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Ryton® PPS plus Xtel® PPS Alloys > Ryton® PPS Technical Library > Ryton® PPS Design Guide > Snap Fits and Interference Fits 
Design Guide

Snap Fits and Interference Fits

The high strength and modulus of Ryton® PPS compounds make them suitable for snap fits and interference fits. Because of the high modulus, very little flexure or ductility is to be expected, but studies have shown that adequate holding strength can be achieved with minimal interference. Due to the rigidity, considerable force is often required for assembly, and the force must applied with care to prevent part cracking.

Snap Fit

The most convenient method of assembling plastic parts is the snap fit. The savings in assembly costs can more than offset the increase in tooling costs required by this technique. Studies have shown that the high strength and rigidity of Ryton® PPS compounds provide good holding strength with a minimum of flex and interference. The diagram below details the guidelines for the design of snap fit members for different Ryton® PPS compounds and Xtel® PPS-based alloys. Typically, Ryton® PPS snap fit applications involve only one time assembly.

   

 

 
Interference Fit

The strength and modulus of Ryton® PPS compounds makes them suitable for retention of interference fit components, however molded-in inserts are generally preferred especially for larger components such as hubs or bearings. To prevent cracking, the degree of interference should typically not induce more than about 0.5% hoop strain. Tests have shown that increasing depth of insertion (or increasing the area of surface contact) can be more effective at improving pull out force than increasing interference.