Important key terms for Plastic injection moulding

Cavity ——The concave space in the plastic injection moulding which is filled with hot plastic to create the desired part,female portion.Sometimes referred to as the "A side" of the mould,give the moulding its external form.

Core——The convex half of the plastic injection moulding,Male portion,Normally it's referred to as the "B side" of the mould.It usually forms the internal shape of the moulding.

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

Draft or Draft Angle——The defree of taper of a cold cavity sidewall or the angle of clearance designed to facilitate the ejection of the parts from the plastic mould.Generally speaking,all plastic components should be designed with draft where possible.

Sprue——The channel that connecting the runner to the nozzle of the injection moulding machine.

Gate——is a channel or orifice connecting the runner with the impression,which the hot liquid plastic enters the mould cavity.Excess plastic from the gate area can be trimmed automatically or manually once the part is ejected.

Runner——a  channel machines into the mould plate to connects the sprue with the gate to the impression(cavity).The plastic travels from the injection moulding machine through the sprue,through the runner,to the gate and into the cavities.Normally the feed system comprises a sprue,runner and gate.

Flash——is the name given to the wafer of material which escapes from the impression if the two mould halves are not completely closed.Popularly speaking,flash is the excess plastic that goes outside of the intended part moulding along a seam or plastic mould parting line and is still attached to the part.

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

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