Design for Assembly
http://www.youtube.com/watch?v=D4MnTHrMAtY
Table 14.1 lists DFA guidelines, adapted from several sources such as Andreasen, Baldwin, Digital, Huthwaite, Iredale, and Xerox. If a concept is compatible with these guidelines, one can be reasonably assured that the design will fare well in the subsequent more detailed analysis.
System Guidelines
The first guidelines reduce the number of parts through functional modularity (Figure 14.3) as discussed in Chapter 9. Examine each part, and ask how the part function can instead be completed by a neighboring part. One might also be able to fabricate several parts as one part by using other fabrication processes, such as sheet-metal forming or plastic injection molding (force-flow analysis, Chapter 6).
The second guideline is to reduce the number of parts through assembly modularity as discussed in Chapter 9. Here, several difficult to manipulate parts are bundled together onto a feature such as a board that is easy to manipulate and assemble. Several side benefits are also gained through subsystem modularity. For example, assembly modularity can help reduce defects, as it makes quality problem identification easier when one can test subassemblies rather than having to diagnose the whole product.
The third guideline suggests that one should design a product so that it is assembled outwardly. Do not design a product that requires parts to be fastened on the inside of an enclosure. This makes assembly possible with no reorientations and without having to cram one's hands or tools into tight spaces.
The fourth guideline suggests designing parts so that they are easily oriented. Parts should have self-locating features so that precise alignment by the assembly process is not required. If not that, colored tick marks or indents make orientation easier. This is especially true on electrical components, where one way pin patterns or pin identification labels should be used.
The fifth guideline suggests reducing the variety of parts. In particular, using the same commodity items such as fasteners can avoid errors. It also increases the economies of scale for the part.
Handling Guidelines
https://vimeo.com/128633876
All parts must be handled to be assembled. Handling includes picking the part up from a feed location, conveying it to a location for assembly insertion, and orienting the part for the assembly insertion. Some parts are difficult to handle; for example, springs and wires are hard to handle. Guidelines can be developed to help simplify this handling aspect of the assembly process as shown in Figure 14.4.
The first guideline suggests maximizing part symmetry to make orientation unnecessary. If one cannot make parts symmetric, then force the asymmetry to have an obvious asymmetry-plainly mark the orienting features.
The second guideline suggests augmenting asymmetries such that they can be easily oriented. Specifically for automated assembly equipment, often this can be done with the aid of gravity, though gravity does not help orienting parts manually.
The third guideline suggests designing parts so they do not tangle or stick together. Scrutinize the tangle-prone feature, and change it so that it does not tangle. Similarly, parts that are difficult to handle should be changed to make them easier to handle. Slippery or messy parts should have handling features designed in.
The fourth guideline suggests distinguishing different parts that are shaped similarly through non geometric means. One should color code or mark different thickness shims, for example, to ease identification. The fifth guideline suggests avoiding parts that nest. Nesting is when parts that are stacked on top of one another clamp to one another, such as with vacuum formed plastic coffee lids or cups found in convenience stores. One can design in features to prevent the nesting. The sixth guideline suggests designing parts with orienting features so that one can align the asymmetries inherent in the part. Often the asymmetric aspects of a part do not necessarily provide a means for alignment.