ME3101 / ME3102Mechanical Systems DesignChapter 6Basic Design for Assembly
DFA – Design for AssemblyIn the previous chapter, we havetalked about DFM, Design forManufacturing.In this chapter, we will go throughDFA, Design for Assembly.Similarly, DFA occurs through theentire design process, from the start,till actual production
DFA – Design for Assembly Generally accepted guidelines for DFA: •Minimize number of parts •Feature lesser assembly movements •Provide Self Aligning features •Eliminate visual obstructions to assembly •Reduce number of tools required •Use symmetrical parts
Minimize number of partsSimilar to DFM, a reduction in number of parts is a rule ofthumb to follow for Design for assembly.Lesser parts = Lesser steps required for assemblyWe will illustrate this concept in the next slide.
Minimize number of parts Extracted from: http://www.cbpa.ewu.edu/~pnemetzmills/OMch3/omfac.html
Lesser assembly movementsTo reduce assembly time,designers can take intoconsideration a “top-downapproach to design” and havefeatures in the same orientation.This reduces the need to re-orientate the main body duringassembly.
Provide Self Aligning FeaturesCompare the 2 diagrams below.The design on the left requires more effort to align the parts together.The design on the right however, has a self aligning feature that allowsthe part to fit together easily, thus reducing assembly time No self aligning feature Integrated self aligning feature
Eliminate Visual Obstructions Look at the 2 diagrams on the left. As a designer, take note to prevent visual obstruction of assembly features. Blocking visual sight of assembly features increases the difficulty in assembly and thus increases time required.
Reduce Number of Tools RequiredAnother simply rule of thumb fordesigners to follow is to reduce thenumber of tool variants required.For example, the same kind offasteners can be used to reduce thenumber of tools required to fastenthem.
Use Symmetrical Parts Whenever possible, part designs should feature symmetry to reduce time spent on alignment during assembly. However, where symmetry is not possible to attain, obvious asymmetry is preferred for easy identification ofDesign for symmetry the correct alignment Obvious Assymmetry
In conclusion…Designers should always take intoconsideration the practicality of theirproduct.While the product has to be usable andefficient, it has to be able:•to be manufactured (DFM)•to be assembled efficiently (DFA)