Design for Manufacturing

1. Design for Manufacturing Teaching materials to accompany: Product Design and DevelopmentChapter 13 Karl T. Ulrich and Steven D. Eppinger5th Edition, Irwin McGraw-Hill, 2012.

2. Product Design and DevelopmentKarl T. Ulrich and Steven D. Eppinger5th edition, Irwin McGraw-Hill, 2012. Chapter Table of Contents: • Introduction • Development Processes and Organizations • Opportunity Identification • Product Planning • Identifying Customer Needs • Product Specifications • Concept Generation • Concept Selection • Concept Testing • Product Architecture • Industrial Design • Design for Environment • Design for Manufacturing • Prototyping • Robust Design • Patents and Intellectual Property • Product Development Economics • Managing Projects

3. Product Development Process Concept Development System-Level Design Detail Design Testing and Refinement Production Ramp-Up Planning How can we emphasize manufacturing issues throughout the development process?

4. Outline • DFX concept • DFM objectives • DFM method • Mfg. cost estimation • DFM impacts • DFM examples

5. Design for Manufacturing Example:GM 3.8-liter V6 Engine

6. Understanding Manufacturing Costs

7. Definition • Design for manufacturing (DFM) is a development practiceemphasizing manufacturing issues throughout the product development process. • Successful DFM results in lower production cost without sacrificing product quality.

8. Introduction • DFM is part of DFX • DFM often requires a cross-function team • DFM is performed through the development process

9. Major DFM objectives • Reduce component costs • Reduce assembly cost • Reduce production support costs

10. The DFM Process (5 steps) • Estimate the mfg. costs • Reduce the costs of components • Reduce the costs of assembly • Reduce the costs of supporting production • Consider the impact of DFM decisions on other factors.

11. Estimate mfg. costs • Cost categories • Component vs. assembly vs. overhead • Fixed vs. variable • Material vs. labor • Estimate costs for standard parts • Compare to similar part in use • Get a quote from vendors • Estimate costs of custom made parts • Consider material costs, labor costs, and tooling costs • Depend on the production volume as well • Estimate costs of assembly • Summing up all assembly operations (time by rate) • Estimate the overhead costs • A % of the cost drives

12. Reduce the costs of components • Identify process constraints and cost drivers • Redesign components to eliminate processing steps • Choose the appropriate economic scale for the part process • Standardize components and their processes • Adhere the black-box component

13. Reduce the costs of assembly • Integrate parts (using the Boothroyd method) • Maximize ease of assembly • Consider customer assembly (do-it-yourself) technology driven products

14. Reduce the costs of supporting production • Minimize systematic complexity (such as plastic injection modeling for one step of making a complex product) • Error proofing (anticipate possible failure modes in the production system and take appropriate corrective actions early in the development process)

15. Considering impacts • Development time • Development cost • Product quality • External factors such as • component reuse and • life cycle costs

16. Design for Manufacturing Example:1993 GM 3800cc V6 Engine Design

17. DFM example • Exhibit 13-15 on Page 274 • Unit cost saving of 45% • Mass saving of 66% (33 Kg.) • Simplified assembly and service procedures. • Improved emissions performance • Improved engine performance • Reduce shipping costs (due to lighter components) • Increased standardization across vehicle programs.

18. Cost Appendices • Materials costs • Exhibit 13-17 on page 279 • Component mfg. costs • Exhibits 13/18-21 on pages 280-283 • Assembly costs • Page 286 for common products • Page 287 for part handling and insertion times on Ex. 13-23 • Cost structures for firms on Ex 13-24.

24. Design for X – Design principles • Part shape strategies: • adhere to specific process design guidelines • if part symmetry is not possible, make parts very asymmetrical • design "paired" parts instead of right and left hand parts. • design parts with symmetry. • use chamfers and tapers to help parts engage. • provide registration and fixturing locations. • avoid overuse of tolerances.

25. Design for X – Design principles • Standardization strategy • use standard parts • standardize design features • minimize the number of part types • minimize number of total parts. • standardize on types and length of linear materials and code them. • consider pre-finished material (pre-painted, pre-plated, embossed, anodized). • combine parts and functions into a single part.

26. Design for X – Design principles • Assembly strategies 1 • design product so that the subsequent parts can be added to a foundation part. • design foundation part so that it has features that allow it to be quickly and accurately positioned. • Design product so parts are assembled from above or from the minimum number of directions. • provide unobstructed access for parts and tools • make parts independently replaceable. • order assembly so the most reliable goes in first; the most likely to fail last.

27. Design for X – Design principles • Assembly strategies 2 • make sure options can be added easily • ensure the product's life can be extended with future upgrades. • use sub-assemblies, especially if processes are different from the main assembly. • purchase sub-assemblies which are assembled and tested.

28. Design for X – Design principles • Fastening strategies 1 • use the minimum number of total fasteners • use fewer large fasteners rather than many small fasteners • use the minimum number of types of fasteners • make sure screws should have the correct geometry so that auto-feed screwdrivers can be used. • design screw assembly for downward motion • minimize use of separate nuts (use threaded holes). • consider captive fasteners when applicable (including captive nuts if threaded holes are not available).

29. Design for X – Design principles • Fastening strategies 2 • avoid separate washers and lockwashers (make it be captivated on the bolt or nut so it can still spin with respect to the fastener) • use self-tapping screws when applicable. • eliminate fasteners by combining parts. • minimize use of fasteners with snap-together features. • consider fasteners that push or snap on. • specify proper tolerances for press fits.

30. Design for X – Design principles • Assembly motion strategies • fastened parts are located before fastener is applied. • assembly motions are simple. • Assembly motions can be done with one hand or robot. • assembly motions should not require skill or judgment. • products should not need any mechanical or electrical adjustments unless required for customer use. • minimize electrical cables; plug electrical sub-assemblies directly together. • minimize the number of types of cable.

31. Design for X – Design principles • Automation handling strategies 1 • design and select parts that can be oriented by automation • design parts to easily maintain orientation • use parts that will not tangle when handled in bulk. • use parts what will not shingle when fed end to end (avoid disks). • use parts that not adhere to each other or the track. • specify tolerances tight enough for automatic handling. • avoid flexible parts which are hard for automation to handle.

32. Design for X – Design principles • Automation handling strategies 2 • make sure parts can be presented to automation. • make sure parts can be gripped by automation. • parts are within machine gripper span. • parts are within automation load capacity. • parting lines, spruces, gating or any flash do not interfere with gripping.

33. Design for X – Design principles • Quality and test strategies • product can be tested to ensure desired quality • sub-assemblies are structured to allow sub-assembly testing • testing can be performed by standard test instruments • test instruments have adequate access. • minimize the test effort spent on product testing consistent with quality goals. • tests should give adequate diagnostics to minimize repair time.

34. Design for X – Design principles • DF Maintenance strategies 1 • provide ability for tests to diagnose problems • make sure the most likely repair tasks are easy to perform. • ensure repair tasks use the fewest tools. • use quick disconnect features • ensure that failure or wear prone parts are easy to replace with disposable replacements • provide inexpensive spare parts in the product. • ensure availability of spare parts.

35. Design for X – Design principles • Maintenance strategies 2 • use modular design to allow replacement of modules. • ensure modules can be tested, diagnosed, and adjusted while in the product. • sensitive adjustment should be protested from accidental change. • the product should be protected from repair damage. • provide part removal aids for speed and damage prevention. • protect parts with fuses and overloads

36. Design for X – Design principles • Maintenance strategies 3 • protect parts with fuses and overloads • ensure any sub-assembly can be accessed through one door or panel. • access over which are not removable should be self-supporting in the open position. • connections to sub-assemblies should be accessible and easy to disconnect. • make sure repair, service or maintenance tasks pose no safety hazards. • make sure sub-assembly orientation is obvious or clearly marked.

37. Design for X – Design principles • Maintenance strategies 4 • make sure sub-assembly orientation is obvious or clearly marked. • provide means to locate sub-assembly before fastening. • design products for minimum maintenance. • design self-correction capabilities into products • design products with self-test capability. • design products with test ports • design in counters and timers to aid preventative maintenance. • specify key measurements for preventative maintenance programs • include warning devices to indicate failures.

38. Design for X – Design principles • Axomatic Design by Nam Suh • Axiom 1 • In good design, the independence of functional requirements is maintained. • Axiom 2 • Among the designs that satisfy axiom 1, the best design is the one that has the minimum information content.

39. Design for X – Design principles • Axiomatic design- corollaries • Decouple or separate parts of a solution if functional requirements are coupled or become coupled in the design of products and processes. • Integrate functional requirements into a single physical part or solution if they can be independently satisfied in the proposed solution. • Integrate functional requirements and constraints. • Use standardized or interchangeable parts whenever possible. • Make use of symmetry to reduce the information content. • Conserve materials and energy. • A part should be a continuum if energy conduction is important.

40. Design for X – Design principles • DFA Method: Boothroyd and Dewhurst • Apply a set of criteria to each part to determine whether, theoretically, it should be separated from all the other parts in the assembly. • Estimate the handling and assembly costs for each part using the appropriate assembly process - manual, robotic, or high-speed automatic.

41. Design for X – Design principles • Three criteria • Is there a need for relative motion? • Is there a need for different materials • Is there a need for maintenance?

42. Design for Assembly RulesExample set of DFA guidelines from a computer manufacturer. 1. Minimize parts count. 2. Encourage modular assembly. 3. Stack assemblies. 4. Eliminate adjustments. 5. Eliminate cables. 6. Use self-fastening parts. 7. Use self-locating parts. 8. Eliminate reorientation. 9. Facilitate parts handling. 10. Specify standard parts.

43. Design for Assembly • Key ideas of DFA: • Minimize parts count • Maximize the ease of handling parts • Maximize the ease of inserting parts • Benefits of DFA • Lower labor costs • Other indirect benefits • Popular software developed by Boothroyd and Dewhurst. • http://www.dfma.com

44. To Compute Assembly Time Handling Time + Insertion Time Assembly Time

45. Method for Part Integration • Ask of each part in a candidate design: 1. Does the part need to move relative to the rest of the device? 2. Does it need to be of a different material because of fundamental physical properties? 3. Does it need to be separated from the rest of the device to allow for assembly, access, or repair? • If not, combine the part with another part in the device.

46. Three Methods to Implement DFM 1. Organization: Cross-Functional Teams 2. Design Rules: Specialized by Firm 3. CAD Tools: Boothroyd-Dewhurst Software

47. DFM Strategy is Contingent Corporate Strategy Product Strategy Production Strategy DFM Strategy

48. Other Images