W6 Manufacturing Process Selection

Question 1

Design for Manufactrure DFM

Answer 1

Designing
products to facilitate their manufacture

Question 2

Design for assembly (DFA)

Answer 2

Designing
product to facilitate their assembly

Question 3

Process Selection Workflow

Answer 3

• Estimate production quantity
• Choose material type
• Identify technically capable processes
• Compare costs and capabiltiies
• Select the most economic process (loop back to point 2- consider alternative designs for components)
• Review the selected process against business requirements

Question 4

Process Selection drivers (at least 5)

Answer 4

• Product quantity
• Tooling costs
• Labour intensity and work patterns
• Maintenance
• Material costs and availability
• Component form and dimensions
• Surface finish needs
• Equipment costs
• Processing times
• Process supervision
• Energy consumption and other overhead costs
• Material to process compatibility
• Tolerance requirements
• Process waste

Question 5

PRIMAs (Process Informations Maps)

Answer 5

1. Obtain an estimate of the annual production quantity.
2. Choose a material type to satisfy the Product Design Specifications (PDS).
3. Refer to Figure 2.1 to select candidate PRIMAs.
4. Consider each PRIMA against requirements.
5. Compare process with alternatives.
6. Review process against business requirements.

Question 6

Classification of manufacturing processes

Answer 6

Based on mass change
* Subtractive- mass reduces in the process
* Transformative- mass remains the same during the process
* Additive- mass increases during the process

Question 7

Examples of Primary shaping Processes

Answer 7

Casting: Sand, Die and Investment Casting
Moulding: Injection moulding, blow moulding
Forming: Forging, presswork, rolling
Powder: Powder metal sintering
Special: Composite lay-up

Question 8

Examples of Secondary Processes

Answer 8

Bulk Heat Treatment: Hardening, tempering, annealing
Material Removal Processes: turning, drilling, milling, laser beam machining
Surface Treatment: Plating, painting, anodising, polishing

Question 9

Assembly/Test processes

Answer 9

Joining processes: Bolting, riveting, welding, brazing, soldering, adhesive, bonding
Assembly systems: Component feeding, orientation, robotics, placement, insertion
Test processes: Measurement, inspection and fucntional testing

Question 10

Over the wall design

Answer 10

*It is extremely uncommon, and a bad idea, for design to be separate from manufacturing
(this is sometimes called “over-the-wall design”)

Question 11

Concurrent Engineering

Answer 11

When the design engineers work with the manufacturing engineers, as well as with
other departments involved in the product, the activity is called concurrent engineering

Question 12

(Tranformative) Casting Processes

Answer 12

Sand casting, Shell moulding, Gravity die casting, Pressure die casting, Centrifugal casting, Investment casting, Ceramic mould casting, Plaster mould casting, Squeeze casting

Question 13

(Tranformative) Forming Processes

Answer 13

Forging, Rolling, Drawing, Cold forming, Cold heading, Swaging,
Superplastic forming, Sheet-metal shearing, Sheet-metal forming, Spinning, Metal injection moulding, Continuous extrusion

Question 14

Tranformative Plastic Processing

Answer 14

Injection moulding, [5.2] Reaction injection moulding, [5.3] Compression moulding, [5.4] Resin
transfer moulding, [5.5] Vacuum forming, [5.6] Blow moulding, [5.7] Rotational moulding, [5.10]
Continuous extrusion.

Question 15

Tranformative Surface processes

Answer 15

Thermal hardening and Shot peening

Question 16

Subtractive Manufacturing processes

Answer 16

[6] Machining, [7.1] Electrical discharge machining, [7.2] Electrochemical machining, [7.3] Electron
beam machining, [7.4] Laser beam machining, [7.5] Chemical machining, [7.6] Ultrasonic machining,
[7.7] Abrasive jet machining

Question 17

Additive manufacturing processes

Answer 17

Powder metallurgy, Contact moulding, Pultrusion, Stereolithography,
3D printing, Selective laser sintering, Laminated object manufacturing, Fused
filament fabrication, Carburising, Nitriding, Ion implantation, Anodising,
Chromating, Chemical Vapour Deposition, Physical Vapour Deposition, Electroless
Nickel, Electroplating, Hot dip coating, Thermal spraying, Welding, Brazing, Soldering, Thermoplastic welding, Adhesive bonding, Mechanical fastening techniques

Question 18

Motivation for Cost Considerations

Answer 18

• Allocate internal resources
• Establish the bid price of a product
• Verify quotations by suppliers
• Decide whether to buy or manufacture
• Evaluate product designs
• Examine viability of a product

Question 19

Direct Cost

Answer 19

Spent directly on making the
product, scales linearly with quantity produced. Includes
materials and labour.

Question 20

Indirect cost (Overheads)

Answer 20

All costs that cannot be directly attributed to a specific product
including:
* Manufacturing: Rent, heat, light, power, management staff, maintenance, depreciation,
cleaning, transport, safety, computer network, stores, production control, quality control,
production engineering etc.
* Business: Research, design, development, sales, marketing, finance, legal costs, directorate

Question 21

Time Categorisation of costs

Answer 21

Capital cost or fixed Cost: Cost of setting up the system (machines tools buildings equipment etc)
Yearly running Cost: Total expenses incurred in operating the manufacturing system during
a year – operators, materials, overheads, depreciation.

Question 22

Capital Costs

Answer 22

The fixed cost needed to commence operations:
* Facilities
* Equipment
* Permits and licenses
* Total fixed costs do not change
proportionally as volume of
activity changes.
* Per unit fixed costs change
inversely as activity changes.
(Eg: Land for a Wheat farm, A pub’s alcohol licensing costs)

Question 23

Running Costs

Answer 23

The amount spent repeatedly and regularly on enabling and
facilitating the operation:
* Labour
* Materials
* Overheads
* Total variable costs change
proportionately as volume of
activity changes.
* Per unit variable cost remain
constant as volume of activity
changes.
(Eg: Uranium pellets for a nuclear reactor, A pub’s alcohol licensing costs

Question 24

Cost Estimation approach: Bottom Up Activity Based Costing (ABC)

Answer 24

All activities are accounted for

Question 25

Cost Estimation approach: Bottom Up Volume Based Costing (VBC)

Answer 25

(traditional costing)
Somewhat simpler, activities are bundled

Question 26

Cost Estimation Approaches: Top down

Answer 26

• Statistical – past data & regression (will likely output a range)
• Parametric – mathematical model from product design
• Baseline – look at competitors

Question 27

Cost Estimation Challenges

Answer 27

Inexperienced analyst
Unreliable Data
Unrealistic assumptions
Historical cost databased not available
Data not normalised
Unreasonable program baselines
Overoptimism
New Processes
First time integration
Cutting edge technology
Obtaining data
Program instability
Complex technology
Diminishing industrial base
Unrealistic projected savings

Question 28

Depreciation

Answer 28

Depreciation can be defined as the capital cost divided by the number of years that the capital
purchase remains in use. (e.g. the price of CNC machine divided by the number of years it is usable).

Question 29

Bottom Up Approach

Answer 29

In bottom-up approaches, the cost of the product is viewed as an aggregate of the cost of the detailed
manufacturing processes

Question 30

Activity Based Costing (ABC)

Answer 30

Activity based costing (ABC): This bottom-up method for costing relies on assignment of
overheads based on all the activities that take place within the manufacturing system. The cost
of raw materials is added to that of machine setup, material handling, engineering design, quality
control and other activities. The cost of each activity, in turn, is calculated based on the given
figures for labour cost, equipment cost, depreciation, indirect labour, scrap rate, rework volume, etc.

Question 31

Volume Based Costing (VBC)

Answer 31

This bottom-up method is slightly simpler and the assignment of
the overheads to products is based solely on machining time or labour time. The equipment cost, indirect labour, scrap, rework and depreciation are added together in an aggregate
figure and then assigned to products based on the time it takes to manufacture a product

Question 32

Cost estimation (things that make it easy)

Answer 32

Detailed documentation available
Adequate cost reserve
Well defined
Risk analysis conducted
Stable program
Adequate budget
Historical data available
Well trained and experienced analysts