Undercut damage occurs when the part must deform around a feature during release and the required strain exceeds what the polymer can recover. The result may be a tear, white mark, permanent flare, or local loss of dimension.
Material flexibility, wall thickness, undercut depth, edge radius, demolding temperature, and release speed determine whether a flexible release is feasible. The same undercut can release successfully in a soft elastomeric sheet and fail in a rigid transparent material.
Corrective action
The release path should be analyzed as a deformation, not only as a dimensional clearance. Split or retractable tooling is required when elastic release is not reliable. If controlled flex is intended, the part must be supported and the strain proven through production-temperature trials.
Demolding hotter may reduce force but increase distortion and residual stress. The acceptable release window should be established from both cosmetic and dimensional results.