Dfa for industry

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DFA
• Goals of this class:
– – – – Place DFA in context Learn basic principles of Design for Assembly Understand background and history Understand its strong and weak points

© Daniel E Whitney

“The Multiplier” According to Ford and GM or: Why Is DFM/DFA Important?
• For every product part, there are about 1000 manufacturing equipment parts* • Or, for every toleranced dimension orfeature on a product part, there are about 1000 toleranced dimensions or features on manufacturing equipment • Such “equipment” includes fixtures, transporters, dies, clamps, robots, machine tool elements, etc
*Note: Ford’s estimate is 1000, GM’s is 1800. Both are informal estimates.
© Daniel E Whitney

A Few Quotes
• Just because you can make something doesn’t mean you can manufacture it. • It’svery hard to make cheap [low cost] stuff - you get buried by your mistakes. • I don’t understand why it won’t assemble. It passed inspection. • Word came down that we couldn’t use screws. So we used snap fits. Then word came down that it had to pass a drop test. So we dropped it and it fell apart...
© Daniel E Whitney

Goals of DFM/DFA
• Historically, conventionally
– reduce costs, simplifyprocesses – improve awareness of manufacturing issues during design

• More broadly (a goal of this course)
– align fabrication and assembly methods to larger goals
• ability to automate, systematize, raise quality, be flexible • access to assembly-driven business methods like delayed commitment • innovative designs, outsourcing (Siemens intake manifold)

• Inevitably pushes DFM/DFA earlierinto the product development process where it blends with architecture
(see AITL Basic Issues and Product Architecture classes)
© Daniel E Whitney

Complete Outsourced Subassembly
AIR CLEANER

FUEL

INJECTORS

FUEL PRESSURE REGULAT OR

INTAKE AIR T EMPERAT URE SENSOR INT EGRAT ED FUEL RAIL

INTAKE

MANIFOLD

AIR FLOW SENSOR

THROTTLE

BODY

IDLE SPEED CONTROL

CourtesySiemens VDOAutomotive.

Used with permission.

© Daniel E Whitney

The Assembly from Heaven*
• Can be assembled one-handed by a blind person wearing a boxing glove • Is stable and self-aligning • Tolerances are loose and forgiving • Few fasteners • Few tools and fixtures • Parts presented in the right orientation • Parts asymmetric for easy feeding • Parts easy to grasp and insert
*DrPeter Will, ISI © Daniel E Whitney

The Assembly from Hell
• The opposite in each case from the previous slide

© Daniel E Whitney

History of DFA
• Deep background in Group Technology
– classification schemes

• European design tradition • Value Engineering
– each part must be justified

• Boothroyd
– – – – – part feeding physics - 1960s part handling and insertion experiments-1970’s assertion that assembly cost = 30 - 50% of manufacturing cost DFA methodology and software - 1970’s-80’s switch to assertion that parts are the main cost and fewer parts = less cost, even if those parts are more complex
© Daniel E Whitney

Sample Cost Breakdowns
• VCRs: 90% parts, 5% labor • Car engines: 75% parts, 7% labor, 7% capital, 7% consumables* • Mini computers: 65% parts, 25% labor• Fighter planes: 50% parts and tooling, 40% labor • Most of the above are pretty crude estimates because, for the most part, companies do not really know their costs
*Data from 27 engine lines, International Motor Vehicle Program

© Daniel E Whitney

Characteristics of Traditional DFA
• Uses an easy to understand metrics-driven approach (metrics
story about demurrage)

• Uses a relativecost and time metric • DFA in the small simplifies each assembly step
– – – – single parts manual assembly small parts uses many context-free metrics to assess difficulty levels of feeding and handling

• DFA in the large emphasizes part count reduction
– It is essentially another force in product architecture – Advanced plastics make part count reduction more attractive

© Daniel E...
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