10 Injection Molding Terms Mold Techs Use Daily

Injection Molding terms GreenLeaf Industries

Learn the Plastic Injection Molding “lingo” to better communicate with engineers, project managers and mold technicians.

It is our pleasure to produce the annual guide to over 200 injection molding industry terms. Download the entire ebook here.

To be fair, that’s a lot of words to learn, so we asked our mold techs to select 10 of the most common. Learn these first and you will be well on your way!

BURN – When the air temperature inside the mold exceeds the flash point of the plastic, a “burn mark” is made. If something is “burned” in molding, it shows evidence of thermal decomposition through some discoloration, distortion and localized destruction of the surface of the plastic.

EJECTOR CONFIRMATION SWITCH – A switch used to prevent mold damage by detecting if the ejector plate does not fully return to home position.

FLASH – Extra plastic attached to a molded part along the parting line or other shut-off locations in the mold.

GUIDE PINS – Devices that maintain proper alignment of the core and cavity while the mold closes. These are also called “leader pins.”

JETTING – A turbulent flow of resin from an undersized gate, or thin section, into a thicker mold section. This is opposed to a laminar flow of material progressing radially from a gate to the extremities of the cavity.

KNIT LINE – A mark on a molded piece made by the meeting of two flow fronts during molding. It can also be called a “weld line.”

NOZZLE TIP (REMOVABLE) – A replaceable tip that installs into the end of the molding machine’s nozzle. Nozzle tips must be matched to the mold surface (for sealing off high injection pressures), and to the orifice of the mold sprue.

PLASTICIZE – To soften a material and make it plastic or moldable either by means of a plasticizer or the application of heat.

PURGING – Cleaning one color or type of material from the cylinder of an injection molding machine by forcing it out with a “purge compound,” or with the new color/material to be used in subsequent production.

SHORT SHOT – A molded part produced when the mold has not been filled completely.

Next up are 10 terms that aren’t as common, but you should know them anyway!

About GreenLeaf: GreenLeaf Industries is an ISO 9001 registered manufacturer that consistently adheres to all its standards to provide our clients with consistent, reliable, quality automotive and industrial plastic parts. We are an American injection molding company, unafraid to compete in the world market and determined to succeed. Established in 1999, we take pride in our high-quality craftsmanship and superior customer service. Visit us:

GreenLeaf Industries
310 Bussell Ferry Road
Lenoir City, TN 37771
(865) 988-5661