DFM & DFA

Question 1

What are the potential benefits of DFM / DFA ? (6)

Answer 1

1) Reduce part count - less stock + better reliability
2) Systematic component costing
3) Lower component and assembly costs
4) Standardised components, assembly sequence across product family
5) Faster product development and reduced time to market
6) Lower level of engineering changes and modifications

Question 2

What are the issues with DFM/DFA in its application (5)

Answer 2

1) Needs to management led
2) Training needed
3) Additional resource needed
4) Many subjective aspects
5) Manufacturing and technical feasibility of new designs need to be tested

Question 3

What are the four stages of DFMA (CSC)

Answer 3

Phase 1 - Functional analysis - RIGHT PARTS?
a - classify parts as essential ‘a’ and non essential ‘b’
b - redesign around essential parts - reduce part count

Phase 2 - Manufacturing analysis HOW EASY TO MAKE THEM?
a - cost calculated on materials + manufacturing processes
b - ideas for part count reduction tested

Phase 3 - Handling analysis CAN WE HANDLE THEM?
a- correct orientation before assembly - modify if needed
b - Poka-Yoka devices to help ensure zero defects

Phase 4 - Fitting analysis CAN WE PUT THEM TOGETHER?
a - assembly sequence plan + assess difficulty
b - use DFA

Question 4

What are some of the DFM guidelines? (10)

Answer 4

1) Identify critical characteristics (tolerances + finishes)
2) Identify factors that influence their manufacture
3) Establish max tolerances
4) Avoid tight tolerances
5) Determine process capability to meet tolerance early
6) Design to be easily inspectable
7) use standard manufacturing processes
8) minimise number of re-orientation
9) generous radii/fillets on casts and moulds
10) design for ease of tooling and jigging

Question 5

What is design for assembly? Give some examples (8)

Answer 5

DFA covers techniques that assist in evaluating the assemblability of a design and provides guidelines on how to minimise assembly costs.

1) reduce part count
2) reduce the number of fasteners
3) modularise the design - multi use
4) design for optimise assembly - use gravity
5) minimise handling + re-orientation
6) Design parts which can’t be orientated incorrectly
7) Self aligning and self location
8) Eliminate adjustments

Question 6

What are the 3 key questions to consider on the DFMA questions?

Answer 6

1) what efficiency has the part count reduction achieved?
2) how have the manufacturing processes you need changed?
3) will it be difficult to maintain the key characteristics or tolerances?