EML 4550: Engineering Design Methods

1. EML 4550: Engineering Design Methods Design for Manufacturing (Brief Introduction) Ulrich and Eppinger: Chapter 9

2. Definitions • “Design for…”: reliability, availability, serviceability, environment, cost…. “DFX” • Design for Manufacturing (DFM) • Very important aspect of the design/development cycle • Integrated throughout design process • Interdisciplinary and Multi-departmental (design, manufacturing, and production engineers, materials selection, accounting, purchasing, etc.) • Ensure that the product being designed can be manufactured at minimum cost while maintaining repeatability and quality

3. DFM Overview • Estimate the manufacturing costs • Reduce the cost of components (DFM) • Reduce the cost of assembly (DFA) • Reduce the cost of supporting production • Consider the impact of DFM on other aspects of the product DFMA

4. Good Enough? DFM Flowchart Proposed Design Estimate the Manufacturing Cost Reduce the Cost of Components Reduce the Cost of Assembly Reduce the Cost of Production Support Consider the Impact Of DFM on other Factors Recalculate the Manufacturing Cost N Y Acceptable Design

5. Estimating Manufacturing Costs Raw Materials Software demo from BDI Purchased Parts Labor Equipment Manufacturing System Finished Product Tooling Information Energy Waste Supplies Services

6. Elements of the Manufacturing Cost Components Overhead Assembly Standard Support Labor Indirect Allocation Custom Equipment And Tooling Raw Material Processing Tooling

7. Elements of the Manufacturing Cost • Components • Standard or custom parts; raw materials, processing, or tooling; purchased or in-house • Assembly • Equipment and tooling plus labor needed to manufacture product • Overhead • Support • Purchasing, QA, shipping & receiving, maintenance, etc. • Indirect • Administration, security, legal, etc.

8. Elements of the Manufacturing Cost • Fixed (independent of the number of units produced) • Special tooling • Tool set-up • Variable (proportional to the number of units produced) • Raw materials • Purchased parts • Assembly labor

9. The Bill of Materials

10. Reducing Component Cost • Understand Process Constraints and Cost Drivers • Take into account production cost early in the design phase • Do not specify tight tolerances if not needed • Do not ‘over-specify’ part qualities (surface finish, etc.) • Focus on the part functionality and design accordingly • Bear in mind limitations of production equipment (in terms of limits, rates, and complexity) • Sometimes the manufacturing limitations can easily be quantified and are repeatable, but oftentimes the ‘experience’ of the those involved need to be invoked. Work closely with Production.

11. Reducing Component Cost • Redesign Components to Eliminate Processing Steps • Consider eliminating steps that may not contribute to part functionality (paint, surface finish, etc.) • Try to design parts that can be manufactured in ‘one-step’ (molding, casting, extrusion, etc.) • If more steps are needed try to use ‘standard’ procedures (cutting to length, drilling hole, simple machining, etc.)

12. Reducing Component Cost • Choose the Appropriate Economic Scale for the Part Process • Use ‘economies of scale’. Part cost decreases as production volume increases • Determine ‘breakeven’ production volumes to decide among different processes (fixed vs. variable costs) Process A Process B $/unit Breakeven Point Number of parts manufactured

13. Reducing Component Cost • Standardize Component and Processes • Economies of scale applied at the component level • Better quality at lower cost if part is purchased from a major supplier (that has already specialized in the production of that component) • Increase supplier platform (availability and price) • Standardize across product platforms (same part for more than one product)

14. Reducing Component Cost • Adhere to “Black Box” Component Procurement • Japanese technique to specify only the functionality of the part but not the part • Leave supplier with freedom to produce best “black box” • In essence ‘subcontracting’ and avoiding a large portion of the design effort

15. Reducing Assembly Cost • Keeping Score • Maintain an ongoing estimate of assembly cost and be mindful of ‘assembly efficiency’ • Manufacturing Efficiency Index = 3 seconds x (minimum # of parts)/(estimated assembly time) • ‘3 seconds’ is the minimum required to handle and position a part • Minimum number of parts: • Does the part move relative to the rest of the assembly? • Does the part need to be made of different material than the rest of the assembly? • Does the part need to be removed for service or replacement?

16. Reducing Assembly Cost • Integrate Parts • If a part does not qualify as such according to the criteria given above, then it is a candidate to be integrated to another part • Eliminate assembly • Less expensive to fabricate • Clear definition of function • In some instances it is best to dis-integrate parts to reduce manufacturing costs (e.g., shape considerations to utilize different manufacturing methods)

17. Reducing Assembly Cost • Maximize ease of assembly • Insert part from top of assembly • Self-aligning parts • Part is indifferent to orientation • Assembly is possible with one hand • No tools required • Assembly requires a single linear motion • Part is secured upon insertion • Consider Customer Assembly

18. Reducing Support Cost • Minimize Systemic Complexity • Create quantifiable way to keep track of ‘complexity’ and strive to reduce it • Error Proofing • Anticipate error modes or possible failures to be encountered during manufacturing (equivalent to FMECA in Design for Reliability)

19. Consider Impact of DFM • Impact on Development Time • Economic model to ensure that by saving $ on manufacturing cost we do not increase development time • Impact on Development Cost • Same as above but for development cost • Impact on Product Quality • Reduce manufacturing cost but not at expense of quality • Impact on External Factors • Possible ramifications to other projects within the company: component reuse, • Possible ramifications to customers and society: life-cycle cost (save on manufacturing and ‘transfer’ cost to consumer), environmental issues (toxics, disposal, etc.)