Snap-fit design — cantilever snap (deflection, strain, mating force), annular snap (ring snap), torsional snap, permissible strain by polymer (semi-crystalline vs. amorphous), undercut geometry, mold release requirements (draft, side actions), assembly force calculation, retention force, fatigue for multiple-cycle snaps, material selection (POM, PA, PP, ABS, PC), and DuPont/Bayer design guides.
