Insert Molded Plastic Key Terms

Learn about insert molded plastic processes and equipment
By Terri Deno Insert molded plastic is a type of plastic made from the process of injection molding. The plastic material is injected into a cavity or mold and surrounds some type of an inset that is placed in the same mold before the plastic is melted. This particular molding process was originally created to encapsulate wire-plug connections inside electrical cords. There are now many uses for insert molded plastic materials such as threaded fasteners, bifurcations and other types of electrical components that need to be encapsulated.

Insert molding, overmolding

Insert molding is the process that creates insert molded plastic products. The process uses a specific mold that opens as it cools to release the finished product. Additional work, such as circuit testing or die cutting, may be needed.
Try:  Plastics Tech provides an outline of the process of insert molding.

Automatic mold

An automatic mold is a mold that can repeatedly go through the molding cycle without any assistance from an operator.
Try:  AB Plastic Injectors provides examples of semi-automatic and automatic injection molding machines that  use automatic molds.

A-side, stationary side

The A-side, or stationary side, of a mold is the half that mounts to a fixed part on the molding press. The A-side of the mold does not contain the ejector pins to make the visual side of the mold.
Try:  Protomold provides information on choosing the right A-side and B-side of the mold to get the best finished product.

Ejector pin, ejector sleeve

An ejector pin is a sleeve, blade or pin that pushes the finished material out of a mold. The pins are attached to an ejector plate that is actuated by a press or auxiliary air cylinders.
Try:  Plastics Technology describes a new system of ejection that does not use pins or sleeves. Ferris State University provides an animation of how an ejector sleeve works.

Plastic types

There are many plastic materials used in insert molding processes. The most important aspect of any plastic used in injection and insert molding is the ability to properly melt and cool with little mold shrinkage.
Try:  Custom Part provides a chart that describes the specifications of different plastic materials used in injection and insert molding processes.

Antistatic agent

An antistatic agent is an additive in the plastic. This additive is used to improve the plastic for electrical conductivity. This allows any charge used with the plastic to go to ground instead of remaining in the part.
Try:  Shanghai Jinshan Chemical provides information on antistatic agents used specifically for PE, PET and PVC plastics.