AIM Processing Small Plastic Parts Blog

Like most technical specializations, plastic injection molding has a vocabulary all its own. In some cases the terms are unique, in others they may be common terms but used in a unique way in our industry. All in all, there are probably hundreds of words in the plastic injection molding lexicon.

You certainly don’t need to know them all, but if you are considering a plastic injection molding project, here is a quick trip through the alphabet for a handful of key terms to give you a little familiarity with our industry.

Annealing — The heating of a plastic part for a specified time period, and subsequent cooling, to relieve internal stresses. (Careful! Inaccurate cooling processes can create negative results.)

Barrel — The section of a molding device where resin is heated and mixed.

Charge — The amount of viscous plastic need to fill a mold.   

Degassing — Briefly opening then closing a mold to let air or gas escape.

Elastic Memory — The tendency of some plastics to revert to a previous shape.

Flash — Excess material sometimes found along a seam.  

Gate — The opening through which viscous plastic is forced into a cavity.   

Hardener — A substance added during the molding process to affect the way the plastic dures.

Impact Resistance — A plastic’s ability to avoid breaking when struck.  

Jig — A device for holding parts or tools.  

Knockout Pin — A small rod that ejects a part from the mold.  

Low Temperature Flexibility — The characteristic of a plastic allowing it to bend without breaking at reduced temperatures.

Mold — The form into which viscous plastic is injected and that gives the part its finished shape.

Nozzle — The hollow metal hose through which viscous plastic is injected into the mold.

Orange Peel — A typically undesirable surface finish of a part that is rough or dotted.

Parting Line — A mark on a finished part created where the two halves of a mold came together.  

Resin — The basic material for plastics.  

Scrap — Unusable hardened plastic remaining at the end of a molding process.   

Thermoplastic — A type of plastic that can be repeatedly softened by heat and hardened by cooling. 

Uniform Cooling Time — The same cooling time throughout a part, which is ideal for avoiding warping.  

Viscosity — Resistance to flow of a liquid.  

Weld Line — A visible line on a finished part created under certain conditions that can weaken the part.  

Yield Point — The first point on the stress-strain curve at which greater strain does not cause greater stress.

There you have it… Plastic injection molding A to Z, minus the Z, Q, and X, as there aren’t any key terms there! As always, let us know if you have questions or want to discuss a plastic injection molding project.