Plastic Injection Glossary


The negative side of the mold, sometimes called the cavity, which often forms the exterior of the plastic part.


The process of gradually cooling a plastic part after it has been heated to a temperature just below its softening point, making the material tougher.


Joining completed molded parts together to form a final product.

Back To Top

Sometimes referred to as the core, this is the side of the mold containing the injectors; most often forms the interior of the plastic part.


The section of the molding machine containing the screw which melts resin pellets and injects the compressed material into the runner of the mold.


A protrusion on a plastic part or mold used to add strength to the piece or create alignment for fasteners. 


Gas pockets or vacuum voids which occasionally occur inside plastic during the injection molding process.

Back To Top
Acronym for Computer Aided Design
The negative shape formed in a steel tool in which plastic is injected to create the mold.
A portioned out amount of material loaded by the screw into the mold during a single cycle.
The process of hardening of injection molded parts.
The time is takes for the plastic injection process to complete. One plastic part can sometimes take multiple cycles to complete.
Back To Top
The degree of taper a side wall has to facilitate removal of plastic parts from a mold.
A measure of the hardness and resistance to marring in a material.
Back To Top
EDM (Electric Discharge Machining)
A type of precision machining process used to build tools for plastic injection molding; utilizes electrical charges to erode metal.
Ejector Pin
A pin used to push the plastic molding out of its cavity or mold.
Acronym for Enterprise Resource Planning; a software dedicated to managing manufacturing processes and automating administrative functions for greater efficiency.
Back To Top

The final surface texture of a part.

Back To Top

The opening in the mold where the molten plastic is injected into the final part.

Back To Top
The level of resistance a plastic material has to compression or surface damage.
Hot-Runner Mold
Heated molds that melt plastic and send it to nozzles which fill the plastic part cavities. 
Hot Stamping
An engraving process where a heated die is used to apply pressure to the plastic part, transferring pigment onto it.
Back To Top
Injection Molding
A manufacturing process where melted plastic is injected into a negative of the part being produced, known as a mold cavity. After the plastic cools, it becomes a solid of the positive component.
Back To Top
Apparatus which holds and guides the tool during the plastic injection machining process.
Back To Top
Molding Material
Types of plastic material used in injection molding. These materials can comprise of resin, filler, pigments, plasticizers, or other ingredients.   
Mold Release
A material used to prepare a part’s surface for easier ejection of a mold.
Back To Top
The hollow nose attached to the end of the injection machine which transfers melted plastic into the mold.
Back To Top
Pad Printing
The process where ink is taken from an etched design and deposited on a molded plastic part to create a design.
Parting Line

A line formed on the seam of the part where two molds meet.

A polymeric material which can be melted under heat and pressure.
A certain material incorporated in melted plastic to increase its flexibility when hardened.
Cleaning one type of material out of the cylinder of an injection molding machine by forcing it out with new material.
Back To Top
Generic term for a chemical compound injected in to a mold.
The channel that connects the sprue and nozzle to the gate of the mold cavity.
Residence Time
Duration of time an injected material charge sits in the heating cylinder before its injection into the mold
Back To Top
A device housed in a barrel which portions out resin pellets and melts them on before they are injected into the mold.
A single complete cycle of the screw in the barrel of the molding machine.
Shrink Rate
The amount of shrinkage that occurs during plastic cooling (Usually between .004” and .20”)
Opening feed that sends material from the nozzle to the runner.
Back To Top
A recyclable polymeric material that can be heated and cooled repeatedly without changing the structure of the plastic.
The solid mold in which resin is injected to for the plastic part.
Back To Top
Ultrasonic Welding
A process of welding that produces a molecular bond between compatible thermoplastic parts.
Back To Top
For over 40 years, Retlaw has produced quality injection molding tools which has led us into thermoplastic injection molding for a wide variety of industries. With over 19 injection molding machines, decades of collective experience, and over 50,000 square feet under roof and room to expand, we are always ready for your new projects.
Learn More
Let’s get together and build a solution.