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Your injection-molding glossary

By Cory Arbogast on Aug 13, 2015 9:11:00 AM

Injection molding can be a complex industry to understand. However, some of the processes and terminology don’t necessarily have to be to those unfamiliar to what it is and how it’s done.

Here’s a quick glossary of some of the most commonly used terms in our industry to help you become more familiar with what we do and how we do it.


On an injection-molding machine, this component is where the resin pellets are melted before being injected into the sprue and runner system of the mold.


This refers to a protrusions on molds and/or plastic parts.


This translates to “computer-aided design.”


The moveable B Half half of the tool, this is the side where the plastic part is Ejected.  


EjectionIn order to keep the part from being scraped during ejection, a draft is a taper on the face of the part that prevents it from being parallel to the motion of the mold opening.

This is the final stage of injection molding processes, in which the part is ejected from the mold by pins or other mechanisms.

Flow Marks

Flow Marks are visible marks on the part that show where two flow fronts of plastic come together in the mold before it solidifies.


This refers to the spot where the plastic enters into the mold’s cavity. Automatically Trimmed Gates are features in the tool that break the gate when the molding tool opens to eject the new part. Manually Trimmed Gates require an operator to separate parts from runners.


Forcing liquefied resin into a mold to form a part.


The resin or plastic is the name for the chemical plastics that are injected and form the plastic part.



A groove that is cut into the molds that allows plastic to travel from the machine through the sprue through the runner and through the gate to fill the part.

Short Shot

A part not completely filled with resin, this results in missing features.


The channel that links the machine nozzle to the runner.


The portion of the part where a hand pull or slide is needed to make holes, windows or clips not already in the line of draw.


This is a deformed part of the product where the part has distorted during cooling. It is usually caused by inconsistent wall sections or uneven cooling.


These terms are some of the most commonly used ones with regard to injection molding. At Pleasant Precision, Inc., we are proud of the strong reputation we have built for our injection molding with regard to our high precision and unique success partnering with our customers.


Topics: injection molding

Author: Cory Arbogast

Copyright Pleasant Precision, Inc.