Design for Manufacture

Question 1

List three possible causes for manufacturing inconsistency in the diameter of a steel shaft.

Answer 1

Machine misalignments, tool wear, loose jig, material property variations, poorly controlled thermal environment.

Question 2

What does the variable z refer to in the context of quality control?

Answer 2

The number of standard deviations from the mean metric value that are acceptable for consumption.

Question 3

What values of z should be aimed for?

Answer 3

Between 4 and 7.5.

Question 4

Name a manufacturing philosophy spawned out of the desire to aspire to z=6.

Answer 4

Six sigma process capability.

Question 5

How can asymmetrically distributed part defects be avoided?

Answer 5

By regularly checking tool wear and machine settings.

Question 6

How is z defined?

Answer 6

z = t/sigma, where sigma is the standard deviation of the part metric and t is the (one-sided) tolerance magnitude.

Question 7

How is the process capability measure, Cp, defined?

Answer 7

Cp = t/3*sigma.

Question 8

For what value of Cp is a process ‘capable’?

Answer 8

1.33

Question 9

What is an unbiased estimator for the standard deviation of a sample?

Answer 9

sigma = sqrt(sum( (x - \bar{x})^2 )/ (N-1) )

Question 10

What is the purpose of the ‘House of Quality’ design method?

Answer 10

Converting customer requirements into engineering requirements.

Question 11

How would you produce a House of Quality design table?

Answer 11

List customer requirements to the left of the table. Weight them. List engineering requirements to the right of the table. Record weak, strong, and very strong relationships between these requirements and the customer’s desires using numbers. Compute scores for each engineering requirement by multiplying the customer requirement weights by their associated relationship scores. This results in a ranking of engineering requirements.

Question 12

What is a product’s ‘footprint’?

Answer 12

Essentially its brand.

Question 13

List five types of artefact order that a manufacturer might handle.

Answer 13

Engineer-to-Order: Designed and built to customer specifications.
Make-to-Order: Artefact is based on a standard design, but production is linked to the customer order and specifications.
Assemble-to-Order: Product is built to customer specification from a stock of existing components.
Make-to-Stock: Product is built against a sales forecast, then sold to customers from stock.
Ship-to-Stock: Similar to make-to-stock, but the stock is held by a retailer rather than the manufacturer.

Question 14

What is a module?

Answer 14

A module is a complete, integrated, product subassembly that can easily be inserted into a broader assembly.

Question 15

What are the advantages of modular units?

Answer 15

They are easy to maintain/replace, there is quality control over their assembly (making it easier to localize assembly faults), and they are sealed-for-life.

Question 16

What are the disadvantages of modular units?

Answer 16

Small defects in modules cannot repaired (replacing them may also be expensive), and often they must be high-volume in order to offset associated design and manufacturing costs.

Question 17

What is platform design?

Answer 17

When the members of a product family use a common set of modules or components that are designed in-house.

Question 18

What are the advantages of platform design?

Answer 18

It is easier to manage inventory (since there are fewer parts), developments costs are reduced (since design work is not repeated), quality is increased (since design work can be focused on fewer components), greater product variety can be achieved (since components can be mixed and matched), and there is global standardization (which is convenient and reduces expense).

Question 19

How can product mass and volume be minimized?

Answer 19

By designing integrated products with as few interfaces as possible.

Question 20

How can assembly complexity be minimized?

Answer 20

By producing a modular design that has standardized part interfaces.

Question 21

List the advantages of modular design.

Answer 21

• Ease of maintenance
• Dividing labour is easier
• Makes it easier to test a design
• Allows technologies to be easily integrated
• Enables platform design

Question 22

How might the recyclability of a product be affected by modularity?

Answer 22

High-level disassembly is easier, but low-level disassembly is harder. Remanufacturing becomes possible with modules (i.e. re-using the entire module).

Question 23

List six quality-management tools.

Answer 23

BS 7000 Design Management Systems
ISO 9000 Quality Assurance
Total Quality Management
Six-sigma
Lean manufacturing
Poka-yoke

Question 24

What six areas does the BS 7000 provide advice on?

Answer 24

Managing innovation, managing the design of manufactured products, managing service design, managing design in construction, managing inclusive design.

Question 25

What four standards are contained within the ISO 9000 series?

Answer 25

ISO 9001:2015: Quality management systems - requirements
ISO 9000:015: Quality management systems - fundamentals and vocabularly
ISO 9004:2009: Quality management systems - managing for the sustained success of an organization
ISO 19011:2011: Guidelines for auditing management systems

Question 26

What three ideas underpin Total Quality Management?

Answer 26

1. Prevention rather than inspection.
2. Right first time.
3. Continuous quality improvement.

Question 27

What is Six Sigma?

Answer 27

Six Sigma is a quality management technique by which statistical tools are used to improve manufacturing quality by elimination of defects.

Question 28

How many parts per billion does a six-sigma quality assurance correspond to (assuming the magnitude of defect is a normally distributed r.v.)?

Answer 28

2 parts per billion.

Question 29

What is ‘Lean Manufacturing’?

Answer 29

A production philosophy that aims to reduce waste without sacrificing productivity.

Question 30

What is ‘waste’ in Japanese?

Answer 30

Muda

Question 31

What is ‘waste associated with uneven workloads’ in Japanese?

Answer 31

Mura (‘village’)

Question 32

What is a poka-yoke mechanism?

Answer 32

Any mechanism in a lean manufacturing process that helps an equipment operator avoid (yokeru) mistakes (poka).

Question 33

Who developed poka-yoke?

Answer 33

Shigeo Shingo of Toyota, Japan.