Mechanical Fastening (기계적 죔) Bolt, Nut, Thread Rivet, Staple Snap fit, Shrink fit Spring clip, Seaming Ease of assembly, disassembly. Ease of parts replacement, maintenance and repair.

Fastening

Bolt, Nut, Thread

Rivet, Staple

Snap-in, Thermal shrink

Spring clip, Seaming

Design for Assembly Design for assembly (DFA) is to simplify the product so that the cost of assembly is reduced. Comparison of Assembly Methods: Manual assembly / Fixed or hard automation / Soft automation or robotic assembly. In manual assembly, parts are transferred to workbenches where workers manually assemble the product or components of a product. Hand tools are generally used to aid the workers. Although this is the most flexible and adaptable of assembly methods, there is usually an upper limit to the production volume, and labour costs (including benefits, cases of workers compensation due to injury, overhead for maintaining a clean, healthy environment, etc.) are higher. Fixed or hard automation is characterised by custom-built machiner that assembles one and only one specific product. Obviously, this type of machinery requires a large capital investment. As production volume increases, the fraction of the capital investment compared to the total manufacturing cost decreases. Indexing tables, parts feeders, and automatic controls typify this inherently rigid assembly method. Sometimes, this kind of assembly is called "Detroit-type" assembly. Soft automation or robotic assembly incorporates the use of robotic assembly systems. This can take the form of a single robot, or a multi-station robotic assembly cell with all activities simultaneously controlled and coordinated by a PLC or computer. Although this type of assembly method can also have large capital costs, its flexbility often helps offset the expense across many different products. Graphically, the cost of different assembly methods can be displayed as in Figure 1. The non-linear cost for robotic assembly reflects the non-linear costs of robots (even small ones cost alot). The appropriate ranges for each type of assembly method are shown (approximately) in Figure 2. Assembly methods should be chosen to prevent bottlenecks in the process, as well as lower costs

Design Guidelines for Manual Assembly eliminate the need for workers to make decisions or adjustments. ensure accessibility and visibility. eliminate the need for assembly tools and gauges (i.e. prefer self-locating parts). minimise the number of different parts - use "standard" parts. minimise the number of parts. avoid or minimise part orientation during assembly (i.e. prefer symmetrical parts). prefer easily handled parts that do not tangle or nest within one another.

Design Guidelines for Hard Automation reduce the number of different components by considering does the part move relative to other parts? must the part be isolated from other parts (electrical, vibration, etc.)? must the part be separate to allow assembly (cover plates, etc.)? use self-aligning and self-locating features avoid screws/bolts use the largest and most rigid part as the assembly base and fixture. Assembly should be performed in a layered, bottom-up manner. use standard components and materials. avoid tangling or nesting parts. avoid flexible and fragile parts. avoid parts that require orientation. use parts that can be fed automatically. design parts with a low centre of gravity.

Design for Assembly