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Plastic injection molding terminology

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Injection Molding Definitions and Terminology
• Cavity
• Core
• Number of cavity
• Gate
• Sprue
• Part
• Tooling
• Slider
• Runner
• Ejector Pin
• Shrinkage Rate
• Undercuts
• Piece Price
• Draft-Angle
• Parting-face
• Sink Marks
• Warp
• Ribs
• Boss
• Wall Thickness
• Thin Wall Molding
• Short Shot
• Piece price
• Operator
• Reverse Engineering

Cavity
This refers to the upper half of the injection mold, usually for molding the outer surface of the finished product. It is mainly concave. There are not as many standing core outs on this side of the tool. Therefore, the part will generally not stick to it when the injection molding machine opens the mold.

Core
This refers to the side of the tool that the plastic part will stick to and is ejected from, also refer to the bottom half of the tool.

Number of cavities
This refers to how many pieces of part can get in one shot, for example,1 cavity means you get this item 1 piece on each shot, but it usually depends on the volume.

Gate
This is the location where the plastic gets into the cavity of the mold. Types of gates include direct gate, submarine, tunnel, edge, fan, cashew, pin-point, horn gate, and hot runner valve gate.

Sprue
The Sprue is perpendicular to the runner and is the channel that links the injection molding machine nozzle to the runner.

Part
Refers to the customer’s custom plastic parts to be made.

Tooling
Refers to the injection mold that is created to make plastic parts in the molding process.

Slider
A portion of custom plastic injection molds that is used for creating undercuts. Required for automatic injection molds.

Runner
A channel cut into custom injection molds in which plastic flows from the injection molding machine, through the sprue, through the runner and then through the gate, ultimately filling the part.

Ejector Pins
Ejector Pins are used to pushing the part off of the core half of the injection molds.

Shrinkage Rate
This refers to how much the plastic material will shrink after cooled. The shrink rate of the plastic is added to the part before the mold is designed. Every plastic material has its own shrink rate ranging from .001 per inch to as much as .060 per inch. Most shrinkage rates fall in between .004 and .021. so, our sales engineer used to communicate with you on the before the mould design.

Undercuts
Referring to the portion of the designed component where a slide or hand pull is required to create holes, windows or clips that are not in the line of draw.

Piece Price
This refers to the cost of each plastic part as produced in the injection molding process.

Draft-Angle
This refers to the portion of the injection molded part that has a taper or angle on the sidewall. Designers should incorporate a draft of all plastic parts. See here for tips.

Parting-face
Refers to the contact part of the mold on closed state and is also the dividing surface for divides the mold to be a different part.
It is one of the key factors for a mold design successful.

Sink Marks
Refers to areas of the molded part where the plastic sinks below the surface due to un-uniform wall sections, thick wall sections and rib/boss to thickness ratios being off.

Warp
This refers to the area of an injection molded part that distorts during cooling or molding, causing undesired results in the finished product. Usually caused by un-uniform wall sections. SeeFig.5 for prevention.

Ribs
Refers to thin bladed features on a part that are used for strengthening wall sections and bosses. Also, used to minimize warp.

Boss
Refers to round protrusions on plastic parts and molds.

Wall Thickness
This refers to the thickness of the cross-section of the plastic part.

Short Shot
It is the result of a plastic part not filling completely during the injection molding process, including some or all of the details.

Piece Price
This refers to the cost of each plastic part as produced in the injection molding process.

Thin Wall Molding
Thin wall molding is the molding of plastic parts with wall thicknesses .005 to .060.

Operator
A person used to run a plastic injection molding machine.

Reverse Engineering
This refers to the process of taking an existing plastic part and creating a 3D solid model for duplicating in the injection molding process. Sometimes the design may include custom changes from the OEM

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