Injection Molding Glossary: Glossary of Terms Used in Injection Molding

Injection Molding Glossary

Glossary of Terms Used in Injection Molding

Injection Molding Glossary
Boss: Refers to the round protrusions on plastic parts and molds
Cavity: The hollowed-out portion of a set of molds that will be used in shaping a container as it is formed on a bottle machine
Core: Refers to the side of the tool where the plastic part is injected from; also known as the bottom half of the tool
Core Outs: Refers to the portion of a part that is gutted out in order to achieve uniform wall thickness. This portion of the part has no end use function other than lightening the part and reducing warp
Draft: Refers to portion of injection molding part that has some taper to make it easier to remove from the mold. Generally all plastic components should be designed with draft where possible
Gate: The point of rubber entry into a mold cavity
Gibbs: Area of the custom injection mold that holds the slide down so the cam can actuate it
Hand Load: Aluminum or steel feature in a mold used to create undercuts in molded parts. They are manually removed from the mold during the part ejection process
Heel: Refers to the portion of an automatic custom injection mold that keeps the slide in the forward position when the molding machine is closed on the mold
Horn Pin: Pin used to actuate the slide on an automatic injection mold
Line of Draw: The direction in which the two custom injection mold halves will separate from the plastic part allowing it to be ejected without any obstructions from metal creating undercuts
Ribs: Refers to thin bladed features on a part that are used for strengthening wall sections and bosses. Also, used to minimize warp
Runner: The distribution system within a mold; connects the Sprue to the Gates
Shear: Refers to when plastic enters into the mold and the melt is maintained by friction produced by speed and pressure. Too much shear can cause the plastic material to burn, too little can cause the material to freeze off causing short shot
Short Shot: The result of a plastic part not filling completely, including some or all of the details
Shrink Rate: Refers to how much the plastic material will shrink after cooled. This % of shrink 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. Although most fall in between .004″ and .021″
Side Action: Term used for slides and/or hand pulls used in the injection mold build process
Sink Marks: Refers to areas of the molded part where it seems to be sunk in, due to un-uniformed wall sections, thick wall sections and rib/boss to thickness ratios being off
Slide: Area of the custom plastic injection molds that is used for creating undercuts. Required for automatic injection molds
Sprue: The initial entry point of rubber into a mold. In a simple mold, it is the same as a gate
Steel Safe: Refers to the amount of metal left on the mold in order to tweak in a dimension. For example, if you have an inside diameter that is supposed to be .500 you may leave the mold at .505 in case you get excessive shrink
Thin Wall Molding: The molding of plastic parts with wall thicknesses .005″ to .060″ thick
Undercuts: Refers 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
Vestige: Material protruding from the gate area after gate runner has been removed from the injection molded part. This vestige is usually trimmed by the molding machine operator
Wall Thickness: Refers to how thick the cross section of the plastic part is
Warp: Refers to area of a injection molded part that distorts during cooling or molding, causing undesired results in the finished product. Usually caused by un-uniform wall sections