A part may stick through friction, adhesion, shrinkage, vacuum lock, or mechanical interference. These mechanisms look similar to the operator but require different corrections.
A hot part can drag on the tool because it lacks stiffness. A cooled part may grip a positive mold more tightly as it shrinks. Roughness and contamination raise friction. A polished sealed surface can create vacuum lock, while an undercut physically prevents release.
Identify the mechanism
Scuff direction, release timing, eject response, and the effect of breaking the seal should be observed. If a small air path releases the part immediately, vacuum lock is likely. If the part remains trapped after the seal is broken, draft, shrinkage, or undercut should be examined.
Release agents may support development or low-volume tooling, but repeated application should not replace proper geometry, surface condition, and temperature control. The correction must address the actual holding force.