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Design for Manufacturing and Assembly I General Principles Manufacturing and Product Design San Jos State University Design for Manufacturing and Assembly Terminology Design for DFx Design for Manufacturing DFM refers to design activity that is based on minimizing the cost of production and or time to market for a product while maintaining an appropriate level of quality A primary strategy in DFM involves minimizing the number of parts in a product Design for Assembly DFA involves making directions and methods for attaching and joining the parts of a product simpler DFMA refers to working both of these concepts together Tech14x Dr Seth Bates 2 Benefits of DFM and DFA Reduces part count thereby reducing cost If a design is easier to produce and assemble it can be done in less time so it will be less expensive Design for manufacturing and assembly should be used for that reason if no other Increases reliability If the production process is simplified there is less opportunity for errors Generally increases the quality of the product for the same reason that it increases the reliability Tech14x Dr Seth Bates 3 DFM and DFA DFM and DFA start with the formation of a design team which must be multi disciplinary including engineers manufacturing managers cost accountants and marketing and sales professionals The most basic simplest approach to Design for Manufacturing and Assembly is to apply a set of design guidelines You should use design guidelines with an understanding of explicit design goals Make sure that the application of each guideline improves the design concept with respect to those goals Tech14x Dr Seth Bates 4 DFM and DFA Design Guidelines Minimize part count by incorporating multiple functions into single parts Several parts could be fabricated by using different manufacturing processes sheet metal forming injection molding Ask yourself if a part function can be performed by a neighboring part Tech14x Dr Seth Bates 5 DFM and DFA Design Guidelines Modularize multiple parts into single sub assemblies Tech14x Dr Seth Bates 6 DFM and DFA Design Guidelines Design to allow assembly in open spaces not confined spaces Do not bury important components Tech14x Dr Seth Bates 7 DFM and DFA Design Guidelines Parts should easily indicate orientation for insertion Parts should have self locking features so that the precise alignment during assembly is not required Or Provide marks indentation to make orientation easier Tech14x Dr Seth Bates 8 DFM and DFA Design Guidelines Use standardized products and Standardize parts to reduce variety of operations choices and inventory burden Tech14x Dr Seth Bates 9 DFM and DFA Design Guidelines Design parts so they do not tangle or stick to each other Do Don t Tech14x Dr Seth Bates DO 10 DFM and DFA Design Guidelines Distinguish apparently similar parts Distinguish different parts that are shaped similarly or hard to distinguish by non geometric means such as color coding Tech14x Dr Seth Bates 11 DFM and DFA Design Guidelines Design parts to prevent nesting Nesting is when parts that are stacked on top of one another clamp or stick to one another for example cups and coffee lids Tech14x Dr Seth Bates 12 DFM and DFA Design Guidelines Design parts with orienting features to make alignment easier Tech14x Dr Seth Bates 13 DFM and DFA Design Guidelines Provide alignment features on the assembly so parts are easily oriented Do Tech14x Dr Seth Bates 14 DFM and DFA Design Guidelines Design the mating parts for easy insertion or attachment Provide allowance tolerance on each part to compensate for variation in part dimensions Case I Case II Tech14x Dr Seth Bates 15 DFM and DFA Design Guidelines Design the first part large and wide for stability then assemble smaller parts on top of it sequentially Case I Case II Tech14x Dr Seth Bates 16 DFM and DFA Design Guidelines If you cannot assemble parts from the top down exclusively then minimize the number of insertion directions Never require the assembly to be turned over Case I Case II Tech14x Dr Seth Bates 17 DFM and DFA Design Guidelines Joining Options parts can be joined using fasteners screws nuts and bolts rivets snap fits welds or adhesives Design to eliminate fasteners and to place them away from obstructions Tech14x Dr Seth Bates 18 DFM and DFA Design Examples Tech14x Dr Seth Bates 19 Combining to Minimize the Number of Parts To determine whether it is possible to combine neighboring parts ask yourself the following questions Must the parts move relative to each other Must the parts be electrically or thermally insulated Must the parts be made of different material Does combining the parts interfere with assembly of other parts Will servicing be adversely affected If the answer to all questions is NO you should find a way to combine the parts Tech14x Dr Seth Bates 20 Minimizing the Number of Parts Another Approach The concept of the theoretical minimum number of parts was originally proposed by Boothroyd 1982 Generally during the assembly of the product a part is required only when 1 A kinematic motion of the part is required 2 A different material is required 3 Assembly of other parts would otherwise be prevented If none of these statements are true then the parts do not need to be separate entities and may be combined Follow the KISS principal KISS Keep It Simple Stupid Tech14x Dr Seth Bates 21 End Design for Manufacturing and Assembly


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