Plastic Injection Molding Key Terms

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Plastic Injection Molding Key Terms

10 Key Terms for Plastic Injection Molding

Our customer base has a very diverse level of knowledge when it comes to plastic injection molding. We have large companies with seasoned pros who give us a lot of repeat business, all the way down to inventors who have an idea for a new product they want to market, and this is the first time they are working with a plastic injection molding company.

Regardless of your level of knowledge, there are certain plastic injection molding key terms you should know in order to communicate with our engineers through the process of turning your idea into the next “better mouse trap.” This is the short list, but for more plastic injection molding term definitions, please visit our Injection Molding Glossary.

Cavity – The concave space in the mold which is filled with hot plastic to create the desired part. Sometimes referred to as the “A side” of the mold, it usually forms the outer surface of the molded part.

Core – Also referred to as the “B side” of the mold, the convex half of the mold that usually forms the inner surface of the part.

Draft or Draft Angle – The degree of taper of a cold cavity sidewall or the angle of clearance designed to facilitate the ejection of the parts from the mold. Generally all plastic components should be designed with draft where possible.

Flash – Excess plastic that goes outside of the intended part molding along a seam or mold parting line and is still attached to the part.

Gate – An orifice through which the hot liquid plastic enters the mold cavity. Excess plastic from the gate area (vestige) can be trimmed manually or automatically once the part is ejected.

Line of Draw – The point at which the two molding halves separate to reveal the injection molded part. This allows the part to be ejected without damage from metal obstructions. On a finished part, the parting line shows where the two mold halves met when they were closed.

Runner – The channel that connects the sprue with the gate. The plastic travels from the injection molding machine through the sprue, through the runner, to the gate and into the cavities.

Shrink Rate – Ranging from 0.001-0.060 per inch, the rate at which the injected plastic will shrink once it is cooled.

Sprue – The canal connecting the runner to the nozzle of the injection molding machine.

Warp – Dimensional distortion in the injection molded part, often caused by internal stresses via uneven material flow, cooling and compression.

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