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TAM302 Engineering Design Principles

TAM302 Engineering Design Principles. Syllabus Topic: Design for Manufacture & Assemble (DFMA) Introduction. Course Instructor: Mike Philpott Director of Concurrent Design & Manufacture Lab Associate Professor of Mechanical Science & Engineering mphilpot@uiuc.edu. Mfg. Alternatives:

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TAM302 Engineering Design Principles

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  1. TAM302 Engineering Design Principles Syllabus Topic: Design for Manufacture & Assemble (DFMA) Introduction Course Instructor: Mike Philpott Director of Concurrent Design & Manufacture Lab Associate Professor of Mechanical Science & Engineering mphilpot@uiuc.edu

  2. Mfg. Alternatives: Investment/Cash Flow Decisions • Trade off: • Recurring Costs versus Non-Recurring Costs • Example: $60,000 tooling investment = $0.30 per part • $5 tooling investment = $95 per part Piece-part costs Tooling costs

  3. Mfg. Alternatives: Investment/Cash Flow Decisions Piece-part costs Tooling costs

  4. DFM: where M = Primary Mfg. Process Improve the design for manufacturability Select the Manufacturing Process Analyze Cost • Quote • Hist. data • Models • Software • Broad process knowledge • Comparative cost knowledge • Do's & Don'ts (Rules/checklist) • Cost-of-features knowledge

  5. Assembly typically occupies between 40% and 60% of the total production period. Design For Assembly (DFA) Select Assembly Method $ Analyze for Assembly Improve the design % • DFA principles • BDI handbook • Software (BDI, Sapphire, AEM) • Combine • Eliminate • Simplify • Manual • Robotic • Special purpose

  6. DFAExample

  7. Assembly Labor Hours per Car Japan 16 U.S. (Big 3) 25 Europe 36 Data Source: Detroit Free Press

  8. Savings resulting from the use of DFA techniques on Ford's TAURUS Carline have been estimated to be > $1 billion. DFA on Ford Taurus

  9.  Assembled blindfolded at DFA conf. in 1.5 mins.  Reduced number of parts by 80%  Reduced number of vendors by 65%  Eliminated special assembly tools  Estimated lifetime labor cost redn. of $1.1 million  Estimated savings from elimg. 1 screw $12,500 NCR 2760 Point-of-sale Terminal

  10. Assembly typically occupies between 40% and 60% of the total production period. Design For Assembly (DFA) Select Assembly Method $ Analyze for Assembly Improve the design % • DFA principles • BDI handbook • Software (BDI, Sapphire, AEM) • Combine • Eliminate • Simplify • Manual • Robotic • Special purpose

  11. B. 'Component' Design for Assembly The design of each component for ease of assembly to its neighbors. DFA Principles A. 'Product' Design for Assembly The design of the entire product with a view to overall ease of assembly.

  12. 1. Design for minimum number of parts Is there a way that reduces the number of required parts? Are all components essential or can their functions be achieved by modifying an existing component? Can components be combined into one and manufactured as an integral multifunctional component? A. 'Product' DFAPrinciple #1.

  13. Ex. Application of Principle #1. Old design= 8 parts New design= 3 parts

  14. Ex. Application of Principle #1. Old Design = 25 parts New Design = 2 parts

  15. 2. Minimize number of fasteners and their components Use snap fits where possible Use press fits where disassembly is not required Consider molded hinges, straps, or hook-unders  Rationalize fasteners - types, lengths etc.  Use one piece fasteners with lead in pilots  Design geometry for automatic alignment A. 'Product' DFA Principle #2.

  16. Ex. Applications of Principle #2. Hook-under design to minimize number of fasteners

  17. Use single-piece fasteners, with guide pilots Ex. Applications of Principle #2. or inserts

  18. Snap fits - can be designed for ease of assembly & disassembly Ex. Applications of Principle #2. Recess for release of snap

  19. Ex. Applications of Principle #2. Hinges, straps and/or snap fits: Living hinges & straps Snap fits

  20. Rocker-box example: Good ergonomics / style Ex. Applications of Principle #2.

  21. 3. Design the product for assembly from one direction  Where possible assemblies should be designed so that a base piece is established, and remaining parts assembled from one, ideally vertical (Z) direction.  It is difficult to feed components in from the side. A. 'Product' DFA Principle #3.

  22. 4. Avoid the need to turn the assembly over  If previously placed components have not been fastened, they may move out of position.  Datum and location points change, and complicate the assembly process, which leads to jamming and assembly failure. A. 'Product' DFA Principle #4.

  23. 5. Standardize on Components, Materials, and Fasteners Components can be difficult to differentiate, particularly small similar shaped ones.  It is relatively common for feeders to become jammed because wrong parts have been fed in by operators.  Considerable savings in storage, inventory, ordering etc. A. 'Product' DFA Principle #5.

  24. 6. Provide location surfaces that are closely related to datum surfaces  This ensures a known location tolerance for the automatic placing of components.  Care should be taken to avoid tolerance build-up. A. 'Product' DFA Principle #6.

  25. 7. Consider ease of disassembly for maintenance, service, repair, and recycling  Integral snap fits, press fits, and retaining clips (circlips) allow compact designs, but if care is not taken, result in impossible disassembly  Disassembly is frequently necessary due to incorrect assembly, the need to service/repair, and now the requirement to recycle A. 'Product' DFA Principle #7.

  26. 8. Adopt a modular design philosophy for the product group  Allows model variations to be accomplished at a sub-system level. Subassembly volumes increase, total parts decrease.  Modular sub-assemblies may be built and tested by specialist teams (higher quality). A. 'Product' DFA Principle #8.

  27. Modular Design Assembly time reduced from 540 hrs to 180 hrs Design time per crane = 350 man hrs - 18hrs Fabrication time = 1500 hrs to 550 hrs

  28. 9. Avoid the need for assembly adjustments  Eliminating adjustments will usually reduce assembly time considerably; and reduce service / maintenance  Equipment going out of adjustment is one of the biggest causes of customer dissatisfaction.  Spring loading can be used effectively to avoid assembly adjustment and to eliminate adjustment for wear. A. 'Product' DFA Principle #9.

  29. 10. Minimize assembly steps and extra operations  Each assembly step or operation must be resourced  Mistakes in assembly are one of the greatest cause of product malfunction and customer returns. The fewer the steps the fewer the opportunities for error.  Extra operations such as applying grease, sealants, turning part over etc. add to time and reduce assembly efficiency. A. 'Product' DFA Principle #10.

  30. Feeding the components: from a bin, bulk feeder (e.g. bowl feeder), or magazine, or continuous strips. Orienting the components: by human operator, by the feeder tracks, and by the robot / workhead. Positioning and Placing the components B. 'Component' Design for Assembly The design of each component for ease of assembly to its neighbors; i.e. the following tasks:

  31. 1. Components should be symmetrical or have exaggerated assymetry B. 'Component' DFA Principle #1 Symmetrical shapes have a predictable rest aspect  Non-symmetrical shapes have an unpredictable resting aspect  exaggerated assymetry and part falls on one of its flat faces 

  32. 2. Components should have the least number of important directions B. 'Component' DFA Principle #2 To reduce the chance of correct feeding and positioning: A is better than B A B is better than

  33. Where possible make chamfers and lead-in angles generous, and avoid sharp corners, to avoid jamming: B. 'Component' DFA Principle #3 3. Provide Lead-in or Chamfers

  34. 4. Components should be free from burrs and flash, and be smooth in surface finish. B. 'Component' DFA Principle #4 & #5 5. Design parts to prevent tangling: Often a small design change can eliminate the tendency of components to tangle. Close ends and keep material thickness greater than gaps and slots:

  35. Loosely tolerancing non-functional dimensions can cause problems if the feeding and orienting method is not considered - jamming may occur if components are at extremes of limit: B. 'Component' DFA Principle #4 & #5 6. Consider the dimensions important to feeding and orienting

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