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A-Z List of Injection Molding Terms

Posted in News & Updates

Since each molding press is different, it is important to know the coinciding terms. Here is an alphabetic list of common injection molding terms:

Annealing: process of heating and cooling a part to release internal stresses

Barrel: component of the press where resin is mixed and heated

Cavity: the outline of the designated shape of the molded part

Degassing: allowing gas to escape by quickly opening and closing the mold, preventing any bubbles from forming

Deflashing: process of removing the thin layer of plastic that flows outside of the cavity where the two halves of the mold meet. Typically this is completed by cutting or grinding each unit.

Ejection Pin: small metal rods to push parts out of the mold

Flash: extra material at the seam of a molded piece

Gate: an opening for the melted resin to seep into the mold

Hot-Runner Mold: when two plates are heated and folded together, allowing the melted resin to flow into the cavity through the nozzle

Injection Molding: resin is liquefied and injected into the cavity of the mold to form the part

Jig: the mechanism that holds tools

Knockout pin: a small pin that pushes the molded part out of the cavity

Low Temperature Flexibility: a characteristic which permits a specific plastic to bend without breaking

Machine Shot Capacity: maximum amount of resin that can be injected in a single shot

Nozzle: the hollow metal nose attached to the end of the barrel where the resin is injected into the cavity

Overmold: most commonly used to mold soft elastomers to rigid plastics, i.e. over molding a hub onto a shaft

Purging: cleaning the molding machine of any remaining scrap before using the machine again

Resin: the plastic material

Shot Size: maximum capacity of resin that can be injected in a single shot

Thermoplastic: a material that can be softened by repeatedly heating and hardened by cooling

Undercut: indentation or protrusion on the molded part. Reducing undercut will reduce tooling cost.

Vent: an area that releases air as resin is flowing into the cavity to prevent bubbles or defects from developing

Weld (Parting) Line: a small line on the finished mold which is a weak spot as a result of the two flow fronts joining together during the molding process

Yield: the number of defect-free products that are able to be produced


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