough to evade standard filtration systems)

Origins include:

synthetic fibres (from washing clothing); microbeads from cosmetics and personal care products; partially broken-down waste plastics

Issues:

Larger bits:

• Suffocation, entanglement.
• Sharp edges particularly when ingested

Smaller fragments (sub-millimeter):

• Mistaken for food so can cause starvation
• Unexpected effect: mimic oestrogen, disrupts reproductive ability in fish and causes infertility

Additives from processing and product requirements are released from polymer waste (and during a product’s useful life…)

Additives leach out and contaminate fluids: can mimic oestrogen and disrupt reproductive ability in animals and fish so impacting food supplies. But can also cause hormone-related problems in consumers (including humans)

Question 19

What are the functions of primary packaging?

Answer 19

• Mechanical protection:
  
  • damage reduction (impact, surface damage from handling)
• Acts as barrier layer:
  
  • keeps oxygen out (vacuum packs); keeps protective atmospheres in (typically nitrogen or carbon dioxide); prevents water loss
• Increases product shelf life:
  • reduces food wastage can reduce amount of processing and additives increases acceptable length of supply chain (global food production)
• Hygiene; environmental barrier, keeps smells in
• Tamper evidence:
  
  • Provides assurance that the product is intact and is as produced by the manufacturer (right product, right quality, right quantity)
• Information, advertising and legislation

Question 20

What is the production footprint like compared to packaging footprint?

Answer 20

Packaging footprint tiny compared with food production footprint. Recycling saves a little energy, but there are other reasons for recycling

Question 21

Why are polymers so difficult to recycle?

Answer 21

• Quality of input material is critically important to value of output
• Polymers cannot be refined or purified: everything that goes into the mechanical recycling process is incorporated into the output recycled material
• Difficult to analyse polymers to know exactly what is in them

Ideal input:

• single polymer:
  
  • polymers cannot be defined by simple chemical formula: properties depend on chain length, chain configuration (branched or linear chain, position of side groups)
• clean
  
  • Not mixed with other materials (e.g. metal, paper).
  • Not contaminated by food, or by anything else (e.g. bottle used for bleach)
    • Polymers contain small amounts of many different additives to improve processing to stabilise against environment in service: includes UV, fire resistance
• uncoloured

Question 22

How can polymer recycling be increased?

Answer 22

• Government subsidies
  
  • Legislation forcing increased recycling – e.g. required minimum recycled content in products
  • Oil prices rise, so re-processed polymer becomes more valuable
• Design for recyclability:
  • Narrower range of polymers
  • Think about joining methods
  • Use sub-optimised material (but increases weight of article, uses more material)
  • No coloured plastics
• Advances in recycling technology to produce higher-grade higher-value material
  
  • Improved sorting
  • Better tolerance of impurities in mechanically recycled plastics
    e. g. Using calcium carbonate to react with chlorine from PVC
  • Processing of mixed plastics
    e. g. Research into compatibilising mixed polymers
  • More chemical recycling

Question 23

What should we do about plastic packaging?

Answer 23

Knee-jerk reactions:

• Get rid of plastic packaging
• Ban all single-use plastic

Superficially plausible but problematic:

• Use bio-based, biodegradable polymers

More considered reactions:

• Stop using un-necessary plastics (and packaging)
  
  • Packaging directive: eliminate all ‘avoidable plastics waste’ by 2042
• More packaging re-use
  
  • Returnable bottles, re-fillable containers
  • Barriers: logistics, infrastructures
    
    • standardised designs: needs support from marketing people
    • safety, hygiene, product assurance and quality control
    • consumer preferences
• Materials choices: all packaging should be recyclable
• Increase recycling: build UK recycling capacity
• Stop uncontrolled exports
• More energy from waste but only as a temporary measure

Correctly used and disposed, plastic reduces food waste; carbon footprint of packaging is tiny compared with food production

Question 24

Define what an LCA might aim to achieve.

Answer 24

LCA is aimed at providing a measure of the total environmental impact of the kettle, from material production, manufacture, use and disposal. It is particularly useful for comparing the impacts of products, as much like-for-like as possible. For a kettle, one might compare different materials or production technologies.

Question 25

Compare

LCA with Eco Audit for a kettle

Answer 25

LCA (life cycle analysis) provides outputs under headings of

• resource consumption (including materials, energy, water),
• emissions (including various gases, particulates),
• and impact assessment (including ozone depletion, global warming, acidification, human toxicity).

These different factors cannot readily be combined, so are usually left as separate datapoints.

There is currently no single method for conducting an LCA, but ISO14040 is an international standard which sets out a framework.

• It is a systematic way of analysing the impact of an activity or producing a product.
• It considers all phases of the lifecycle.
• It is useful for comparing the impacts of comparable activities (e.g. two ways of making a product).

LCA is expensive, time-consuming, does have subjective elements, and is retrospective (normally too late to influence design).

For the kettle, the outputs will include all those noted above (maybe in subcategories as well). It may be noted that most of the impact comes from the use phase.

Eco-audit provides a single measure of impact, which may be energy or CO2.

This is generated under the headings of

• Material, Manufacture, Transport, Use and Disposal and usually presented as a bar chart.

In addition a summary is generated showing detailed breakdown, life phase energies, life carbon footprints.

• Eco-audit provides a quick and approximate measure of one aspect of environmental impact.
• Does not take full account of other eco factors which are included in full LCA.

The following factors may be noted:

• gaseous emissions (e.g. SOX, NOX), particulates, ozone depletion potential, acidification potential, human toxicity potential.
• Water use is another big factor which may increasingly become a show-stopper.

It identifies the dominant life phase so allowing a targeted approach to reducing environmental impact. It is done early enough in the design process to influence design.

For the kettle, the use phase dominates, so the biggest improvement may be made by improving thermal insulation of the kettle.

Question 26

Outline the outputs that will be generated from an LCA analysis. What are the difficulties with using these outputs?

Answer 26

Outputs can be generated under nine environmental themes (students were not expected to remember details for these, but they are stated here for completeness):

• Abiotic depletion potential;
• Energy depletion potential;
• Global warming potential;
• Ozone depletion potential;
• aquatic/terrestrial ecotoxicity;
• acidification potential;
• human toxicity;
• photochemical oxidant creation;
• nitrification potential.

All have different metrics, so combining them is not straightforward. Most studies choose only some of the headings, and tend to keep the figures separate under them. Assessment of impact therefore requires some judgment, such as which metrics are most important.

The choice of system boundaries is crucially important in any LCA. There is some flexibility about how this is done, so it is important that similar system boundary choices have been made when making comparisons between different LCAs. Similar care should be taken over allocation and choice of functional unit.

Question 27

Discuss the impacts on the lifecycle (positive and negative) of including a barrier function in packaging.

Answer 27

Environmental impacts:

• Product life increased by orders of magnitude, so (simplistically) reduces wastage.
• But the lengthening of the supply chain promotes globalisation of food production, with both positive and negative environmental consequences (factors include transport, agricultural policies and impacts).
• The complexity of packaging material may in some cases be increased if a barrier function is included (e.g. as an additional polymer layer in cheese packaging, or with metallised films), reducing recyclability.
• Considering packaged food as a whole, the environmental impact of the food production hugely dominates the total impact.
• So the impact of the packaging itself is normally considerably less than 5% of the total impact, and any end-of-life considerations are (in terms of energy or carbon footprint) negligible.

Question 28

What is a system boundary? Discuss what factors should be considered when defining a system boundary for environmental analysis of plastic film packaging for cheese produced and consumed in the UK.

Answer 28

• A system boundary is used to define what should be included for a particular environmental analysis. For this case, the following factors should be considered:

Packaging:

• Material production, manufacturing process, transport between different stages. End-of-life disposal.

Supply chain issues:

• The weight and volume of the packaging and how it affects the density with which the product can be packed for transport.

The analysis is of the packaging, so the production of the product being packaged (cheese) is outside the boundary. Nevertheless, the effectiveness of the packaging has implications for the shelf-life (lifetime) of the product.

Question 29

Briefly describe how an eco-audit of a plastic film packaging for cheese would be carried out.

What are the outputs of such an analysis?

What assumptions might you expect to make in carrying out the assessment?

How would you use the analysis to propose reduction in the environmental impact of the packaging?

Identify any additional factors relevant to environmental impact assessment which should be considered that are not included in this analysis.

Answer 29

User inputs include

• Bill of materials,
• shaping processes,
• transport needs,
• duty cycle.

The Eco database is used to generate

• embodied energies,
• process energies,
• CO2 footprints,
• unit transport energies etc.

The eco-audit can be facilitated using CES. Assumptions may typically include details of the materials used.

Outputs include a bar-chart showing impact of the four lifecycle phases: material, manufacture, transport and use, plus end-of-life.
The analysis should be used to identify the phase with the greatest impact, and to focus on this for action.

Additional factors:

• In assessing the wider environmental consequences of food packaging, the domination of the food production aspect should be remembered.
• Not specifically mentioned are the factors associated with the function of food packaging in reducing food wastage, including the barrier function described under (a) (ii).

Question 30

Briefly outline how LCA and Eco-Audit should be carried out. What information is required?

Answer 30

LCA:

• Define goal and scope of study.
• Define
  
  • the functions of the product system,
  • functional unit,
  • boundaries and
  • product system.
• Define methodology, assumptions and limitations.
• Perform inventory analysis.
• Assign environmental impacts of product system.
• Interpret results.

Eco-audit:

User inputs include

• Bill of materials,
• shaping processes,
• transport needs,
• duty cycle.

The Eco database is used to generate embodied energies, process energies, CO2 footprints, unit transport energies etc.

Question 31

With reference to the use of LCA for the production of biodiesel, outline the meaning and significance of the terms system boundary and allocation.

Answer 31

The system boundary defines what is included in the LCA. Although the protocol is documented, it is subject to interpretation. For biodiesel, there will be variation in the extent to which growing of the crops is included, and how the agricultural systems are treated.

Allocation: Any process involves many systems, which are not independent. Allocation is the appropriate distribution of responsibility for resource consumption, emissions and wastes from processes.

Question 32

Explain how you would use an Eco-Audit to make recommendations on how to reduce the environmental impact of a refrigerator. Give a prioritised list of proposals to achieve this, justifying your answer. What assumptions are made in performing the analysis?

Answer 32

• The eco-audit will generate a bar chart in which the dominant phase is the duty cycle, followed by the material.
• Increasing the operating efficiency of the fridge to reduce energy consumption will be the main recommendation.
• This will be achieved primarily by improving thermal insulation, though note that this will also increase the impact of the Materials phase.
• There may be scope within the design of the fridge for reducing the heat transfer when the fridge door is open – e.g. compartments in the fridge to retain the cold.
• Optimising the efficiency of the cooling mechanism is something else to be done – but there may not be much improvement possible there.
• There may be scope for encouraging good behaviour by incorporating alarms that sound if the fridge door is left open.

Question 33

What is the difference between risk and uncertainty?

Answer 33

Risk

Present when managers know the possible outcomes of a particular course of action and can assign probabilities to them

Uncertainty

The future is unknown, and probabilities cannot be given for outcomes

Question 34

What is the expected utility theory?

Answer 34

• Actual decisions made depend on the willingness to accept risk
• Expected utility theory allows for different attitudes towards risk-taking in decision making
  
  • Managers are assumed to derive utility from earning profits
• Managers make risky decisions in a way that maximises expected utility of the profit outcomes
• Utility function measures utility associated with a particular level of profit
  • Index to measure level of utility received for a given amount of earned profit
• Managers attitude toward risk
  
  • Determined by the manager’s marginal utility of profit
  • Marginal utility (slope of utility curve) determines attitude towards risk

Question 35

How can you tell if someone is risk averse from the utility curve?

Answer 35

You are risk averse with respect to a gamble if you prefer the expected value of the gamble with certainty to the gamble itself.

You are risk averse if the expected value is greater than the certainty equivalent.

Question 36

Explain the flaws in the utility model by comparing it with the prospect model

Answer 36

Question 38

Explain the components of a simple queuing system. Give examples

Answer 38

The calling population

• The population which customers/jobs originate
• The size can be finite or infinite (the latter is most common)
• Can be homogeneous (only one type of customer/job) or heterogeneous

The arrival process

• Determines how, when and where customer/jobs arrive to system
• The important characteristic is the customers/jobs inter arrival times
• Correct specification of the arrival process requires data collection of interarrival times and statistical analysis

The queue configuration

• Specifies the number of queues
• Their location
• Effect on customer behaviour (balking or reneging)
• The max size the queue can hold (infinite/finite capacity)

Service mechanism

• Can involve one or several service facilities with one or several parallel service channelsThe service provided by a server is characterised by its service time
  
  • Typically involves data gathering and statistical analysis
  • Most analytical queuing models are based on the assumption of exponentially distributed service times

The queue discipline

• Specifies the order by which jobs in the queue are served
• Most common principle is FIFO
• Other rules are: LIFO, SPIT, EDD
• Can entail prioritisation based on customer type

Examples of world queuing systems:

Commercial queuing systems

• Commercial organisations serving external customers
• E.g. dentist, bank, ATM, petrol stations, plumber, garage …

Transportation service systems

• Vehicles are customers or servers
• E.g. vehicles waiting at toll stations and traffic lights, trucks or ships waiting to be loaded, taxi cabs, fire engines, lifts and buses

Business – internal service systems

• Customers receiving service are internal to the organisation providing the service
• E.g. inspection stations, conveyor belts, computer support …

Social service systems

• E.g. ER at a hospital, waiting lists for organ transplants, waiting lists for primary school places

Question 39

What are the advantages of multiple line queues vs single line queues

Answer 39

Multiple line vs single

Multiple:

• Service provided can be differentiated
• Labour specialisation possible
• Customer has more flexibility
• Balking behaviour may be deterred: several medium length queues are less intimidating

Single

• Guarantees fairness
• No customer anxiety regarding choice of queue
• Most efficient set up for minimising time in the queue
• Jockeying (queue switching) is avoided

Question 40

Explain the importance of variability in queuing

Answer 40

If there were no variability, there would be no need for queues to occur

Statistically, the usual measure for indicating the spread of a distribution is its standard deviation sigma.

However, variation does not only depend on standard deviation.

To normalise standard deviation, it is divided by the mean of its distribution. The measure it called the variation of the distribution.

Question 42

Explain Little’s Law

Answer 42

Question 43

What is the probability that there is n jobs in the system in a queue in the M/M/1 model.

Answer 43

Question 44

In the M/M/1 model what is:

Expected number of customers in the system

Expected time a job spends in the system

Expected number of customers in queue

Expected time a job spends in the queue

Answer 44

Question 45

What are the different shortage cost situations and how do you analyse design costs trade offs?

Answer 45

1. External customers arrive to the system

• Profit organizations
  
  • The shortage cost is primarily related to lost revenues “Bad Will”
• Non profit
  
  • The shortage cost is related to a societal cost

2. Internal customers arrive to the system
   * The shortage cost is related to productivity loss and associated profit loss

Usually it is easier to estimate the shortage costs in situation 2 than in situation 1.

Question 47

What is the common terminology for linear programming?

Answer 47

Question 48

What are the assumptions in linear programming?

Answer 48

• Proportionality
  
  • contribution of each activity Xj to the value of the objective function Z is proportional to the level of the activity Xj as represented by the CjXj term in the objective function. Similarly, the contribution of each activity to the left-hand side of each functional constraint is proportional to the level of the activity Xj, as represented by the AijXj term in the constraint.
• Additivity
  
  • Every function in a linear programming model (whether the objective function or the function on the left-hand side of a functional constraint) is the sum of the individual contributions of the respective activities.
• Divisibility
  
  • Decision variables in a linear programming model are allowed to take any values, including non-integer values, that satisfy the functional and non-negativity constraints.
  • Since each decision variable represents the level of some activity, it is assumed that the activities can be run at fractional levels.
• Certainty
  
  • The value assigned to each parameter of a linear programming model is assumed to be a known constant.

Question 49

Explain how to carry out project planning and control

Answer 49

Project planning and control

Stage 1: Understand the project environment

• Geo-social environment
  
  • Geography and national culture
• Econo-political environment
  
  • Economy and government
• Business environment
  
  • Customers, competitors and suppliers
• Internal environment
  
  • Company strategy, resources and other projects

Stage 2: Project definition

• Aim, strategy and scope

Stage 3: Project planning

• Objectives: what is the goal and estimate of cost/ time
• Project scope: how to approach, feasibility, major tasks
• Contract requirements: reporting and performance, responsibilities
• Schedules: activities, tasks, timelines, milestones
• Resources: budget and budget control
• Personnel
• Control: monitoring and evaluating progress and performance
• Risk analysis
• Identify activities
• Estimate the times and resources for activities
• Identify relationship and dependencies between activities
• Identify time and resource schedule constraints
• Fix the schedule for time and resources

Stage 4: Technical execution

Stage 5: Project control

• Earned value analysis
• Probabilistic analysis: program evaluation and review technique
  
  • Most likely time (m), optimistic time (a), pessimistic time (b)
  • Mean = a + 4m + b / 6
  • Variance = (b – a / 6) ^2
  • Use expected times to identify critical path, and compute slack and project time
  • Total project variance = Sum of variance of critical path activities
  • Project variance is a measure of the risk involved in the project
• Crashing project networks
  
  • Process of reducing time spans on activities so that the project is completed in less time.
  • Focus must be on critical path activities
  • In order to decide which activity to crash, the ‘crash cost slope’ of each is calculated (crash cost per time period).
  • Crash the activity on the critical path which has the lowest crash cost slope.

Question 52

Explain the max-flow min-cut theorem

Answer 52

Max-flow min-cut theorem

The theorem states that, for any network with a single source and sink, the maximum feasible flow from the source to the sink equals the minimum cut value over all cuts of the network.

Equivalently, optimality has been attained whenever there exists a cut in the residual network whose value is zero.

Question 53

What are the examples of some logical constraints?

Answer 53

Question 55

Describe the different between steady and transient state

Answer 55

Steady state condition

• Enough time has passed for the system state to be independent of the initial state as well as the elapsed time
• The probability distribution of the state of the system remains the same over time (is stationary).

Transient condition

• Prevalent when a queuing system has recently begun operations
• The state of the system is greatly affected by the initial state and by the time elapsed since operations startedas

Question 56

What is procurement, explain the difference between direct and indirect procurement

Answer 56

Means purchasing inputs used in the firm’s value chain

• Raw material
• Supplies
• Consumable items
• Assets such as machinery, lab equipment, office equipment, buildings

Direct purchasing: buying for primary activities

Indirect purchasing: providing supplies and services for support activities

Question 57

What are the different procurement strategies?

Answer 57

Performance based partnership

• High dependence on one supplier
• Used for strategic products

Competitive bidding

• In general, no long-term supply contract, rather multiple sourcing
• Used for interchangeable products

Securing continuity of supply

• Securing supply of bottleneck products, if necessary, at additional cost
• Reducing dependence on supplier by developing alternative products and looking for alternative suppliers

Category management and e-procurement solutions

• MRO (maintenance, repair, operating supplies) products require a purchasing strategy which is aimed at reducing administrative and logistic complexity
  
  • Electronic catalogues
  • Article catalogue (standardisation of product assortment)

Question 58

Plot purchasing’s impact on financial results vs supply risk

Answer 58

Question 63

What is Operations Research? Give examples of the different types

Answer 63

OR professionals aim to provide a rational basis for decision making by seeking to understand and structure complex situations and to use this understanding to predict system behaviour and improve system performance.

Done using analytic and numeric techniques to develop and manipulate models of organisational systems.

Types of OR models

• Linear programming: objective function and constraints are all linear functions of the decision variables
• Network flow programming: special case of linear program where situation can be modelled as a network
• Integer programming: variables are required to take integer values
• Non-linear
• Dynamic programming: process described in terms of states, decisions, transitions and returns. Problem is to find sequence that maximises total return.
• Stochastic programming: Uses random variables for some aspects of the problem. Expression can be written for the expected value of the objective.

Question 64

Explain the centre of gravity approach

Answer 64

Question 65

What are the benefits of supplier collaboration and government?

Answer 65

Organisation benefits

Increased performance:

• Access to innovation
• Improved customer satisfaction
• Better quality
• Improved on time delivery
• Increased responsiveness

Lower risk:

• Less SC disruption
• Less reputational damage
• Less product scarcity
• Fewer delayed responses to crises

Supplier benefits

• Lower operational cost
• Motivation to innovate
• Increased efficiency
• Better planning

Mutual benefits

• Product development time shortening
• Quality improvements
• Cost reduction
• Smooth release of new product
• Value co creation

Question 66

What are the different types of supplier relationships?

Answer 66

Question 67

What are the different collaboration techniques?

Answer 67

Just in time

• When products are delivered when they are needed.

Vendor managed inventory

• When suppliers take responsibility for a range of contracts to manage the buyer’s inventory. A method introduced to cope with bull-whip effects.

Collaborative planning, forecasting and replenishment

• When supply chains become integrated. CPFR seeks cooperative mgmt. of inventory through joint visibility and replenishment of products throughout the supply chain.

Question 69

How do you categorise and evaluate supply partners? What are the challenges for partnership building in terms of collaboration, government and sustainability

Answer 69

Categorise existing and potential suppliers as:

Strategic

Suppliers important for the buying firm in the sense that they provide the buying firm with essential material and capabilities that cannot be substituted

Preferred

Suppliers that could be replaced, with some effort, in the long-term.

Transactional

Suppliers that can be easily replaced in the short-term

Evaluation criteria: price, delivery, quality, production capability, localisation etc.

Question 70

What is procurement?

Answer 70

Procurement is an auction:

• Requirements for the next performance period
• Communicate to suppliers (bidders)
• Suppliers submit a bid (first price, sealed bids)
• The procurement team chooses the winning bidder

Procurement, logistics, inventory mgmt. and production control are tightly linked

In some markets, 80% of product revenues is directed to suppliers for labour, material and equipment

Question 71

Explain the importance of supplier evaluation in procurement and draw the procurement iceberg

Answer 71

• Market requires product and service quality at reasonable prices. Depends highly on production and suppliers.
• Suppliers are being selected based on their value-added capabilities.
• The buying firm has to determine
  
  • Product/service attributes
  • Expected requirements and
  • Right quality at reasonable price

the process:

1. Identify key purchasing
2. Determine puchasing strategy
3. Identify potential sources
4. Limit supplier in pool
5. Determine method of evaluation
6. Make selection

Question 72

Explain the different methods of supplier evaluation (procurement)

Answer 72

• Process-based evaluation
  
  • Evaluation based on suppliers’ production or service processes.
• Performance-based evaluation
  
  • Evaluation based on (objective) performance measures
  • Examples:
    
    • Categorical
    • Cost Ratio
    • Weighted point (linear averaging)
• Value based sourcing:
  
  • Can the supplier decrease our risk (e.g., reducing bottlenecks/critical parts purchasing; disruption response; exchange rates)?
  • Can the supplier provide some other competitive advantage (e.g., differentiating factor; new product variant)?
  • Can the supplier help expand the portfolio to address new customer needs?

Categorical method

• Categorization of every supplier, in specific areas, based on a pre-defined list of performance variables.
• Categorical assessment, e.g. ‘good’, ‘neutral’, ‘unsatisfactory’.
• Easy to implement, minimal data required, low-cost
• Lacks reliability, subjective, manual process

Cost ratio method

• Categorization of every supplier by standard cost analysis.
• Rating performance at each performance factor.
• Specific underperformance areas are identified, objective supplier ranking, long-term improvement potential, comprehensive assessment
• Cost-accounting required, complex process, information technology resources required

Weighted-point method

• Categorization of every supplier by weights on a list of performance variables.
• Flexible system, supplier ranking, moderate capital costs, combines qualitative and quantitative factors
• Tendency to focus on price, information technology resources required

Question 74

Describe the algorithm for shortest path problem

Answer 74

Objective of the nth iteration:

• Find the nth nearest node to the origin

Input to the nth iteration:

• n-1 nearest nodes to the origin, including their shortest path and distance from the origin. (These nodes, plus the origin, will be called solved nodes)

Candidates for the nth nearest node:

• Each solved node that is directly connected by a link to one or more unsolved nodes provides one candidate – the unsolved node with the shortest connecting link to this solved node. (Ties provide additional candidates).

Calculation of the nth nearest node

• For each such solved node and its candidate, add the distance between them and the distance of the shortest path from the origin to this solved node. The candidate with the smallest such total distance is the nth nearest node (ties provide additional solved nodes), and its shortest path is the one generating this distance.

Applications

• Minimising the distance travelled
• Minimising the total cost of a sequence of activities
• Minimising the total time of a sequence of activities

Question 75

Explain why a changing world creates supply chain risks? Give examples of supply chain risks

Answer 75

OEM:

• Vertical integration vs specialisation
• Integral products vs modular assembly
• Centralised vs dispersed

Unpredictable environment

Changing technology landscape

Increasing dependence on suppliers and subcontractors

Implications for future

• Value chains are increasingly fragmented and complex
• Competition between global supply chains
• Managing uncertainty is a key requirement
• Emergence of new business models

Question 76

What are the different types of supply chain risks?

Answer 76

• R&D risk
  
  • Management
  • Product /process design and technology
  • Skill set
• Procurement risk
  
  • Supplier relationship
  • Raw material
  • Location
• Production risk
  
  • Management
  • Product, process technology
  • Location
• Distribution risk
  
  • Management
  • Product
  • Location
• Sales and marketing risk
  
  • Management
  • Demand projection
  • Location

Question 77

What are the two approaches for supply chain risk evaluation and management?

Answer 77

Two approaches for supply chain risk evaluation and management

1. Traditional

• Identify supply chain characteristics
• Identify risks linked to these
• Evaluate risks (impact and probability)
• Choose mitigations
• Evaluate impact of mitigations
• Plan mitigations
• Monitor risks and risk mitigation

Risk:

• Identification
• Assessment
• Mitigation
• Monitoring

2. Configuration approach

Mapping SC:

• Network structure
• Process flow
• Value structure
• Product characteristics

Event:

• Characteristics
• Database

Identifying risks

• Overlaying event data on SC map
• Identification of vulnerability led risk

Mitigations

• Change in network structure
• Alternative process flow
• Adjusting value structure
• Product redesign

Question 78

Draw the supply chain resilience framework

Answer 78

Question 79

What are the different supply chain risk mitigation strategies?

Answer 79

Risk mitigation strategies:

• Increase capacity
• Acquire redundant suppliers
• Increase responsiveness
• Increase inventory
• Increase flexibility
• Pool or aggregate demand
• Increase capability

Question 80

How do you calculate population and sample:

Mean

Standard deviation

How do you find the outliers when cleaning data?

Answer 80

Question 81

What are the assumptions of the mean square linear regression model?

Answer 81

Model assumptions:

Mean of zero: at any given value of x, the population of the error term values has a mean equal to zero

Constant variance assumption: at any value of x the population of the potential error term values has a variance that does not depend on the value of x

Normality assumption: At any given value of x, the population of potential error term values has a normal distribution. If this assumption holds, a histogram of residuals should look bell and symmetric

Independence assumption:Any one value of the error term is statistically independent of another.

Question 82

Describe the mimimum spanning tree algorithm and its applications in the real world

Answer 82

Algorithm to solve the MST problem

1. Select any node arbitrarily, and then connect it to the nearest distinct node
2. Identify the unconnected node that is closest to a connected node, and the connect these two nodes. Repeat this step until all nodes have been connected.
3. Tie breaking: Ties for the nearest distinct node (step 1) or the closest unconnected node (step 2) may be broken arbitrarily, and the algorithm must still yield an optimal solution. However, such ties are a signal that there may be (but need not be) multiple optimal solutions. All such optimal solutions can be identified by pursuing all ways of breaking ties to their conclusion.

Applications of the MST problem

• Design of telecommunication networks
• Design of a lightly used transportation network to minimise the total cost of providing the links
• Design of a network of high voltage electrical power transmission lines
• Design of a network of wiring on electrical equipment
• Design of a network of pipelines to connect a number of locations

Question 83

Explain the augmenting path algorithm

Answer 83

An augmenting path is a directed path from the source to the sink in the residual network such that every arc on this path has strictly positive residual capacity. The minimum of these residual capacities is called the residual capacity of the augmenting path because it represents the amount of flow that can feasibly be added to the entire path.

1. Identify an augmenting path by finding some directed path from source to sink in the residual network such that every arc on this path has strictly positive residual capacity. (if no augmenting path exists, the net flows already assigned constitute an optimal flow pattern)
2. Identify the residual capacity c* of this augmenting path by finding the minimum of the residual capacities of the arcs on this path. Increase the flow in this path by c*.
3. Decrease by c* the residual capacity of each arc on this augmenting path. Increase by c* the residual capacity of each arc in the opposite direction on this augmenting path. Return to step 1.

Some applications of the maximum flow problem

• Maximise the flow through a company’s distribution network from its factory to its customers
• Maximise the flow through a company’s supply network from its vendors to its factories
• Maximise the flow of oil through a system of pipelines
• Maximise the flow of water through a system of aqueducts
• Maximise the flow of vehicles through a transportation network

Question 84

What are the different types of machine learning?

Answer 84

Machine learning

• Supervised learning
  
  • Here is the data set where the right answers are given for each example. Please produce more right answers.
  • Classification
• Unsupervised learning
  
  • Here is the unlabelled data. Please find peculiarities, similarities or structures (clusters) in the data yourself
  • Association rule learning
  • Clustering
• Reinforcement learning
  
  • Learn to do something by maximising your reward

Question 85

Explain classification: give examples

Answer 85

• Aim: to label data
• Create a model that predicts what class label new data should have
• Model must first be trained by providing examples
• Examples: classify suppliers, predict condition of engineered parts, classify customers purchasing habits

Various different algorithms for classification:

• Tree induction
• Bayesian
• Rule based

Question 88

What does a neural network look like?

Answer 88

Question 89

How do you calculate weights in a neural network?

Answer 89

Question 90

What is the activation function?

Answer 90

Question 91

How do we assess the performance of a neural network and how do we improve that performance for each iteration

Answer 91

2. Evaluation: How do we assess how well the network performs?

• Initialise with random weights and biases
• Show the network a training example
• Network calculates the activations of all neurons of all layers (using initial weights and biases)
• And then we can compare the value of each output neuron with the value we actually wanted and compute the squared error for each neuron
• This is done for all neurons in the output layer and sum up the squared errors
• So far this was the error for a single image. So, we do the whole process for ALL thousands of training examples
• Then we take the average error for each training example

3. Optimisation: How do we tell the network how it can improve its performance?

• We know how to find the minimum
• We calculate the derivative, set it to zero
• Then we get the point and check if it is a global minimum or not

Gradient descent

• You start anywhere on the (multi-dimensional) cost function: random initialisation
• You “look” into all directions from the point of where you are and determine the direction with the steepest descent: you calculate the negative Gradient (the direction of steepest descent)
• You then move one step into that direction
• The step size (or “learning rate”) matters
• The negative gradient of the cost function tells us how to adjust our weights to take the next step

Question 92

How do you develop a simulation model?

Answer 92

• Understand model goals
• System analysis
• Model and simulation specification
• Model verification and validation
• Design and run experiments
• Draw inferences

Question 93

Why is manufacturing servitising?

Answer 93

Economic rationale:

• Manufacturing firms in developed countries cannot compete on cost
• Installed base argument
• for every new car sold there are already 13 in operation, 15 to 1 for civil aircraft and 22 to 1 for trains
• Stability of revenues – service vs products

Strategic rationale:

• Lock in customers
• Lock out competitors
• Increase the level of differentiation
• Customers demand it
• Service as a pre-sale activity

Environmental rationale:

• Environmental rationale

Question 94

What are the seven principles of service design?

What are the phases of service design thinking?

Answer 94

What are the seven principles of service design?

1. Bias toward action
2. Embrace experimentation
3. Radical collaboration: bring together innovators from varied backgrounds
4. Show don’t tell: communicate by creating experiences
5. Focus on human values: understand the people you are designing for and get feedback
6. Craft clarity: produce a coherent vision
7. Be mindful of process: know where you are in the process and what your goals are

The phases of service design thinking

Empathize

• Observe, engage, immerse

Define

• Define your point of view
• Provides focus, reference for evaluating ideas, fuels brainstorming

Ideate

• Ideate to step beyond the obvious solutions and drive creativity

Prototype

Test

Question 95

Show the examples of servitisation for Zoelis, GEA and Pearson and compare them

Answer 95

Question 96

Explain the key facts about the service journey

Answer 96

Findings show that the service journey occurs:

• Small, careful and incremental changes
• At different organisational levels
• The 4th year is crucial. Two concurrent steams of service development:
  
  • Continue to build up on current basic and intermediate services
  • Exploration and piloting of more complex services

Question 97

What are the seven critical success factors for service transistion?

Answer 97

Seven critical success factors:

Assess market and internal readiness

Creating the strategic and cultural context:

• Design service vision
• Define customer mindset and engage partners
• Develop service culture

Structures and governance

• Define leadership, set organisational structure

Resources

• Define company and individual resources

Engagement and trust

• Engage customer mindset, partners
• Enable change

Service processes

• Design and plan service model
• Pilot and model
• Portfolio mgmt.
• Commercial execution

Optimise and communicate best practices

Question 98

What is a supply network?

Answer 98

Supply Network: A set of connected but geographically dispersed firms involved in making and delivery of product/service to end customers

Question 99

What are the different supply network decisions?

Answer 99

Strategic

• investment in plants: numbers, locations
• introduction of new products: BOMs used
• manufacturing technology
• creation of logistics network
• make vs buy, supplier selection

Tactical

• manufacturing system
• inventory policy
• procurement policy
• IT system and information flow
• customer strategies, demand planning, forecasting

Scheduling of resources (labour, machine, vehicles)

Routing of raw materials and finished products

Solicitations of bids/quotations, order processing

Question 100

What technologies are impacting Digital Manufacturing today?

Answer 100

What technologies are impacting DM today?

Sensing: non industrial sensing, network many devices, vision, AR, VR, crowd sourced data

Analysis: cloud computing, mobile computer, clustering algos

Decision: Machine learning, smart products, optimisation, low cost computing

Actuation: Cobots, customers in the loop, AM, FPGAs

Question 101

What is industry 4.0 what is the rationale what are the dimensions?

Answer 101

Industry 4.0

What is it:

framework for enabling the intelligent integration of physical and digital resources, services and humans resources in manufacturing in real time.

Rationale:

strong individualisation of products, flexible production, hybrid (servitisation)

Dimensions:

Vertical integration and networked manufacturing systems

Horizontal integration through value networks

End-to-end digital integration of engineering across the en3re value chain

Question 104

Describe using examples, the terms vulnerability, risk and resilience in the context of supply chains.

Answer 104

• The supply chain risk and resilience framework explains the concept of event, vulnerability, risk and resilience.
• At its centre is ‘event’ (such as climate change, war, new regulation or financial crisis), which might have significant impact on supply networks.
• Next is ‘vulnerability’, which is associated with structure of supply network and particularly its lack of flexibility.
• ‘Risk’ appears when key events and vulnerability interacts with each other, which leads to supply network failure.
• Next is ‘risk mitigation’, which is an action or set of actions taken by companies to minimise either impact or changes (probability) of risk.
• ‘Resilience’ is an ability to recover from network failure, which is achieved by continuously changing supply networks in response to risks by using risk mitigation approaches, such as adopting new processes and /or practices or by reconfiguration

Question 106

How do you choose a sourcing strategy?

Answer 106

Single vs. multiple sourcing

• Assessment with regards to dependence, supply risk and transaction costs

Global vs. local sourcing

• Local sourcing preferred when product is a high-tech product for which specification often changes; high flexibility and precision required in terms of delivery

Partnership or competitive relationship

• Competitive relationship mostly used when commodities are purchased, when the products are purchased in in large volumes and when many suppliers are available

Buying on contract or buying on spot basis

• Contract buying preferred when prices are expected to rise
• Advisable to choose a mix between contract and spot buying

Price agreement vs. performance agreement

• Performance agreement often used when services are purchased (Service level agreement)
• Price agreements might be sufficient if standard quality products are purchased (for example certain types of fabric)

Question 107

What is the objective of locations strategy? What factors impact how it is picked?

Answer 107

Objective of location strategy: to maximise the benefits of location to the firm

Location decisions can be determined by:

• Marketing strategy
  
  • Compete on cost: find low cost location
  • Compete on level of responsiveness: close to transportation networks/market
• Cost of doing business
• Growth
  
  • Potential access to more customers
  • Expanding product portfolio
• Depletion of resources
  
  • Industries where resources determine key success

Factors influencing location decisions

• Economic
  
  • Tariffs, taxes, trade concession, capital subsidies
• Temporal
  
  • Competition, demand patterns, industry dynamics, presence of related industries (clustering), skilled employees’ engagement
• Physical location
  
  • Labour cost, developed infrastructure, proximity to market, cost of inputs, competitors locations, specialised inputs
• Organisational factors
  
  • Strategic role of a factory amongst multiple plants

Question 108

Why do companies go abroad? What should they consider?

Answer 108

• M&A
• Business growth
• Faster lead times/cost reduction
• Increase of offshoring

Aspects countries should consider:

• Country level
  
  • Political risks, legislation, economic issues (currency), location, labour, availability of suppliers
• Region level
  
  • Labour, cost, regulations, proximity to resources, land cost
• Site level
  
  • Site size/cost, distribution systems, proximity to suppliers, environmental impact, clustering

Question 109

Why are location decisions so important?

Answer 109

Irreversible allocation of the firm’s capital – long term/strategic decision

Business continuity

Impact on supply chain performance

• Lead times
• Inventory
• Responsiveness to demand
• Flexibility
• Quality

Question 110

What are the different causes of uncertainty in a supply chain and how do they affect the SC

Answer 110

Causes:

• Labour
• Natural disasters
• Machinery
• Power grid shutdown
• Foreign exchange
• Demand:
  
  • arises from volatile demand or inaccurate forecasting
• Raw material availability and price
• Supply:
  
  • caused by variability of supplier’s performance e.g. defective deliveries
• Process:
  
  • results from the unreliability of the production process due to e.g. machine breakdown, employees underperformance, wrong methods used

Question 115

What is supply chain sustainability?

Answer 115

Supply chain sustainability is the management of environmental, social and economic impacts, and the encouragement of good governance practices.

The boundary of responsibility often extends beyond the reach of a corporation’s ownership and control

Aim is to achieved traceability and transparency of SC through supplier collaboration

Traceability:

• Identification of better sources of raw materials, compliance with internal law standards and certification
• A tool to build a reputation for supplying high quality products

Question 120

What are the different inventory types and motives for keeping inventory? What are the attributes of an inventory system (cost and demand)?

Answer 120

Inventory types:

• Raw materials
• WIP
• Finished goods

Motives for keeping inventory:

• Economies of scale
• Uncertainty
• Speculation
• Transport
• Smoothing
• Logistics
• Cost control

Attributes of inventory systems:

Demand:

• Stable or variant
• Deterministic or stochastic
• Lead time
• Review time
• Periodic review
• Continuous review
• Lost sales

Cost elements:

• Holding cost
• Order cost
• Penalty cost

Question 121

What are the key concepts that make up supply chain risks?

Answer 121

Key concepts that make up supply chain risks

Events:

• Occurrence happening at a determinable time and place, with or without the participation of human agents
• Financial shock, trade dispute, geopolitics, natural disaster, disease

Vulnerability

• Inability to withstand the effects of an event.

Uncertainty

• Uncertainty related to a known event (risk) and uncertainty related to an unknown event (pure uncertainty)

Risk

• Chance of event happening that will have negative or positive consequences
• Risk is made up of uncertainty, impact, context and nature
• Probability of an event x impact of that event

Resilience

Question 129

What are different goodness of fit test?

Answer 129

The Chi square test

• Involves comparing the histogram to a discretised pdf of the fitted distribution.
• The higher the p value or the lower the test statistic the better the fit.
• A disadvantage of this test is arbitrariness in the binning and different bins give different answers
• For this reason this statistic should only be used when the distribution being tested is discrete.

Kolmogorov-Smirnov

• KS statistic is to compare the cdf of the fitted distribution and the cdf of the sample data by taking the max vertical difference between them.
• In general, the lower KS the better the fit.
• KS < 0.03

Anderson-Darling

• AD statistic weighs the squared distance between the fitted and observed distribution
• In general, the lower AD the better the fit.
• AD < 1.5

Criteria information tests can help make decisions

• BIC and AIC

Question 130

What are data analytics and why do we need it?

Answer 130

Data analytics is…

• The extensive use of data, statistical analysis, and predictive models to drive decisions and actions.

Analytics has long existed in manufacturing firms:

• Total quality mgmt.
• Statistical analysis for product quality

Increasingly used in all areas of manufacturing…

• Which supplier
• How should supply chain be configured
• Best sales channel
• How are products used
• What product configurations

Question 133

Explain association rule learning: give examples

Answer 133

Aim

• To find interesting associations between data values
• Based on the frequency that values appear together
• It only finds whether associations exist or not- it does not indicate why there is an association

Examples: detecting when manufacturing equipment needs maintenance, detecting what is causing a defect in a product, logistics

Metrics:

• Support: how pervasive is the rule?
  
  • the rule appears in 50% of all the transactions
• Confidence: how certain is the rule?
  
  • for transactions containing chips (premise), the rule is correct 75% of the time

Question 134

Explain clustering: give examples

Answer 134

Aim:

• To group data into classes or “clusters”
• (so that items in the same cluster have a high similarity to one another but are dissimilar to items in other clusters)
• Useful to discover features that distinguish groups
• Useful as a pre-processing step for classification: to automatically determine labels
• The class labels are discovered by clustering and therefore do not need to be provided
• Examples: identify factors that distinguish customer types, identification of products that are returned, determine what machines develop faults

Main methods

• Partitioning methods (k means)
• Hierarchical methods
• Density based methods
• Grid based methods
• Model based methods

Question 145

What is DM, why digital manufacturing, why now?

Answer 145

The application of digital information [from multiple sources, formats, owners] for the enhancement of manufacturing processes, value chains, products and services

Why DM

• Cost
• Time
• Labour
• Manage complexity
• Better customer service
• Quality

Why now?

• Sensors
• Tech (AI, cloud, data analytics)
• Globalisation (global supply chain)
• Flexible product demand
• Product service demand

Question 146

What are today’s manufacturing challenges?

Answer 146

Making things cheaper, faster, better

• Increased productivity
• Material & energy sustainability
• Resilience to change/disruption mgmt.

Making things in different ways:

• Distributed production: network of geographically dispersed manufacturing facilities that are coordinated using information technology.
• Late customisation
• Near customer manufacturing
• Specialised

Manufacturing in new areas

• Production at retailer, the farm, the construction site, home

Manufactured product and service blending

• Aircraft operational services
• Customised logistics
• Hospital support services
• Appliance repair services
• Non production operations with resource constraints, cost thresholds, quality targets etc

Summary

• more productive, sustainable, resilient, etc
• distributed, specialised, customised, localised
• Production in a remote / mobile / small scale / one off manner

Question 149

Describe six supply chain risk mitigation strategies. Explain possible unintended consequences of supply chain risk mitigation, using examples.

Answer 149

Supply Chain Risk Mitigations:

• Increase capacity
  
  • Build centralised capacity for unpredictable demand
  • Build decentralised capacity for managing supply chain disruptions due to natural disasters
• Acquire redundant supplier
  
  • Favour more redundant supply for high volume products, less redundancy for low volume product
  • Centralise redundancy for low volume products in a few flexible suppliers
• Increase responsiveness
  
  • Favour cost over responsiveness for commodity products
  • Favour responsiveness over cost for short life products
• Increase inventory
  
  • Decentralise inventory for predictable, low value products
  • Centralise inventory for unpredictable, high value products
• Increase flexibility
  
  • Favour cost over flexibility for predictable, low volume products
  • Favour flexibility for low volume, unpredictable products
  • Centralise flexibility in a few locations if it is expensive
• Increase capability
  
  • Prefer capability over cost for high value, high risk products
  • Favour cost over capability for low value, commodity products
  • Centralise high capability in flexible source if possible

Unintended consequences of supply chain mitigations

• Adding capacity increases cost of operation. High capacity cannot be sustained in the long run if there is perfect competition
• Increasing inventory increases cost of operation.
• Having redundant suppliers increases cost of operation.

Question 150

Compare and contrast the traditional and the configurational approach to supply chain risk management.

Answer 150

Traditional approach of supply chain risk management:

• Identifying Supply chain risk characteristics
• Identifying risks linked to supply chain characteristics
• Evaluate risks
• Choose relevant risk mitigations
• Evaluate impact of chosen mitigation
• Plan mitigations
• Monitor risks and risks mitigation

Configuration approach of supply chain

• Mapping Supply chain : Including network structure, process flow, value and product characteristics
• Understanding event: characteristics and database
• Identifying risks: overlaying event data on SC map and identification of vulnerability led risk
• Mitigations: Change in network structure, alternative process flow, value adjustment and product redesign

Question 151

Explain the rational approach for an automation project including integration

Answer 151

Rational approach

Define the challenge – create a specification

• To arrive takes time (supplier, client and third party’s) effort, money, patience
• Single biggest success/failure factor
• Should cover all functionality, is unambiguous, promotes common understanding

Identify risks

• Manage risk by prototyping, consulting and work on risk areas early
• Preparation, build (mechanical, electronic, software) and project (human, interface, supplier) errors
• Failure mode and effects analysis

Generate alternative solutions, evaluate and select

• Postpone the selection, evaluation and gather proposals from a wide variety of sources
• Evaluation criteria: technical, practical, timing, commercial, legal, organisational, environmental

Plan

• Specify, design, procure, build, integrate, test
• Break jobs into small tasks, visible milestones, design reviews, iterative development
• Actively look for problems, risks that you understand can be managed

Implement, commission and test

• Integration problems: hardware, software, electrical, interfacing problems (mechanical fit, sensor abilities, robot reach)
• Incremental innovation is better
• Incremental delivery
• Test elements one at a time, step through cycle

Question 153

What is a PLC?

Answer 153

A class of industrially hardened devices that provides hardware interface for input sensors and output actuators, PLCs can be programmed to control the outputs based on input conditions and/or algorithms contained in the memory of the PLC

consists of:

• A CPU (central processing unit )
• Memory for software and data (built in or removable)
• Input/output system to allow physical connection to field devices (e.g., switches, sensors, etc.), both digital and analogue

Question 154

What is a fixture? What is the functions of a fixture?

Answer 154

A fixture is a mechanical device that can be used for locating a part repeatedly in a known position and clamping it securely, so that work can be performed on it.

Functions of a fixture:

• Location
  
  • Positioning and orienting a workpiece for an operation
  • Repeatability
  • Ease of use
  • Allow access for operations
• Clamping
  
  • Holding a workpiece securely during an operation
  • Adequate clamping force
  • Reliable clamping force
  • No part distortion
  • Workpiece security
  • Correct clearance

Other fixture design criteria:

• Poka Yoke
• Quick Change: SMED
• Flexible

Question 155

What are the benefits of modular cell control?

What are issues to consider in cell control?

Answer 155

Modular design of production control code:

• Reconfigurable production
• Manageable module development
• Ease of testing and debugging
• Customisation capability

Issues to consider:

• Requirement to link product to customised recipe
• Capability of tracking the product through the production process
• Track the status of the product as it moves through production
• One way is to use RFID

Question 156

Who is important in testing a new automated production system?

What are the key milestones

Answer 156

System integrators:

• Equipment vendors
• Software vendors
• Sub system vendors

End user:

• Operators maintenance
• Management team
• Facilities

Question 157

What does unit testing comprise of?

When should unit and system testing be carried out?

Answer 157

Unit testing:

• Throughout production component development
• Test functionality
• Operational status
• Error conditions
• High level interface

System testing:

• When modules of production components are ready
• Hardware interfaces
• Software interface (hand shaking)
• Error/recovery strategies

Question 158

What are the different types of switches and their applications?

Answer 158

Precision position switch

• A range of high precision measuring and control switches.

Inductive proximity switch

• The inductive proximity switch consists of a coil wound around a ferrite core at the sensing head
• High freq. is applied to coil to generate an oscillating magnetic field
• When metallic object travels towards field eddy currents are generated reducing oscillation freq.

Applications:

• Missing washer can be detected
• Check metal is right thickness
• Check screws have been correctly tightened
• Metal components counted as they fall from a bowl feeder
• Can detect machine table at its limit

Capacitive proximity switch

• Current sourcing proximity switch
• Capacitive switch is mounted below a plastic area above which product passes. Sensor is tuned to detect the presence of the target object.

Application:

• Sense liquid in plastic tank

Optical proximity switch

An optical proximity switch which senses return light from target surface

Optical through beam sensor:

• Emitter and receiver
• Detecting milk in cardboard cartons
• Sense label presence

Optical retro-reflective:

• Range of retro reflective sensor can be adjusted, allowing thresh holds to be set.
• With no object all light is reflected 100%
• With object near the reflector nearly all light is reflected
• Check the presence of a label

Optical retro reflective (polarised)

• Shiny metallic objects, cuts out ambient reflected light

Pressure sensor:

Sensing element is silicon diaphragm, integral to the IC chip.

Question 159

What is IoT?

What is industrial internet of things?

Answer 159

Internet of things is the network of physical devices, vehicles, home appliances, and other items embedded with electronics, software, sensors, actuators and network connectivity which enable these objects to connect and exchange data.

What is industrial internet of things?

The application of IoT to create value for industrial processes, supply chains, products and services?

Question 160

When could industrial IoT be useful?

Answer 160

• Integrating data from suppliers, logistics, providers, customers
• Introducing new technology, peripherals, tools, equipment
• Distributed production requiring addition of new data sources, locations, owners
• Sensors on board raw materials, parts, products, orders passing through organisation

Security, privacy/data IP, benefits are challenges

Question 161

What is an end effector? What are typical end effector tasks?

Answer 161

End effectors:

• An end effector is a device at the end of a robot arm that is used to perform some task. (Gripper, Welding head)
• The robot is used to orientate and move the end effector into the required position.
• Typically, the operation of the end effector is controlled by the robot controller.

Typical tasks end effectors perform:

• Gripper, Drill, De-burring, Sanding, Nut spinner, Laser welder, Sucker gripper, De-burring
• Maintaining part location and accuracy
• During the assembly operation it’s critical to consider the total accuracy and repeatability parameters of the production environment.
• Accuracy and repeatability

Question 164

What are the different types of automation?

Answer 164

Automated solutions can be considered to be:

Dedicated automation: designed to carry out one specific task

• High speed operations, solution optimised for specific need
• Can’t handle product variations, equipment cannot be re tasked for other activities

Flexible automation: designed to carry a variety of tasks

• Can handle product variations, make use of standard equipment, payback across multiple product variations, equipment can be re-tasked to other activities
• Complexity of solution, operational times can be slower, solution can be expensive

Question 167

What are the different types of robots? What are their features and applications

Answer 167

Anthropomorphic robot

Features:

• Typically, six axis configurations
• Flexible, can reach points in multiple configuration

Applications:

• Used for welding, painting, machine loading, assembly, etc

Selective compliance assembly robot arm (SCARA)

Features

• Typically, four axis configurations
• Two link, cylindrical robot
• Flexible, can reach points in multiple configurations

Applications

• Used for high speed assembly, kitting, packaging, and other material handling applications

Delta robot

Features

• Typically four, five or six axis configuration
• Parallel robot (multiple actuators working together in parallel)
• High speed operation
• Constrained work space

Applications:

• Used for material handling of light weight products for packaging and assembly

Cartesian robot

Features

• Typically four, five or six axis configuration
• Linear or gantry robot (multiple axis at right angles to each other working in straight lines)
• Robot control is simplified due to the use of linear rather than rotary axis

Applications

• Used for CNC machining, machine loading, packaging and assembly.

Question 169

Compare the different robot teaching techniques?

Answer 169

Question 171

Compare CNC and AM

Answer 171

CNC

• Repeatable
• Precise
• Good surface finish
• High productivity
• Waste material
• Limited work piece figure

AM

• Less material wastage
• Geometrical freedom
• Material options
• Metallurgical bond
• Long cycle time
• Poor surface finish

Question 172

What is automation?

Answer 172

• “the use or introduction of automatic equipment in a manufacturing or other process or facility” Oxford dictionary
• The creation and application of technology to monitor and control the production and delivery of products and services. Automatic federation

The replacement of man by machinery:

• Physical actions
• Data gathering
• Decision making

Mode of operation where a machine or piece of equipment is capable of working without human intervention.

Question 173

What are the benefits and challenges of automation?

Answer 173

Benefits:

• Improved working environment
• Increased production rate
• Improved product quality
• Reduce scrap and rework costs
• Improve factory floor space utilisation
• Reduce manual paper-based tracking / scheduling processes

Challenges:

• Complexity of tasks to be automated out
• Production rates to be achieved
• Exception handling
• Skills required to run production facility
• Payback on automated solution
• Catering for product change and variation

Question 174

What are the pros and cons of the SCARA robot?

Answer 174

SCARA

PROS

• Ideal robot type for inserting screws into holes. Stiff in the Z Axis but compliant in X,Y.
• Due to its stiffness in the Z axis it can apply significant loads in the Z axis. This is essential when inserting self-tapping screws.
• Best repeatability of the different robot types on the market, making it ideal for the placement of small screws in an electronic assembly.
• Some of the fastest robots on the market, allowing it to easily service operations from the two lines and a screw feeder.

CONS

• Limited working volume, but easy to visualise for a 2D space
• Working volume is cylindrical in nature, complex to utilise.
• Payloads can be limited if full operating speeds are required.

Question 175

What are the pros and cons of the Cartesian robot?

Answer 175

2. Cartesian

PROS

• The Cartesian style of robot can carry out fastening type operations.
• Cartesian robots are made up from linear axis and can provide large working volumes
• Cartesian robots can support significant payloads, suitable for the operation of an electric screwdriver
• Cartesian robots have good repeatability, making them suitable for electronic assembly operations

CONS

• It has limited compliance in the X,Y plane.
• Cartesian robots tend to be the slowest of the different robot types. It may not be possible to meet the takt time required in servicing the two phone lines.

Question 176

What are the pros and cons of the anthropomorphic robot?

Answer 176

3. Anthropomorphic

PROS

• Very flexible robot, capable of working in a number of planes. (Not required in this application)
• Can be re-tasked or have its role extended to other tasks easily.

CONS

• Stiffness in the Z axis is limited. This is due to limited torque available in the wrist axis.
• Complex working volume that is spherical in nature.
• The anthropomorphic is one of the slowest robots.
• The repeatability of the anthropomorphic robot is mid-range and may need to be examined closely for applications in electronic assembly.

Question 177

What are the pros and cons of the Delta robot?

Answer 177

Delta

PROS

• The Delta robot has good repeatability required for electronic assembly.

CONS

• The working volume of the work space is limited in the Z Axis. Challenging to accommodate screwdriver operations.
• Payloads on the Delta robot is limited and not suitable for screwdriver operations.
• The Delta robot doesn’t have the appropriate stiffness in the Z Axis to support fastening type operations.

Question 179

Why are robots used in flexible automation solutions?

Answer 179

• A robot can provide a flexible piece of automation hardware
• Robots of varying capabilities can be purchased and quickly configured to an application’s needs
• Operational tasks can vary depending on production requirements
• Operational tasks can be updated as future production requirements are identified
• Robots can be easily integrated into factory control systems
• Robots can be re-tasked to different automation solutions over time

Question 180

Define a robot?

Answer 180

Definition of a robot

“a re-programmable device designed to both manipulate and transport parts, tools or specialised manufacturing implements through variable programmed motions for the performance of specific manufacturing tasks.”

Applications:

• Arc welding
• Cut, grind, debur, polish
• Palletising, packaging
• Spot welding
• Handling
• Loading
• Handling, deburring
• Unloading
• Painting
• Assembly

Question 182

What are the robot performance measures?

Answer 182

Robot performance measures:

• Working volume
• Payload (max mass a robot can manipulate at a specified speed)
• Speed
• Resolution (amount of joint motion required to be a recognised change in sensed position)
• Accuracy (deviation between commanded and attained position)
• Repeatability

Question 184

Define pneumatics?

What are the pros and cons of using air?

Answer 184

Pneumatics: definition

Systems operated with air or gaseous medium to impart power or to control power

Compressed air pros & cons

• Availability: most factories have supply
• Elasticity: can be stored in containers
• Safety: not a fire hazard
• Reliability: components have long working life
• Clean technology
• Resistance to environment … heat, cold, dirt, corrosion
• Economy: low installation and maintenance cost
• Choice of movement: linear, angular, rotary, gripping
• Expensive!!

Question 185

Explain different types of valves and actuators

What other equipment is used

Answer 185

Valves

• Directional control valves start, stop or change the direction of flow in compressed air applications
• Operator is mechanism that causes valve to change state
  
  • Manual, mechanical and electrical
• Monostable
  
  • Spring return, defined preferred position, automatic return, latched signals
• Bistable
  
  • No return position, remains in either position, pulse signals

Actuators

• Part of the system that converts potential energy from compressed air into mechanical motion
• Can be linear or rotary
• Single (spring and open to atmosphere) or Double acting

Other equipment:

• Air filter: removes contaminants
• Air regulator: controls and stabilises air pressure downstream
• Air lubricator: to aid life of components
• Precision regulator: controls and stabilises pressure downstream, but to a much higher tolerance

Question 186

Describe the purpose of a functional specification and list the types of information that should be contained within this documentation.

Answer 186

Document specifying

• the functionality of an automation project
• and agreeing the participation of different parties involved (End-Users and Systems Integrators).

Technical document that:

• Defines the functional scope of the project.
• Provides common understanding between parties.
• Should be unambiguous and testable.
• Forms the basis of contractual agreements
• Referred to as the bible of the project by
  
  • helping to eliminate specification creep
  • and project disagreements.

Types of information found in a functional specification:

• Functionality
• Error handling procedures
• Recovery processes
• Processes requiring manual intervention (Operation Assistance)
• Production rate
• Required uptime
• Number of operators
• Frequency of incoming and outgoing components
• Delivery format of incoming / outgoing components
• Quality of components
• Services required to run the solution (e.g. 120 PSI compressed Air, 240VAC 10Amps)
• Maintenance schedule

Question 187

Outline the reasons for the introduction of structured testing and describe an approach for testing an automation solution.

Answer 187

• Solution testing is an important activity
• Full functionality should be tested.
• Tests should be performed early
  
  • To provide time to remedy any issues that arise

Automation solutions made by

• integrating multiple units of automation together to provide an integrated solution (system).
• Testing process broken into two phases:
  
  • unit testing
  • system testing.
• As individual modules are tested and integrated with each other, system tests can be carried out.
• System tests evolve as the scale of the system is increased.
• Sequenceof integrating modules together and undertaking system testsis critical.
• Functional specification used to develop a plan for unit and system testing.

Unit tests should include:

• Unit Functionality / Performance
• Operational Status (process requiring human intervention)
• Error Conditions
• Interfaces of both Hardware / Software

System tests should include:

• Integrated Functionality / Performance
• Error Handling / Recovery Strategies
• Interfaces of both Hardware / Software

Question 192

What are the key project milestones that should be considered in the development, integration and delivery of a typical automation project? In each case, note which project organisation is responsible for each milestone and note any interdependencies.

Answer 192

Project milestones that should be considered in the development, integration and delivery of a typical automation project:
1 - Idea (Initial Requirement) [End Customer]
2 - Talk to various system providers [End Customer]

3 - Provide a Requirement Specification for Tender [End Customer]
4 - Basic Tests, Submit Functional Specification [Systems Integrator]
5 - Agreed Functional Specification (Performance Requirements) [All Parties] 6 - Prototype key technology components [Systems Integrator]
7 - Design System [Systems Integrator]
8 - Procure Components [Sub Vendors]
9 - Build Production System [Systems Integrator]
10 - Integrate System Components [Systems Integrator]
11 - Factory Acceptance Test (FAT) [All Parties]
12 - Site Acceptance Test (SAT) [All Parties]
13 - Final Performance Test [All Parties]

Question 193

Describe the purpose of a functional specification.

Answer 193

The purpose of a functional specification is to:

• Specify what the automation will achieve.
• It will form the basis of the contract between the automation vendor and the customer, and will form the basis for the acceptance trials.
• It will minimise specification creep.
• Provide a base from which requested changes during the project can be identified and appropriately costed.
• It forms the main means of communication between the customer and the vendor to minimise the chances of disappointment and / or nasty surprises

Question 194

What is to be included in the functional specification?

Answer 194

The main areas to be included in the functional specification:

• What the system has to deliver (not on how this should be achieved).
• Form, quality and method of delivery of incoming materials.
• Form and method of delivery of finished products.

The functional specification will require further iteration with material suppliers and customers. The following additional areas should be covered:

• The context within which the automation will operate, e.g. skill levels of operators, reliability of interfacing equipment outside the control of the vendor.
• Cycle Time.
• Some measure of availability, usually expressed as output over a specified period.
• Form and extent of manual intervention.
• Scheduled periods of operation and maintenance.
• Levels of defects, and what to do when defects are detected.
• Error detection and recovery, recoverable and non-recoverable errors. Form of error logging.

All the statements in the functional spec should be testable and so vague wording should be avoided. For example, “The system should operate reliably” is not acceptable, some measures of reliability should be provided.

Question 195

Describe what is meant by unit tests?

What additional testing needs to be done before the system is ready for site testing and why?

Answer 195

Unit Tests

• Unit tests are carried out on each component (Unit) of a production system.
• Typical components of a production system would be for example a Robot, Part Feeder or Conveyor Docking Station.
• Each component would be tested in isolation to ensure it works correctly and meets performance requirements specified within the functional specification.

Typical Unit tests would include:

• Test that hardware functionality meets performance specifications
• Operational status of hardware is reflected within the unit control system.
• Error conditions are detected and captured correctly.
• Unit control systems interfaces work correctly allowing systems integration to take place.

System tests

• System tests are carried out on groups of production components once individual unit tests have been completed.
• A number of components are integrated together in these tests.
• The number of components is gradually increased as success criteria are meet.
• Typically these tests examine the way production components work with each other both at a hardware and systems level.

Typical System tests would include:

• Test hardware interfaces between production components.
• Ensure correct software hand-shaking between component control system and overall production system.
• Ensure that error recovery strategies for recoverable and non-recoverable errors work correctly.

These tests will go onto include specific production scenarios and provide the ground work for the Factory Acceptance Tests (FAT) and Site Acceptance Tests (SAT)

Question 196

What are the issues with the pharmaceutical industry?

Answer 196

Issues with batch production in pharma

• Batch is very versatile but extremely slow and not very precise.
• There is approximately a 2- year timeframe from the start to the end of the process development (primary manufacturing part only).
• This approach requires capital intensive investment very early in product development to allow the running of clinical studies.
• This same process needs to be able to ramp up to full production.
• Therefore very high cost associated with failure.
• The batch approach is also not very agile to deploy around the world and leads to centralised manufacturing, whereas local production and distributed manufacturing may be important for future cost reduction.
• In batch manufacturing, it is difficult to reconfigure or change the design and this again adds to the cost of the products.

From lectures

• A large % of products in different phases fail, but clinic must be supplied for years and plan for success
• If launched, typically market is supplied for 10 years
• Demand volume is uncertain
• Once patent has expired, product volumes are likely to fall
• Orders must always be fulfilled
• Must manufacture to strict codes

It’s hard to plan

• If product fails, equipment can be reused
• But it is labour intensive and slow in making the product

Question 197

What is the solution to the problems in the pharmaceutical industry?

Answer 197

Try to be agile instead:

• Repurposed or negligible cost or time to change
• Precise
• Fast to supply
• Low labour

3 ideas:

• Modularisation
  
  • System is deconstructed into more independent units (modules)
  • Useful for reducing the complexity of the system
  • Leads to
    
    • Replication, mobility, standardisation means
    • Increased speed in delivery and lower cost
• Digitalisation
  
  • Leads to:
    
    • Faster connected, reduction of downtime due to automation
    • Data for predictive modelling
    • Maintenance, how to do a task, deep learning, automating design
• Process intensificationusing continuous manufacture
  
  • Footprint is smaller for same output
  • Leads to small precise plant
  • Continuous processing is a technology that provides, small precise replicatable production.

One approach

• Substituting a number of the batch steps with a continuous process.
• The approach requires the design of a modular continuous manufacturing plant.
• This building-block approach allows
  
  • reconfiguration, agility to deploy, agility to re-usein other processes if the product fails,
  • benefit of the precision and higher levels of automation achieved in continuous manufacturing and
  • the ability to build closer to the point of distribution rather than have large centralised manufacturing sites.
  • Each module is a unit operation and savings will be realised even by replacing a sequence of a few of the batch steps.

It may be noted that pharmaceutical companies are risk averse about moving the entire process to continuous manufacturing because of the challenge of controlling crystallisation and the significant knowledge currently in place that surrounds batch processing in this field.

Question 198

Give some facts oil and gas in the UK

Answer 198

• Oil and gas provides more than 75% of UK’s total primary energy
• By 2035 will still be 66%
• Electricity, transportation and heating account for roughly one third of the UK’s primary energy demand, with oil for transport and gas for heating dominating these markets.
• Natural gas is the cleanest of all fossil fuels, burning nearly twice as efficiency as coal and producing much less CO2 per unit of energy

Question 199

What are the different production fluids (oil, gas, etc.)?

Answer 199

Different production fluids

• Crude oil is a mixture of 200 or more organic compounds, mostly hydrocarbons. Graded according to API number (higher API = lighter, thinner crude)
• Natural gas as used by consumers is almost entirely methane. Wellhead gas requires significant additional processing to meet transportation pipeline specifications.
• Condensates or natural gas liquids associated with natural gas are a valuable by product. They are widely used as raw materials for oil refineries and petrochemical plants.

Question 200

Describe the process of oil production from wellhead to to export?

Answer 200

Production facilities can vary from onshore wells to offshore floating wells.

Process from production wellheads to export:

• Production well head
• Production separators:
  
  • Separate water, crude oil and natural gas
• Gas
  
  • Compressed
  • Gas meter
  • Pig launcher
  • Gas pipeline
• Oil
  
  • Storage
  • Crude pump
  • Oil meter
  • Pig launcher
  • Oil pipeline

Question 201

Describe the production well head

Answer 201

Production well head

• Assembly of valves, spools, pressure gauges and chokes to control production
• Sits on top of the oil/gas well, leading down to the reservoir
• Dry completions are either onshore or on the deck of an offshore structure
• Wet completions are subsea, below the surface

Question 202

Describe production separators

Answer 202

Production separators:

• Most wells give a combination of gas, oil and water that must be separated
• Gravity separation: well flow is fed into a horizontal vessel
• Residence time is typically 5 minutes, allowing the gas to bubble out, water to settle at bottom and oil to be taken out in the middle
• Pressure is often reduced in several stages (high pressure separator, low pressure separator etc.)
• Horizontal separators:
  
  • large liquid handling capacity
  • Sufficient time for settle out of liquid droplets from the gas
• Vertical separators (scrubbers)
  
  • High gas volumes
  • Small footprint area

Question 203

Describe gas compression

Answer 203

Compression

• Gas from separators has lost so much pressure that it must be recompressed to be transported
• Turbine compressors gain energy by using a small proportion of natural gas that they compress
• Turbine operates a centrifugal compressor, which contains a type of fan that compresses and pumps the natural gas
• Compression system includes a large “train” of associated equipment such as scrubbers (removing liquid droplets) and heat exchanges, lube oil treatment etc.

Question 205

What are oil terminals and their functions?

What are gas terminals and their functions?

Answer 205

Oil: processed onshore rather than offshore as it is easier.

Oil terminals are intermediate oil gathering and distribution stations between offshore oil production locations and onshore oil processing facilities (refineries).

Basic functions:

• Reception of crude oil
• Stabilisation of crude oil (dehydration/desalting, gas/water treatment)
• Fractionation of associated gas into propane and butane
• Storage of stabilised crude, LPG
• Export/ shipment of products into tankers for distribution to refineries

Gas terminals:

• Function of the terminal is to process the raw gas to provide sales quality gas and liquid hydrocarbon by products.
• Gas arrives onshore at around 3 degrees.
• Internal cleaning and inspection of the pipeline is done with pigs (dirt/debris/wax/scale removed)
• Inlet gas receiver catches slugs of liquid from the pipeline

Question 206

What is the detailed process from wellhead to production of oil and gas

Answer 206

Process from production wellheads to export:

Production well head

• Assembly of valves, spools, pressure gauges and chokes to control production
• Sits on top of the oil/gas well, leading down to the reservoir
• Dry completions are either onshore or on the deck of an offshore structure
• Wet completions are subsea, below the surface

Production separators:

• Most wells give a combination of gas, oil and water that must be separated
• Gravity separation: well flow is fed into a horizontal vessel
• Residence time is typically 5 minutes, allowing the gas to bubble out, water to settle at bottom and oil to be taken out in the middle
• Pressure is often reduced in several stages (high pressure separator, low pressure separator etc.)
• Horizontal separators:
  
  • large liquid handling capacity
  • Sufficient time for settle out of liquid droplets from the gas
• Vertical separators (scrubbers)
  
  • High gas volumes
  • Small footprint area

Gas Compression

• Gas from separators has lost so much pressure that it must be recompressed to be transported
• Turbine compressors gain energy by using a small proportion of natural gas that they compress
• Turbine operates a centrifugal compressor, which contains a type of fan that compresses and pumps the natural gas
• Compression system includes a large “train” of associated equipment such as scrubbers (removing liquid droplets) and heat exchanges, lube oil treatment etc.

Heat exchanger needed after to remove heat

• Shell and tube heat exchangers
  
  • Consists of a bundle of tubes enclosed in a cylindrical shell. The ends of the tubes are fitted into tube sheets, which separate the shell side and tube side fluids. Baffles provided to direct the fluid flow and support tubes.
  • Can be heavy and space consuming
  • Suitable for high pressure operation
  • Robust designs with long operational history
• Plate heat exchangers
  
  • Series of corrugated, pressed metal plates clamped together
  • Offshore the use of plate heat exchanges has become universal due to compact size and low weight.
  • Oil cooling prior to storage or pipeline export and some low-pressure gas duties.
• Printed circuit heat exchangers
  
  • Constructed from flat metal plates with chemically milled fluid flow channels.
  • High heat transfer surface densities
  • Suitable for high pressure applications and wide temp range
  • Compact design leading to substantial weight and space savings
  • Low maintenance due to corrosion resistant materials and all welded construction

Gas meter

Pig launcher

Gas pipeline

Oil: processed onshore rather than offshore. Onshore processing plants called terminals.

Storage

Crude pump

Oil meter

Pig launcher

Oil pipeline

Question 207

How is a superconducting magnet made?

Answer 207

How to make a superconducting magnet

Wind coils

• 20-50 km wire per magnet
• Wire costs approx. $1/m
• Coil diameters between 1.5-2m
• Coil weights 20-980 kg

Pot coils in epoxy resin

Assemble coils

Check homogeneity at RT

Joint magnet (joints must have resistance <10^-11 ohms@ 4K)

• Pair up leads to cancel forces
• Dissolve copper matrix with conc. Acid

Fit magnet to cryostat (heat transfer to be <1W)

Pressure test cryostat

Chill magnet to 4K using 3,000-5,000 litres of liquid He

Run magnet to field (460-700A DC @10V)

Test magnet and cryostat

Ship magnet (if shipped cold ‘time to dry’ is 20-28 days)

Question 210

Explain the puttick grid? Explain the different aspects the puttick grid drives?

Answer 210

Puttick grid

The way a product is manufactured should be governed by:

• Production volume and market uncertainty
• Intrinsic product complexity (including variety)

These aspects drive all relevant parameters:

• Product design & material choice
• Production methods, tooling and equipment choice
• Degree of automation
• Degree of integration
• Location, logistics and distribution
• Assembly configuration choices
• People and organisation
• Production control systems

Question 211

What are the factors influencing the type of and extent of automation

Answer 211

• Product volume and variety
• Expected product life span
• Market uncertainty
• Process novelty
• Component/task variability
• Precision, cleanliness, quality, regulatory etc.
• Component complexity

Question 212

What are the different assembly system configurations?

Answer 212

What are the different assembly system configurations?

• Manual: people do the job
• Mechanised: machines help people do the job
• Hard automated: machines do job (same every time)
  
  • Turntable
    
    • Indexing: where different elements of production are at different rotation locations
    • Constant velocity: bottle production
  • Track
    
    • Pallet based. Asynchronous
    • Indexing/synchronous: cars production
• Flexibly automated: robots and other software driven machines do job (can be different)
  
  • Based on off the shelf robots: SCARA, anthropomorphic, cartesian, delta etc.
  • Custom multiaxis

Question 213

What are the examples of the necessary supporting processes and infrastructures?

How much software does an automation system need?

Answer 213

What are the examples of the necessary supporting processes and infrastructures?

• Packaging and feeding
  
  • Order retained: bandoliers, tubes
  • Order re-gained: bowl feeders, centrifugal feeds
• Sensory systems: proximity imaging, gauging
• Actuators: pneumatic, hydraulic, servo electric, solenoid
• Conveyors, turntables, x-y tables
• Proprietary operating systems and programming languages
• Message: exploit what’s out there and don’t reinvent the wheel

Question 214

Why is injection moulding used for manufacturing?

Answer 214

Leading process for manufacturing of plastic products: high volume, identical product

Cost:

• High tooling cost depending on complexity and number of cavities
• Low unit cost

Typical application

• Automotive
• Consumer electronics
• Appliances
• Industrial products
• Household products

Suitability:

• High volume mass production

Quality

• Very high surface finish
• High repeatable process

Related processes

• Reaction injection moulding
• Thermoforming
• Vacuum casting

Speed

• Cycles between 30 and 60 secs

Question 215

How does an injection moulding machine work?

Answer 215

How does an injection moulding machine look and work?

• Clamping
• Injection
• Cooling
• Ejection
• Plastic granules loaded into hopper
• The screw within a heated barrel forcing the polymer towards the nozzle.
• The clamping of the mould cavity and the mould.
• The injection of the molten polymer (details about runners and shot)
• The cooling of the mould
• The ejection of the component (ejection pins)
• The final removal of the sprue
• Recycling of waste back into the process

Question 217

What are the important specs for injection moulding?

Answer 217

What are the important specs for injection moulding?

• Clamping force
  
  • Keep as low as possible: reduce wear and tear without generating flash
• Injection pressure
  
  • Mould internal pressure curve
    
    • First speed of filling must be adequate
    • Switch over to holding pressure
    • No residual pressure when mould is opened
• Shot size: volume of the part plus runners and gates
• Closing force: needed to hold mould for packing and cooling
  
  • Number of cavities x projected parting line part surface x mould cavity pressure

Question 218

Give a closing force example for injection moulding (see picture)

Answer 218

Question 219

What are the other techniques for injection moulding?

Answer 219

What are the other techniques for injection moulding?

Gas assisted injection moulding

• Shut off valve closes to prevent plastic material seeping back into injection head. Gas is injected into the core of the plastic, which is still molten. The gas progresses the molten plastic into the extremities of the cavity

Multi shot

Blow moulding

Question 220

Give some advanced applications of polymers

Answer 220

Advanced applications of polymers:

Self-healing

Drug delivery

• Release from surface
• Diffuse from swollen network
• Release due to erosion
• Efficiency depends on chemical structure and porosity of particle

Organic solar cells

LEDs

• Holes injected into conductive layer, electrons injected in emissive layer, recombine at interface emitting light

Question 221

Describe the different types of heat exchangers

Answer 221

Heat exchanger needed after to remove heatShell and tube heat exchangers

• Consists of a bundle of tubes enclosed in a cylindrical shell. The ends of the tubes are fitted into tube sheets, which separate the shell side and tube side fluids. Baffles provided to direct the fluid flow and support tubes.
• Can be heavy and space consuming
• Suitable for high pressure operation
• Robust designs with long operational history

Plate heat exchangers

• Series of corrugated, pressed metal plates clamped together
• Offshore the use of plate heat exchanges has become universal due to compact size and low weight.
• Oil cooling prior to storage or pipeline export and some low-pressure gas duties.

Printed circuit heat exchangers

• Constructed from flat metal plates with chemically milled fluid flow channels.
• High heat transfer surface densities
• Suitable for high pressure applications and wide temp range
• Compact design leading to substantial weight and space savings
• Low maintenance due to corrosion resistant materials and all welded construction

Air cooled heat exchangers

• Where cooling water is too costly.
• Multiple calculations are required to produce an optimum design considering air flow rate, tube design, fin types etc.

Question 222

What properties depend on molecular weight?

What are the different measures for molecular weight?

Answer 222

What properties depend on molecular weight?

• Modulus
• Strength
• Viscosity
• Melting temperature
• Glass transition temperature

Question 223

What is gel permeation chromotography

Answer 223

Gel permeation chromatography

• Type of size exclusion chromatography
• Measures molecular weight distribution and structure
• Separates based on the hydrodynamic volume of the polymer
• Higher MW, higher hydrodynamic volume
• Pores exclude large molecules, so they move faster through the column

Factors affecting GPC spectrum:

• Sample interaction with column
• Temperature
• Flow rate
• Gel permeation chromatography is a separation technique.
• The columns contained insoluble beads with a rigid pore structure.
• The pores can exclude very large molecules, allow partial permeation of medium sized polymers and allow total permeation of smaller molecules.
• The larger molecules therefore don’t have a long residence time in the column and flow through.
• This means the polymers are separated with the largest coming out first and smallest last.
• The full molecular weight distribution can be defined and compared with previous results to see if this is influencing the mechanical behaviour.

Question 224

What is differential scanning calorimetry?

Answer 224

Differential scanning calorimetry

• Thermal energy of a sample is monitored as a function of temperature
• Measures thermal energy of phase transitions (crystallisation, melting point, Tg)
• Heat capacity increases above Tg
• Heat released on crystallisation and absorbed on melting
• The amount of energy needed to increase the temperature of a sample is measured.
• This detects phase transitions because of the quantity of energy needed to change temperature.
• The glass transition temperature can also be observed.
• Also, the percentage crystallinity can be defined.

Question 225

What is thermogravimetric analysis?

Answer 225

Thermogravimetric analysis

• Measure thermal stability of a sample
• Mass of a sample is measured as a function of temperature
• Can identify material composition and presence of contaminants
• Characteristics different in inert or oxidising environment
• Derivative curve highlights different mass loss events
• Percentage weight loss can be used to calculate composition
• This thermal technique measures the rate of change in mass as a function of temperature.
• This can identify changes in the oxidative stability and the composition.
• This is a highly sensitive technique and any contamination would be immediately highlighted.
• This technique is often used to identify the percentage of filler in a polymer sample, which also effects the mechanical properties.

Question 226

What is UV spectroscopy?

Answer 226

UV spectroscopy

• Can identify material composition and presence of contaminants
• Measures absorbance of UV by the sample
• Can be used to identify chromophores
• Absorbance proportional to concentration

Question 227

What is fourier transform infrared spectroscopy

Answer 227

Fourier transform infrared spectroscopy

• Can identify material composition and presence of contaminants
• Measures vibration and stretching of chemical bonds
• Used to examine structure and presence of functional groups
• Samples can be solid, liquid or gas

Question 231

What are the common failure modes for superconducting magnets?

Answer 231

Quench:

• wire stops superconducting, becomes resistive and 1000 litres of liquid He suddenly boil away

Electrical short

Homogeneity

• Lack of either intrinsic or induced by site factors

Decay

• Full field not maintained between service intervals – maximum loss allowed is 0.1ppm/hr

Boil off problems

• Cryostat performance poor – system will require frequent topping up of liquid helium
  
  • Poor vacuum (leak)
  • Thermal short
  • Poor connection to refrigeration

Question 232

What are the safety hazards in superconducting magnets?

What are the new trends in superconducting magnets?

Answer 232

What are the safety hazards:

• Strong magnetic fields
• Extreme cold
• Large heavy magnets
• Strong acids – HF and HNO3

What are the new trends:

• Minimum He system/ ‘dry’ system
• Higher fields
• Warm superconductors
• Cheaper systems: suitable for unsophisticated/low tech environments

Question 233

What is an LCA, explain it for biopolymers

Answer 233

LCA

• Standardised framework for determining the environmental impact of product or process, to allow comparisons to be made
• But interpretation varies and users can select different options
• Should cover entire life cycle of product, but many studies don’t do this

Difficulties with biopolymers:

What should be included within agriculture:

• Soil carbon/nitrogen dynamics
• Nitrogen emissions from composting
• Manufacturing environment, maintenance of equipment

Location specific:

• Transport requirements
• Incineration efficiencies
• Farming practices
• Energy production is country specific
• Electricity has different impacts depending on how it is generated

Disposal often ignored

Studies look at limited impact factors

Impact categories include:

• Contribution to climate change
• Resource depletion
• Ozone depletion
• Energy and water use
• Acidification
• Eutrophication: increased nutrients in water systems resulting in excessive bland growth
• Toxicity

Can’t be combined: impacts are assessed separately

Question 235

What is a laser? What are the different laser media?

Answer 235

What is a laser?

• Laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation
• Laser means: light amplification by stimulated emission of radiation

Stimulated photos have same:

Direction, polarisation, phase, wavelength

Laser resonator formed with mirrors either side of gain medium

Question 236

What are the different laser mediums?

Answer 236

Different laser media:

• Gas: electrical discharge
• Solid state: optical excitation
• Semiconductor: electrical current
• Dye: optical excitation

Common properties:

• Directionality
• Brightness
• Monochromatic (narrow band of wavelengths)
• Spatial coherence (better focusability)

Question 237

What are the different solid state laser geometries?

What does a fibre look like?

Answer 237

What are the different solid state laser geometries?

Rod

Slab

Thin disk

Cladding pumped fibres

What does a fibre look like?

Question 238

What is the different between a fibre laser and a solid state laser?

Answer 238

Question 240

What are the different applications for fibre lasers?

Answer 240

What are the different applications for fibre lasers?

Material processing

• Welding
  
  • Accurate and consistent processing: fast, flexible and high strength
  • Low levels of thermal distortion
  • Able to weld difficult applications
• 3d printing
  
  • High levels of beam stability: stable and well controlled
  • Process a variety of powders
  • Ideal for AM: Inherent back reflection protection
• Cutting
  
  • Highly productive: match leading cutting speeds
  • High accuracy and repeatability: intelligent software and stability
  • Large range of materials and thicknesses
  • Energy efficient
• Ablation and cleaning
  
  • No solvents/chemicals
  • High quality, minimal heating, non contact
• Drilling
  
  • Small feature size, high aspect ratios, various materials
• Micromachining
• Marking/engraving
  
  • Permanent
  • Non-contact: no wear
  • Versatile application
  • High speed, high precision

Sensing

• Vibration measurement
• Oil and gas exploration
• Remote gas sensing
• Terrestrial mapping
• Wind sensing

Healthcare

• Vision correction
• Kidney stone ablation
• Skin rejuvenation
• Soft tissue ablation
• Dentistry

Other

• Cinema projection
• Communications
• Directed energy weapons

Applications:

• Automotive: cutting, marking, welding
• Batteries: welding, drilling, engraving, marking
• Medical: welding, cutting
• Advanced manufacturing: micromachining
• Solar: cutting, marking, welding
• Aerospace: drilling, welding, cutting, marking
• Dental: engraving and marking

Question 241

What are the important details for diamond turning?How is it used in IR lens production?

How are UV lens made?

Answer 241

Diamond turning

• Zero or slightly positive rake angle for soft materials
• Negative for IR materials
• Highest cutting speed that can be permitting whilst providing good dynamic stability
• Vacuum extraction of swarf to prevent scratching
• Flood oil or spray mist coolant on metals
• Hard brittle materials control the feed rate
• Depth of cut is less sensitive for hard materials

IR optics:

• Saw
• Rough grind
• Diamond turning
• Clean
• Coating

UV optics:

• Saw
• Lap
• Rough grind
• Fine grind
• Clean
• Ion beam figuring
• Cleaning
• Coating

Question 242

Name the factors influencing workpiece accuracy and production capability

Answer 242

Factors influencing workpiece accuracy and production capability

Environment related

• Temp variation
• Vibrations
  
  • Seismic
  • Through pipes
  • Air borne (noise)
  • Electric noise

Workpiece related

• Stiffness variation
• Thermal distortion
• Clamping distortion
• Residual stresses
• Heat response

Process related

• Tool geometry
• Tool wear
• Tool mounting (dynamic stiffness)
• Process variations with tool wear
  
  • Specific energy variations
  • Cutting force variations
  • Removal mode
• Coolant variations

Machine tool related

• Motional accuracy
• Deflection (stiffness)
• Thermal distortion
• Dynamic resonance’s
• Accuracy/ resolution of measuring systems

Question 243

Describe the chip manufacturing process

Answer 243

Chip manufacturing process

• Silicon ingot sliced into blank wafers
• 20 to 30 processing steps later it is a
• Patterned wafer
• This is diced into individual dies
• This is tested and bonded to package
• This packaged die is then tested and shipped to customers

Question 244

Describe microprocessors patterning process

Answer 244

Patterning process

• Prepare wafer
• Apply a photoresist
• Align a photomask (Cr and glass)
• Expose to UV light
• Develop and remove photoresist exposed to UV light
• Etch the exposed oxide
• Remove remaining photoresist

Question 245

What are the three technologies that determine the performance of semiconductor lithography systems?

Answer 245

What are the three technologies that determine the performance of semiconductor lithography systems

1. Resolution capability of the projection lens: for forming extremely intricate electronic circuit patterns
   * Consists of more than 20 lenses, some over 1m long
2. Alignment accuracy: ensuring that the next pattern is accurately aligned to the base pattern
   * When electronic circuit patterns are repeatedly formed on a silicon wafer many times, they must be positioned with accuracy to the nanometre
3. Throughput: indicates the processing efficiency of a semiconductor lithography system
   * Productivity during IC mass production is improved when high speed movements of the wafer stage and other processes increase throughput

Question 246

Why is feature size important? What is the limitation to feature size?

Answer 246

Why is feature size important? What is the limitation to feature size?

• Progress in semiconductor manufacturing is all about reducing the size of the features that make up integrated circuit (IC) designs.
• Smaller features allow for faster and more advanced ICs that consume less power and can be produced at lower cost.
• Resolution limited by wavelength, currently extreme ultra violet is used

Question 247

What are the other options for silicon chips?

Answer 247

What are the other options for silicon chips?

Quartz mask in contact with silicon

Mask pressed into molten layer of silico

Question 248

How does roll to roll printing work?

Answer 248

How does roll to roll printing work?

• Raw materials
• Deposition
• Patterning
• Packaging
• Finished product

Examples include:

• OLED lighting
• Solar cells
• Flexible display
• Flexible battery
• Flexible RFID

Question 249

What are the automation challenges of roll to roll printing?

Answer 249

What are the automation challenges of roll to roll printing?

• Register control: position match
• Tension control
• Synchronisation
• Positioning
• Cam calculation
• Winder
• Cross communication
• Motion control
• Virtual master

Question 251

Describe nanoscribe

Answer 251

Nanoscribe:

• Laser beam sent through an inverted micro scope onto a piezoelectric 3D scanning stage
• Laser beam fired through lens to hardens material (light photoresist).
• Material hardens through polymerisation
• This process employs two photon photolytic techniques and high resolution positioning.
• The laser beam itself has a computer-controlled beam guidance system that translates a 3D CAD model directly into 3D structures of almost any complexity at any scale.
• Essentially it can fabricate microstructures as small as 500 nm, including those with complex geometries and support structures, at extremely high resolutions (100nm with reports of new materials reaching 45nm).
• The 3D printing technology that Nanoscribe developed has allowed sub-micron parts to be fabricated with geometries and internal structures that would be completely impossible to create using standard micro-scale manufacturing techniques.

Question 252

Describe fountain pen lithography

Answer 252

Fountain pen nanolithography

• Deposit a nanoparticle dispersion of material
• FPN is a printing method, which, utilises a reservoir filled with nanoparticulate ink.
• These ink solutions can undergo nanochemical changes during the lithography process, resulting in the desired functional lines and structures.
• Line width control from 15 nm to over 1000 nm have been demonstrated.
• Line produced showed micrometer lengths, consistency of line dimensions, precise placement, and conductivity.
• Similar to the reservoir in fountain pens, the nanopipette reservoir enables numerous lines to be printed without refilling.
• This technology could be expanded to the production of conductors and actuators, correction of flat panel displays, and mask repair applications.

Question 253

Describe ion beam machining

Answer 253

Ion beam machining

• Ion source fired through imaging gas
• This is then focused through apertures and scanning deflectors
• Before being fired through the final lens at the workpiece
• Size of feature determined by size of ion:
  
  • Gallium (largest)
  • Neon
  • Helium (smallest, 0.5nm)

Question 254

How is core of composites manufactured?

Answer 254

Manufacture of core such as honeycomb

Tends to be batch production

• Labour intensive
• Aluminium: print wheel adds adhesive to aluminium foil
  
  • Strips are cut and stuck together
  • Heated under pressure
  • Cut and expanded
• Nomex: print wheel similar
  
  • Cut and stuck together
  • Heated under pressure
  • Expanded and heat set
  • Dip in phenolic resin and cured at 150 degrees

Question 255

How is carbon fibre manufactured?

Answer 255

How is carbon fibre manufactured?

• Bulk chemical: AN
• Batch is then polymerised: PAN
• Dope (high energy required in solvent recovery process)
• Fibres are then spun
• Fibres are washed and stretched: PAN precursor fibre
• Oxidise and carbonise: slow process
• Surface treatment and sizing

Question 257

How is prepreg manufactured?

Answer 257

How is prepreg manufactured?

Solvent impregnation process:

• Carbon fibres sheets rolled out.
• Accumulator at either ends to tension the fibre and to allow the process to run continuously between rolls.
• Sheets go through solvent to add resin
• Sheets travel up column and undergo solvent management
• Inspection Light - to test if light can go through (pass or fail test)
• Compaction rollers
• Total weight inspection
• Protective poly at the end to separate fibres.

Prepreg impregnation process:

• Resin is pressed onto paper using a film weight check
• In separate process carbon fibres are rolled out
• As this happens paper covered in resin is pressed each side of the fibres
• It is heated in a heat table
• It is then cooled and paper is removed leaving the resin on the fibres
• Light table used to measure consistency of fibres
• Then protective poly is rolled on

High volume, low cost process

Residual solvent is a problem

Negative environmental impact

Question 258

What are the different manufacturing methods with prepreg?

Answer 258

Manufacturing with prepreg

• Hand Lay Up - High waste, low investment, high labour
• Automated Tape Lay Up - Medium waste, moderate investment, lower labour
• Automated Fibre Placement - low waste, high investment, little labour

Question 259

What are the alternative methods for manufacturing composites?

Answer 259

What are the alternative methods for manufacturing composites?

• Compression moulding: fibres are chopped and compressed with compacting rollers and resin
• Infusion: fibres are laid in part and resin is injected under a vacuum throughout the part
• Thermoplastic prepreg

Question 260

What are the new trends in fibre growth?

Answer 260

What are the new trends in fibre growth?

Wider:

• Bigger, stiffer roller sets, more powerful motors
• Demand for single product to avoid cost of changes
• No defects in production or delays = QUALITY

Faster:

• Same time in process therefore longer equipment
• New chemistry: faster reactions therefore shorter process time

Heavier

• Thicker filaments currently have poorer properties as they are less uniform
• More filaments per tow: properties affected by oxygen diffusion into bundle

Question 263

What factors are considered when selecting an adhesive?

Answer 263

What factors are considered when selecting an adhesive?

Substrates to bond

Cure speed, pot life, gap filling, colour

Chemical resistance, temperature resistance

Specific approvals

Question 264

What are the different joint loading conditions?

Answer 264

What are the different joint loading conditions?

• Tension
• Compression
• Shear
• Cleavage
• Peel

Question 265

Give examples of potential defects that can occur in injection moulded parts.

Which of these issues can CAD solve?

Answer 265

Give examples of potential defects that can occur in injection moulded parts

• Short shot
• Humidity
  
  • Drying used pre process
• Contamination by other coloured granules
• Sink marks or Voids:
  
  • Depressions on one side of a component due to the thicker section or a large feature on the other side. These thicker areas shrink upon cooling to give the depression. The cooling time needs to be sufficient to allow cooling in the mould.
• Knit lines and Weld lines:
  
  • This appears as a discoloured line, where molten plastics meet as they flow from different parts of the mould. The flow fronts do not bond correctly, most often due to partial solidification.
• Warping
  
  • A deformation or bending where there is uneven shrinkage across the component. This is usually due to uneven cooling across the material. Different cooling rates or rapid cooling leads to internal stresses.
• Flash
  
  • If the clamp force is not sufficient, the mould/die are not precisely manufactured, the mould/die are worn or corroded or if the injection pressure is too high, there will be a leak of the polymer around the join leading to flashing.

Which of these issues can CAD solve?

CAD based analysis:

• Warp analysis: used to predict shrinkage as a result of stress on the mould
• Cooling analysis: checks for uniform cooling throughout the mould. Potentially reducing cooling time

Question 266

What are the different AM methods?

Answer 266

What are the different AM methods?

• VAT photo polymerisation (StereoLithogrAphy): material is cured by light activated polymerisation
  
  • Continuous liquid interphase production: continuous elevation, liquid resign, o2 permeable window
  • Advantages: good resolution, surface finish and rapid
  • Disadvantages: limited materials, messy, support removal
• Material jetting: droplets of build material are jetted to form an object
  
  • UV lamp and inkjet heads and levelling roller
• Binder jetting: liquid bonding agent is jetted to join powder materials
• Material extrusion (Fused Filament Fabrication): material is selectively dispensed through a nozzle and solidifies
  
  • Advantages: widest range of materials, widest range of processing conditions, multi material, dedicated support material
  • Disadvantages: surface finish, toolpath planning, slow rate
• Sheet lamination (LOM): sheets are bonded to form an object
• Powder bed fusion (Selective Laser Sintering/SLM): energy (typically a laser or electron beam) is used to selectively fuse regions of a powder bed
  
  • Mount platform, heat bed, perform cycle, cool, remove platform, post process (CNC, surface finish, anneal etc)
  • Advantages: can print metals, rapid, good surface finish, wide variety of materials
  • Disadvantages: powder handling, high energy, post processing
• Directed energy deposition (LENS): focused thermal energy is used to fuse materials by melting as deposition occurs
  
  • Powder fired into a laser beam

Question 267

Why is AM increasingly widespread now?

Answer 267

Why is AM increasingly widespread now?

• Rapid prototyping
• Reducing assembly
• Complex geometries
• Multi material
• Enhanced performance
• Low volume manufacturing
• Supply chain efficiency (low inventory)
• Reduced material consumption

Question 268

Explain vat photo polymerisation

Answer 268

VAT photo polymerisation (StereoLithogrAphy):material is cured by light activated polymerisation

• Continuous liquid interphase production: continuous elevation, liquid resign, o2 permeable window
• Advantages: good resolution, surface finish and rapid
• Disadvantages: limited materials, messy, support removal

Question 269

Explain material extrusion and its ads and disads

Answer 269

Material extrusion (Fused Filament Fabrication): material is selectively dispensed through a nozzle and solidifies

• Advantages: widest range of materials, widest range of processing conditions, multi material, dedicated support material
• Disadvantages: surface finish, toolpath planning, slow rate

Question 270

Explain powder bed fusion and advantages

Answer 270

Powder bed fusion (Selective Laser Sintering/SLM): energy (typically a laser or electron beam) is used to selectively fuse regions of a powder bed

• Mount platform, heat bed, perform cycle, cool, remove platform, post process (CNC, surface finish, anneal etc)
• Advantages: can print metals, rapid, good surface finish, wide variety of materials
• Disadvantages: powder handling, high energy, post processing

Question 271

Explain material jetting, sheet lamination, directed energy deposition

Answer 271

• Material jetting: droplets of build material are jetted to form an object
  
  • UV lamp and inkjet heads and levelling roller
• Sheet lamination (LOM): sheets are bonded to form an object
• Directed energy deposition (LENS): focused thermal energy is used to fuse materials by melting as deposition occurs
  • Powder fired into a laser beam

Question 274

How are ceramics made?

Answer 274

How are ceramics made?

Material prep: chemical, physical, morphological

• Weigh materials, milling, add binder, spray dry, characterise powder

Forming: process options, dimensional and density control

• Dry powder: isostatic press, roll compaction, hot press
• Casting: tape cast, slip cast, pressure cast
• Plastic forming: extrusion, injection mould
• Chemical vapor deposition

Firing: kiln options, temp & time, refractory, atmosphere

• Continuous, batch, atmosphere, vacuum, HIP, hot press

Finishing: shape & tolerance, finish, features, assembly

• Shaping: CNC grinding, laser machining, cutting
• Surface treatment: metallizing, plating and glazing, coating
• Assembly: brazing, solder, adhesive
• Specialised: cleanroom assembly, inspection and test, materials R&D

Question 275

Why use ceramics?

Answer 275

Why use ceramics?

Mechanical

• Hardness
• Rigidity
• Toughness
• Wear

Chemical

• Corrosion
• Biocompatible
• Ultra-pure
• Inert (or active)

Thermal

• Shock & stability
• Conductivity
• Expansion
• Creep

Electrical

• Resistivity
• Conductivity
• ESD – safe
• Dielectric strength

Question 278

What is hydrodynamic volume?

Answer 278

What is hydrodynamic volume?

It is an indication of the expansion factor alpha

High alpha means it is a good solvent

Solvent polymer interactions are higher than polymer polymer interactions

Question 285

What are the different techniques for classifying polymers?

Answer 285

• Gel permeation chromatography (GPC) – MW distribution
• Differential scanning calorimetry (DSC) – Thermal transitions
• Thermogravimetric analysis (TGA) – Thermal stability
• Ultraviolet-visible spectroscopy (UV/vis) – structure/composition
• Fourier transform Infrared spectroscopy (FTIR) – structure/composition

Question 286

Define bio based polymers and drop in bio based polymers

Answer 286

Bio based polymers:

• Polymer produced from renewable natural resources e.g. PLA, PHA

Drop in bio-based polymers:

• Chemically identical to conventionally sourced polymers, but are (at least partially) produced from biomass e.g. PET, PE from ethanol feedstocks (sugar cane)

Polymers may be biodegradable: their properties deteriorate and may completely degrade under aerobic or anaerobic conditions

• Bio based may or may not be biodegradable.
• Tend to be starch based derived from potatoes or wood
• Or protein based for biomedical applications

Term bio polymers sometimes used to describe bio-compatible polymers suitable for biomedical applications

• E.g. silicone rubber, polyethylene, PMMA

Currently 2% of world production is bio-based polymers. However, it is increasing fast estimated 20% per year. Attention is focussing on a few polymers, particularly those showing potential for scale up and packaging.

Question 287

What are the properties and applications of

Starch

PLA

PHA

Answer 287

What are the properties and applications of

Starch

• Blended with other polymers to make materials with range of properties
• Lower starch content associated with improved properties but decreased biodegradation
• Substitute for PE, PP and EPS
• Food and agricultural applications: bags, packaging

PLA

• Physical properties similar to PS
• Can be modified to resemble PE and PP
• Grease resistance comparable to PET
• Degrades by hydrolysis
• Food and medical applications: plastic plates and knives and forks

PHA

• Comparable to PP
• Can also substitute for PE and PVC
• Degrades in composting and anaerobic conditions
• Razors, toothbrushes, bags etc.

Question 288

What is the production process of

• Starch
• PLA
• PHA

Answer 288

Production process of

• Starch:
  
  • Wet milling of corn
  • Extrusion into TPS
  • Add water and plasticiser
  • Reactive blending into starch blend
  • Add PVA and PCL
• PLA
  
  • Wet milling of corn into glucose
  • Fermentation into lactic acid
  • Polymerisation into PLA
• PHA
  
  • Wet milling corn into glucose
  • Fermentation and extraction into PHA

Question 289

What are the issues with biopolymers?

Answer 289

Issues with biopolymers:

• Intensive agriculture
  
  • Large scale monocultures
  • Agrochemical use
  • Irrigation
• Capacity, competition with food production
  
  • Biopolymers cannot meet demand in near future
• Energy requirements
  
  • Fossil fuels used for: synthetic fertilisers, pesticides, farm machines, lights, pumps, fans, heating, water
• Cost
  
  • More expensive than conventional polymers
• Disposal
  
  • Mechanical recycling
    
    • Bio polymers contaminate conventional recycling
  • Composting: home/industrial degrades into CO2 and water.
    
    • Biopolymers not always suitable for home composting
    • May not degrade in industrial composters or at all
  • Feedstock or chemical recycling
  • Energy recovery
  • Landfill
    
    • Bio polymers will generate methane if degradable in landfill
• Performance

Question 291

What are the future improvements for biopolymers?

Answer 291

Future improvements:

• Integrated system agriculture
• More use of renewable
• Alternative feedstocks
  
  • Crop waste is used but energy requirements tend to be higher
  • Consumer food waste: problems of contamination can be lower energy requirements
• Improved farming practices
  
  • Reduction in agrochemicals
  • Reduction in fuel costs
• Optimisation of polymer production processes

Question 296

What are the advantages of fibre lasers?

Answer 296

What are the advantages of fibre lasers?

• Excellent heat management
  
  • High efficiency: low heat dissipation
  • High surface area/volume: helps heat removal
• High mode quality
  
  • Highly directional and coherent output
• Compact and robust
• No re-alignment
• Telecom leveraged

Question 307

Which properties change with size?

Why do properties change?

Answer 307

How does size affect properties?

• Nanosized particles exhibit different properties than larger particles

Properties: describe how the material acts under certain conditions

Properties that often changes:

• Optical: colour, transparency
• Electrical: conductivity
• Physical: hardness, boiling point
• Chemical: reactivity, reaction rates

Why do properties change?

Four reasons:

• Gravitational forces become negligible and electromagnetic forces dominate
  
  • Gravity is a function of mass
  • Electromagnetic are not affected by mass
  • Electromagnetic forces are 10^36 times stronger than gravity
• Quantum mechanics is used to describe motion and energy instead of classical mechanics
• Greater surface to volume ratios
  
  • Greater amount of substance comes into contact with surrounding material
  • Better catalysts
• Random molecular motion becomes more important

It is important to understand these factors when researching new materials and ways to manufacture goods from them

Question 313

What is prepreg? What are the advantages and disadvantages?

Answer 313

What is prepreg? What are the advantages and disadvantages?

Prepreg: resign pre-impregnated reinforcement, typically thermoset epoxy UD tape for cure in autoclave, automatically laid up for aerospace applications

Advantages

Resin levels accurately set by supplier

Uni directional (UD) fibre is aligned to structural loads

Allows for complex lay ups in automated processes

Cana use high viscosity matrices for high toughness and damage tolerance

Disadvantages

Higher material cost from multi-step process and cold supply chain

Needs expensive tooling capable of withstanding high temps and pressures

Debulking need on thicker laminates

Question 318

What are the important parameters for successful bonding?

Why is viscosity important?

What is thixotropy? Why is it important for adhesives?

Answer 318

What are the important parameters for successful bonding?

• Design of the joint
• Adhesive selection
• Surface preparation
• Substrate and conditions in service

Why is viscosity important?

• Dictates the application methods required for material use.
• High viscosity can be difficult to remove
• Low viscosity can flow to much and run off surfaces

Thixotropy: indication of a material’s decrease in viscosity over time while under stress.

Indicate an adhesives ability to fill gaps between substrates

Predict a product’s resistance to sagging vertical surfaces

Question 319

Why is lap shear strength important?

Why is peel strength important?

How are tensile properties are measured?

What is gel time?

Answer 319

Why is lap shear strength important?

• Gives a measure of ultimate load and a way of comparing adhesive strength
  
  • Cohesive failure: adhesive remains on both substrates, indicating a strong bond
  • Adhesive failure: adhesive remains on one substrate, indicating selection of the wrong adhesive for substrates

Why is peel strength important?

• Peel strength is a measure of a material’s ability to withstand vibration and stretching without deforming or breaking.
• Important indication of an adhesive’s toughnessand ability to produce joints that can withstand difficult service conditions

Tensile properties are measured by:

• Elongation: amount of stretch required to break a specimen
• Ultimate tensile strength

Gel time, work life and pot life are terms used interchangeably to indicate:

• The amount of time at room temperature from initial mixing until the mixture can no longer be stirred.
• Gel time can be increased or decreased by cooling or heating the resin or hardener

Question 322

What is AM?

Answer 322

What is AM?

• AM is the layer by layer deposition of material to make a part
• Additive manufacturing is a process where:
• Digital 3D design data is used to build up a component in layers by depositing material.
• 3D printing is increasingly used as a synonym for AM.
• However, AM is more accurate in that it describes a professional production technique which is clearly distinguishing from conventional methods of material removal.

Question 329

What are the drawbacks of AM?

Answer 329

What are the drawbacks of AM?

• Machine cost (barrier to entry, limited volume)
• Material cost
• Throughput
• Quality
• Process control
• Increased validation and demonstration, supported by standards for certification and process operation

Question 330

What are the different types of engineered ceramics?

What are their properties?

Answer 330

What are the different types of engineered ceramics?

• Oxides:
  
  • Aluminas
  • Quartz/silicates
  • Yttria
  • Zirconias
• Non oxides
  
  • Carbides
  • Nitrides

Material properties

• Harder and stiffer than steels
• More heat and corrosion resistant than metals or polymers
• Lower density than most metals and allows
• Raw materials are plentiful
• Display wide range of properties to facilitate use in different product areas

Question 333

What are the different applications for ceramics?

Answer 333

Applications of alumina:

• Beverage valves: hardness, rigidity, strength, corrosion resistant and inert
  
  • Improved lifetime
  • Improved portion control
  • Improved product quality
• Precision metering pumps: hard, rigid, strength, wear, corrosion resistant, biocompatible, inert
  
  • Accurate dosing and long life
  • Ceramic provides dimensional stability

Applications of zirconia

• Diesel engine injector link: hardness, strength, wear, corrosion resistant, thermal stability
  
  • Improved lifetime, reduced warranty claims, improved fuel economy

Applications of carbides

• Body armour: hardness, strength, weight
  
  • Lives saves, weight reduction, improved ballistic protection
• Satellite mirrors: rigidity, strength, weight, thermal conductivity and expansion
  
  • Strong, stiff and lightweight
  • Temperature capability, ultra-fine finish

Applications of nitrides

• Hybrid bearings: hardness, strength, wear, corrosion resistant, inert
  
  • Higher speeds and throughput
  • Improved runout and part accuracy
  • Cooler operation, less downtime