Snap Joint

A snap joint is economical in two respects it allows the structural member to be molded simultaneously with the molded product, and it allows rationalizing the assembly, compared with such other joining processes as screws. Table 3-4 provides a comparison of its advantages and disadvantages. Some examples of the various types and their design considerations are shown in Figs. 3-23 to 3-25. 

The geometry for snap joints should be chosen in such a manner that excessive increases in stress do not occur (Table 4-3). The arrangement of the undercut should be chosen in such a manner that deformations of the molded product from shrinkage, distortion, unilateral heating, and loading do not 

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Effects of processing on the properties of the snap joints (orientation of the molecules and of the filler, distribution of the filler, binding seams, shrinkage, surface, roughness and structure)... 

Difficulties with a continuous loading of the snap joint... 

Snap fits are widely used for both temporary and permanent assemblies, principally in injection and blow molded products. Besides being simple and inexpensive, snap fits have superior qualities. Snap fits can be applied to any combination of materials, such as plastic and plastic, metal and plastics, glass and plastics, and others. All types of plastics can be used (Chapter 3, DESIGN CONCEPT, Snap Joint). 

Figure 13.19 Snap joint An integral cantilever spring at maximum deflection on insertion, compared with the undeformed shape, and principal tensile strain contours (%).

Table 5-4. Mobay Guide Data for Permissible Short-Term Strain in Snap Joints...

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