DESIGN FOR MANUFACTURING AND ASSEMBLY.A really good insight of DFA and DFM. Also includes a very precise and appealing caste study on aimplemention of DFMA on a motor drive assembly.

1. DESIGN FOR
MANUFACTURING
AND ASSEMBLY
PREPARED BY-
PRASHANT TRIPATHI

2. Index
 What is DFMA?
 Methodology
 Principles of DFMA
 Introduction to assembly
 Design for assembly
 Which parts are essential?
 DFA Index
 Throwback
 Introduction to DFM
 Major DFM objectives
 Estimating Manufacturing Costs
 Whys use DFMA?
 Reasons for not implementing DFMA
 Case study
 Other example-Reticle assembly for a thermal gunsight
 DFMA Software
 Bibliography

3. What is DFMA?
 A set of guidelines developed to ensure that a product is designed so that it can
be easily and efficiently manufactured and assembled with a minimum of effort,
time, and cost.
 Products designed using DFMA principles should have higher quality and
reliability than others.
 DFMA also ensures that the transition from the design phase to the production
phase is as smooth and rapid as possible.

4. Optimal Thinking is the core of all activities.
What is DFMA? (contd)
 It is a concurrent engineering team approach.
 The best results occur when DFMA is used in the product conceptual stage.
 The cross-functional team work towards minimizing the number of components,
manufacturing steps and operations while designing to proven manufacturing
capabilities.

5. Methodology

6. Principles of DFMA
1. Minimize part count
2. Make Parts Multi-Functional
3. Design parts to be self-aligning and self-locating.
4. Use stack assemblies.
5. Ensure the ease of handling of parts from bulk.
6. Eliminate Interfaces.
7. Design parts that cannot be installed incorrectly.
8. Maximize part symmetry if possible or make parts obviously asymmetrical.
9. Use Standard Parts and Hardware
10. Simplify and Optimize the Manufacturing Process
11. Encourage modular assembly

7. 1. Minimize part count
 The final cost of a product is directly proportional to the number of parts. As the
number of parts is reduced, product quality and reliability typically increase
 A Simple Test to Determine if a Part Can Be
Eliminated
• Must the part move relative to other parts in
performing its function?
• Must the part be made of different material?
• Must the part be a separate component?
 If the answer to these three questions is "NO", then the possibility of combining the
part with other parts should be considered.

8. 2. Make Parts Multi-Functional
 Multi-functional parts combine several functions into one part and reduce
complexity.

9. 3. Design parts to be self-aligning
and self-locating.
• Self aligning parts can be placed into an exact location
with no adjustment required.
• This makes assembly easier and faster for the
assembly workers.
• Examples of self-locating features include projections,
indentations, chamfers, molded keyways, etc.

10. 4. Use stack assemblies
• Assembly operations should use, not fight, gravity.
• One way to do this is to design parts for stack assembly
(i.e., assembly components from the bottom up).
• Requires less reorientation of the components which
speeds the assembly process.
• Not using gravity generally requires the use of additional
tooling and fixturing.

11. 5. Ensure the ease of handling of parts from bulk
 Parts should be designed with
handling in mind.
 Components should not get
tangled/nested together when
mixed together in a box or a bin.
 Minimize the potential for
becoming tangled or stuck
together.

12. Handling difficulty
size slipperiness
flexibililtysharpness

13. 6. Eliminate interfaces
 Interfaces increase the cost of an assembly.
 Each interface doubles the amount of information
required and increases overall assembly time.
 Eg : 2 sets of dimensions, 2 sets of tolerances, 2
sets of interface features, assembly labour,
assembly materials, etc.

14. 7. Design parts that cannot be installed incorrectly.
• Use physical obstructions to stop components
being fitted in the wrong place, or the wrong
way round.
• The name for this is “Poka-yoke”.
• Mistake-proofing

15. 8. Maximize part symmetry if possible or make parts
obviously asymmetrical.
• These irregularly-sized and spaced holes force the
worker to figure out which way it fits
• The addition of a flat side or similar feature helps to
achieve correct orientation during manual assembly
(but symmetry would probably be better)
• Make components fit either way round
whenever you can.
• Ideally, parts will have rotational and end-to-end
symmetry.

16. 9. Use Standard Parts and Hardware
 Standardization requires increased communication between the design teams.
 Reduces the number of tools required for assembly and lowers assembly cost.
 In order to facilitate the use of standard parts, the design team should utilize
various resources such as the preferred parts lists, standard parts manuals, vendor
catalogs, trade magazines, etc.

17. 10. Simplify and Optimize the Manufacturing Process
 Simplification and optimization of the manufacturing process reduces recurring
direct and overhead costs.
 Using processes that are easily controllable.
 Avoiding, where possible, processes that are difficult to control (i.e., welding,
brazing, etc.).
 Performing like operations simultaneously.

18. 11. Encourage modular assembly
 Modularize multiple parts into single sub-assemblies
 Simplifies assembly operations and make problem
identification easier by reducing the number of parts.
 Modular assembly also simplifies inventory and
improves maintenance and serviceability.
 By designing parts as separate, self-contained modules,
disassembly time is reduced, fewer tools are required,
and overall repair time is reduced.

19. Introduction to assembly
 Product of a complex design process.
 Designers can have a major influence on the cost and quality of an assembly.
 The assembly task also involves…
 Storing
 Handling
 Positioning
 Joining
 Adjusting
 Securing
 Inspection

20. Design for Assembly (DFA)
This forms a significant part of Design for Manufacture (DFM) – sometimes
considered together as DFMA.
Simplifies the product structure since the total number of parts in a product is a key
indicator of design quality.
Optimizes manual as well as automated assemblies.

21. Which Parts are Essential?
Both the Boothroyd & Dewhurst, and Lucas methodologies use the idea of
fundamental or essential parts.
All non-essential parts should be evaluated in case they can be designed out.
The Lucas methodology labels parts as ‘A’ (essential) and ‘B’ (target for
designing out).
Boothroyd & Dewhurst use ‘1’ and ‘0’, but the result is similar.

23. DFA Index
 An essential ingredient of the DFA method.
 DFA index is the assembly time for an "ideal" design divided by the total
assembly time and expressed as a percentage.
 The DFA index is a figure obtained by dividing the theoretical minimum
assembly time by the total assembly time.
The equation for calculating the DFA index Ema is,
Ema = Nmin .ta
tma
Where,
Nmin : minimum item count
ta : theo. minimum assembly time
tma : total assembly time

24. #Throwback…
 The first success resulting from the application of DFA in industry were reported in an article in
Assembly Engineering.(late 1970’s)
 In the article, Sidney Liebson , corporate director of manufacturing for Xerox suggested that
‘’DFA would save his company hundreds of millions of dollars over the next ten years.’’
 U.S. designers preferred to use the new computers rather than perform hand calculations to
analyze their designs for ease of assembly. As a result, engineers at IBM and Digital funded the
development of versions of the DFA software to run on their own company products.
 A major breakthrough in DFA implementation was made in 1988 when Ford Motor Company
reported that DFA software had helped them save billions of dollars on their Taurus line of
automobiles.

25. Introduction to DFM
 DFM is the method of design for ease of manufacturing of the collection of parts.
 Minimizes complexity of manufacturing operations.
 Like DFA ,DFM also shortens the product development cycle time.
 It is concerned with reducing overall part production cost.
 It seeks to utilize standards to reduce the costs.

26. Major DFM objectives
1) Estimate the mfg. costs
2) Reduce the costs of components
3) Reduce the costs of assembly
4) Reduce the costs of supporting production
5) Consider the impact of DFM decisions on other factors.

27. Estimating manufacturing costs.

28. Why use DFMA?
 Encourages dialogue between designers and the manufacturing engineers. This means that
teamwork is encouraged and the benefits of simultaneous or concurrent engineering can be
achieved.
 Lower Assembly Cost and Time
 Increased Reliability
 Shorter Total Time-To-Market
Since products developed using DFMA make the quickest and smoothest transition into the production phase,
the time for a product to go from conception to the consumer (total time-to market) is reduced.
Another reason why careful consideration of manufacture and assembly should be considered early in the
design cycle is because it is now widely accepted that over 70% of final product costs are determined during
design.

29. Reasons for not implementing DFMA
 No Time
 Not Invented Here
 The Ugly Baby Syndrome
 Low Volume
 DFMA Leads to Products That Are More Difficult to Service
 I Refuse to Use DFMA

30. Fig :Configuration of required motor drive assembly

31. Fig : Proposed design of motor drive assembly (dimensions in inches).

32. Results of Design for Assembly (DFA) Analysis for the Motor Drive Assembly Proposed Design

33. Results of Design for Assembly (DFA) Analysis for the Motor Drive Assembly Redesign

34. Fig : Redesign of motor drive assembly following design for assembly (DFA) analysis.

35.  The second step in an analysis is Design for Manufacture (DFM).
 By using DFM, early cost estimates for the parts are obtained for both the
original design and the new design in order to make trade-off decisions.
 During this process the best materials and processes to be used for the various
parts are considered.

36. Comparison of Parts Cost for the Motor Drive Assembly Proposed Design and Redesign
(purchased motor and sensor subassemblies not included)

37.  This is an indication that it is important not only to know the total estimated
manufacturing cost of an item but, more importantly, to know the cost of
providing the various features.
 This case study is typical in the sense that although DFA means design for
assembly, the results of improving assemblability usually manifest themselves
in significant reductions in part manufacturing costs.

39. Other example
• Original design of a reticle assembly for a
thermal gunsight in a US tank, made by
Texas Instruments, Inc.
• There are a large number of fasteners.
• Redesigned thermal gunsight
reticle: simpler to assemble, and
less to go wrong!
24 parts Only 8 parts

40. Measuring Improvement
Original Redesign Improvement
Assembly time (h) 2.15 0.33 84.7%
Number of different parts 24 8 66.7%
Total number of parts 47 12 74.5%
Total number of operations 58 13 77.6%
Metal fabrication time (h) 12.63 3.65 71.1%
Weight (lb) 0.48 0.26 45.8%

41. DFMA Software
 Boothroyd Dewhurst, Inc. has developed a software package to implement DFMA
techniques.
 Calculates the costs involved for different materials and manufacturing processes as well
as identify areas where the number of parts can be reduced.
 Easily considers the impact of using alternative materials and manufacturing processes.
 Documented significant reductions-
parts count and cost (51% and 37%)
time to market (50% faster)
assembly time (62%)
manufacturing cycle time (57%)
improved quality and reliability (68%) by system users.

42. Bibliography
 capacify.wordpress.com
 www.slideshare.net
 Product Design for Manufacture and Assembly: Second Edition, Revised and
Expanded, Geoffrey Boothroyd, Peter Dewhurst, and Winston Knight
 scholar.google.co.in
 www.dfma.com

43. “The best design is the simplest one that works”
- Albert Einstein

44. THANK YOU!!