Design for manufacturing and assembly
From DDL Wiki
Design for manufacturing and assembly (also called DFM, DFA, or together DFMA) refers to the set of tools, methods and processes for analyzing the manufacturing consequences of design decisions and improving a design in order to reduce manufacturing cost and complexity.
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DFMA Guidelines
DFMA guidelines and checklists provide heuristics that, when followed, tend to reduce complexity and cost of production. The general idea is that if the designer has these heuristics in mind during conceptual design and detailed design, she can make better decisions from a manufacturing perspective. Guidelines and checklists are only rules-of-thumb, and in some cases rules may contradict one another. Using checklists is generally helpful but is not a substitute for involving a manufacturing engineer in the design process.
Fabrication
Some typical guidelines used to generally improve manufacturing include:
- Simplify the design, reduce the number of parts
- For higher volume parts, consider castings or stampings to reduce machining
- Use near net shapes for molded and forged parts to minimize machining and processing effort.
- Design for ease of fixturing by providing large solid mounting surfaces & parallel clamping surfaces
- Avoid designs requiring sharp corners or points in cutting tools - they break easier
- Avoid thin walls, thin webs, deep pockets or deep holes to withstand clamping & machining without distortion
- Avoid tapers & contours as much as possible in favor of rectangular shapes
- Avoid undercuts that require special operations & tools
- Avoid hardened or difficult machined materials unless essential to requirements
- Put machined surfaces on same plane or with same diameter to minimize number of operations
- Design workpieces to use standard cutters, drill bit sizes or other tools
- Avoid small holes (drill bit breakage greater) & length to diameter ratio > 3 (chip clearance & straightness deviation)
- Design within process capabilities
Assembly
Some typical guidelines used to generally improve assembly include:
- Reduce the parts count
- Standardize and use common parts and materials
- Use modular design
- Don’t fight gravity
- Reduce processing surfaces
- Process in the open
- Eliminate fasteners - efficient fastening
- Design for part identity
- Optimize part handling
- Provide nesting features
- Optimize manufacturing process sequence
- Minimize flexible parts and interconnections
References
- Boothroyd, Dewhurst and Knight "Product Design for Manufacture & Assembly" CRC
Links
- DRM Associates has a nice page on DFMA here: http://www.npd-solutions.com/dfmguidelines.html
- Boothroyd and Dewhurst (who have written a number of books on DFMA) also sell software to support it: http://www.dfma.com/
