According to principles of plastic part design in post B-1~B-4 and mold concept, designers could make feasible/ producible part and mold accordingly. However, customers nowadays have more and higher requirements regarding products, they want more fashion/ personalize/ complicated designs. While part with more complicated design (aka Undercut), mold design needs more complicated mechanisms to fulfill the same.

Let’s discuss 2 concepts before we move into the main topics,

• Opening direction: Each mold has at least one opening direction, which is the direction of mold (fix and moving side) opening. The qty. of opening direction is decided by the part design. The position/ direction/ orientation of the part in the mold corresponds the mold opening direction which decides the layout of the mold.
• Undercut: A part/ mold design that mold cannot eject part smoothly.

The purpose of Mechanism is to increase the qty. of opening direction which is different from the direction of mold opening. It creates space inside mold to release undercut, therefore, the mold could eject part smoothly. Mold with mechanism could overcome the undercut and produce parts with more complicated design.

Here discuss Lifter: undercut locates at inner area of part.

The purpose of lifter is to overcome the undercut locates at the area cannot be reached after mold opened, see example in table-1. Lifter is an additional / moving part similar to ejector pin inside mold, it attached to ejector plate and guided by the tunnel inside mold. Lifter moves inside the tunnel with a certain angle while mold ejects part (during ejector plate moves), see detail in table-2.