Honeywell Plastics Snap-Fit Design Manual

Why use snap-fits? This chapter will give you a thumbnail sketch of the benefits of snap-fits and the materials used to make them. Snap-fits are the simplest, quickest and most costeffective method of assembling two parts. When designed properly, parts with snap-fits can be assembled and disassembled numerous times without any adverse effect on the assembly.

Snap-fits are also the most environmentally friendly form of assembly because of their ease of disassembly, making components of different materials easy to recycle. Although snap-fits can be designed with many materials, the ideal material is thermoplastic because of its high flexibility and its ability to be easily and inexpensively molded into complex geometries. Other advantages include its relatively high elongation, low coefficient of friction, and sufficient strength and rigidity to meet the requirements of most applications.

The designer should be aware that the assembly may have some “play”due to tolerance stack-up of the two mating parts. Some snap-fits can also increase the cost of an injection molding tool due to the need for slides in the mold. An experienced designer can often eliminate the need for slides by adding a slot in the wall directly below the undercut or by placing the snaps on the edge of the part, so they face outward.