Injection Mould

Like any profession, terminology for the injection mould, or injection mold (US) industries is unique. Interestingly, the terms don’t vary much from region to region.

This “glossary” should give you a reference for finding out what some of these things mean. When you’re in a meeting you can’t very well be asking what appears to be uninformed questions.

It is arranged in two categories: plastic injection molding and injection moldmaking. Many of the terms apply to both areas, after all you need a mold to do molding an what good is an injection mold without a plastic molder?

Plastic injection moldmaking terms

EDM terms

  • Burning: machining with an EDM machine, the actual operation of removing metal with the electrode. It’s burning because you can see zillions of sparks under the oil when it is machining.

  • Overburn: the distance that the sparks reach when they leave the electrode until they penetrate the steel workpiece. Usually this is from .002 to .015 inch. This is important because it controls much of the accuracy and finish of the detail produced. Can also be called spark gap or overcut.

  • zit: usually a small pit in the steel of a mold. Officially called a DC arc. Zits are bad because they are a flaw in the surface finish and will leave a “tit” on the plastic part.

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