Injection Molding Glossary
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Co-molding
Co-molding is one of overmolding. It refers two plastic materials to bond, which usually are a hard material like ABS and a soft material like TPE. Co-molding provides aesthetically pleasing color contrasts.
Core Out
Core out refers to is a technique where you remove material from a plastic part, leaving distinct walls and ribs which provide enough strength and mating surfaces for other parts in the assembly.
Draft
Also known as “draft angles”. Refers to portion of injection molding part that has some taper to make it easier to remove from the mold. Generally all plastic components should be designed with draft where possible.
Ejector Pins Marks
Marks left by ejector pins. Ejector pins are long pins that are used in the injection molds to push the final molded product out of the mold. The marks can not be removed due to process of injection molding.
Flashing
Flashing is also known as flash. It refers to plastics that leaks into a fine gap in the parting lines of the mold to create an undesired thin layer.
Gate
Gate is also known as gate location. It refers to where the plastic enters into the cavity of the mold. It plays a role of the link between the part and the runner system.
Insert molding
Insert molding involves molding plastic around a core or “insert”. Most often, the insert is a metal object, such as a pin, blade, threaded rod, electrical contact, wire, and others.
Parting line
A parting line is the “line” or “seam” of separation on the part where the two halves of the mold meet, and it can not be avoided.
Ribs
Rib refer to thin bladed features on a part that are used for strengthening wall sections and bosses. It helps to eliminate sink marks and minimize warp.
Sink marks
Sink marks are also know as shrink marks; Refers to areas of the molded part where it seems to be sunk in.
Warpage
Warp (warpage) is also know as bending. It refers to area of a injection molded part that distorts or bends during cooling or molding.
Weld lines
Weld lines are also known as “stitch lines” or “knit lines”. These are imperfections in the part where separated flows of cooling material meet and rejoin, often resulting in a visible line.
Undercuts
An undercut is any indentation or protrusion that prohibits an ejection of a part from a one-piece mold. Undercuts add cost to tooling and molding, which is recommended to eliminate or minimize as possible.