Undercut (molding)

Undercuts on molded parts are features that prevent the part from being directly ejected from an injection molding machine.

[1] This is an extra part of the mold that moves separately from the two halves.

[1][2] If the size of the undercut is small enough and the material is flexible enough a side action is not always required.

In these cases the undercut is stripped or snapped out of the mold.

When this is done usually a stripping plate or ring is used instead of ejector pins so that the part is not damaged.