An undercut is an indentation or projection on a workpiece usually means that the core moving direction is not parallel to the draw direction of mold, so that the molded workpiece makes ejection from the simple two-part mold almost impossible. Because of the movement way they are oriented, some feature is introduced to injection mold deisgn. The cores or protrusions, which used to form these indentation, referred to as undercuts, are typically used in articles such as enclosures to provide a snap fit to assemble workpieces.
Internal undercuts can be molded by using two separate core pins, as shown in Fig2.29. This is a very practical method to use, but flash will sometimes occur where the two core pins meet.
