Design guidelines for robust snap fits

Abstract

Snap fits are widely used to join vehicle components. Simple to use, they typically require that one part be pressed against another. Snap fits are usually made of plastics, which is inherently prone to size and shape variation. Hence, it is important for a snap fit to be robust, i.e., it must "perform" satisfactorily under random variation in material and geometry. In this paper, two sets of design guidelines are developed to improve the robustness of snap fits. A general set of guidelines can be used to determine the distribution of teeth, joint stiffness and interference. A more specific set can be used to determine more detailed design features, such as lead angle, width and length of a snap fit. An example shows how these design guidelines are used.