DFM Design Principles
- 3. Mechanical engineering designs generally include off-the-shelf components and fabricated parts. Knowing the strengths and limitations of the fabrication techniques makes for higher quality and more cost competitive designs.
- 4. 1. Simplicity 2. Standard Materials and Components 3. Standardized Design of the Product 4. Liberal Tolerances 5. Use Materials that are Easy to Process
- 5. 6. Teamwork with Manufacturing Personnel 7. Avoidance of Secondary Operations 8. Design to Expected Level of Production 9. Utilize Special Process Characteristics 10. Avoid Process Restrictiveness
- 6. Description: minimize the number of parts, intricate shapes, and manufacturing operations Motivation: generally provides reduced cost, improved reliability, easier servicing, and improved robustness Example: Braun Lift
- 8. Description: Use standard off-the-shelf parts and widely available materials Motivation: eases purchasing, simplifies inventory management, and avoids tooling investments Example: Screws
- 9. Description: For similar products, specify the same materials, parts, and subassemblies as much as possible. Motivation: provides economies of scale, simplifies operations, and simplifies inventory management Example: Braun Lift
- 10. Description: make tolerances as forgiving as possible Motivation: tight tolerances are expensive (in a non-linear fashion) (Fig in the next slide)
- 12. Description: take advantage of materials that have been developed for easy processibility Motivation: while material may cost more, it will often provide lower overall cost Example: “Free-Machining” Grades, Many polymer grades are tuned to a process
- 13. Description: collaborate with the people who will be producing your product (the earlier the better) Motivation: they provide a unique body of knowledge and useful insights Example:
- 14. Description: minimize the need for secondary operations Motivation: secondary operations (e.g. deburring, inspection, painting, and heat treating) can be as expensive as the primary manufacturing operation Example: Pre-painted steel, investment casting, MIM in firearms
- 15. Description: understand and take advantage of the special capabilities of various manufacturing processes Motivation: can often eliminate manufacturing operations and reduce the number of parts Example: injection molding snap fits and living hinges
- 16. Description: on part drawings, specify only the final characteristics needed; do not specify the process to be used Motivation: potential cost savings
- 17. Estimate the Manufacutring Costs Consider the Impact of DFM Decisions on Other Factors Recompute the Manufacturing Costs Reduce the Costs of Supporting Production Reduce the Costs of Assembly Reduce the Costs of Components Good enough ? N Y Acceptable Design Proposed Design
- 18. Estimate the manufacturing 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.
- 19. Finished GoodsManufacturing System Equipment Information Tooling WasteServicesSuppliesEnergy Raw Materials Labor Purchased Components
- 20. Sum of all the expenditures for the inputs of the system (i.e. purchased components, energy, raw materials, etc.) and for disposal of the wastes produced by the system
- 21. Manufacturing Cost OverheadAssemblyComponents Standard Custom Labor Equipment and Tooling Support Indirect Allocation Raw Material Processing Tooling
- 22. Component Costs (parts of the product) Parts purchased from supplier Custom parts made in the manufacturer’s own plant or by suppliers according to the manufacturer’s design specifications Assembly Costs (labor, equipment, & tooling) Overhead Costs (all other costs) Support Costs (material handling, quality assurance, purchasing, shipping, receiving, facilities, etc.) Indirect Allocations (not directly linked to a particular product but must be paid for to be in business)
- 23. Fixed Costs – incurred in a predetermined amount, regardless of number of units produced (i.e. setting up the factory work area or cost of an injection mold) Variable Costs – incurred in direct proportion to the number of units produced (i.e. cost of raw materials)
- 24. Understand the Process Constraints and Cost Drivers Redesign Components to Eliminate Processing Steps Choose the Appropriate Economic Scale for the Part Process Standardize Components and Processes Adhere to “Black Box” Component Procurement
- 25. Redesign costly parts with the same performance while avoiding high manufacturing costs. Work closely with design engineers—raise awareness of difficult operations and high costs.
- 26. Reduce the number of steps of the production process Will usually result in reduce costs Eliminate unnecessary steps. Use substitution steps, where applicable. Analysis Tool – Process Flow Chart and Value Stream Mapping
- 27. Economies of Scale – As production volume increases, manufacturing costs usually decrease. Fixed costs divided among more units. Variable costs are lower since the firm can use more efficient processes and equipment.
- 28. Black box—only give a description of what the component has to do, not how to achieve it Successful black box design requires clear definitions of the functions, interfaces, and interactions of each component.
- 29. Economies of Scale – The unit cost of a component decreases as the production volume increases. Standard Components—common to more than one product Analysis tools – group technology and mass customization