Snapfit

Snapfit is a family of joints used to assemble two plastic components without separate fasteners by using compliant, or flexible, features that snap into engagement with a mating feature. The joints rely on bending or torsional deflection of a designed section to create a secure hold through friction and, in some cases, an interference fit. Snapfits are common in consumer electronics housings, automotive interiors, appliances, and packaging.

There are several common snap-fit configurations. Cantilever snap-fits use a flexible beam that deflects as a mating feature is inserted and then returns to engage a hook or barb. Annular or ring snap-fits constrain a circular feature by a flexible undercut or groove. Torsion or hinge-type snap-fits use curved flexural elements that rotate to lock parts together. Some designs combine locking and guiding features to improve alignment and retention.

Materials and manufacturing play a major role. Snapfits are typically made in thermoplastics such as ABS, polycarbonate, polystyrene, polyamide, or polypropylene, and may be produced by injection molding or overmolding. Surface finish, wall thickness, and draft angles influence deflection and cycle life. Proper molding tolerances are essential to ensure reliable engagement and release without damage.

Advantages of snapfits include fast, low-cost assembly, no separate fasteners, and potential for disassembly for recycling or repair. Limitations include sensitivity to temperature and creep, limited load-bearing capacity, and potential wear or fatigue after repeated cycling. Design considerations emphasize adequate deflection, appropriate radii, avoidance of sharp corners, relief features for assembly, and compatibility with material properties.