Draft Angle for Plastic Injection Molding
May 22, 2020

A draft angle is a slant that is applied to every side of most areas of an injection molded part. The angle, which is positioned to run toward the direction of a mold’s pull and parting line, helps demold the part from the mold cavity.

When developing parts for plastic injection molding, no draft is designed into the part, it may run the risk of poor cosmetic finishes during part cools, such as scratches, etc. These issues can damage not only part but also mold in extreme cases. Since plastic shrinks as it cools, portions of the part may pull away from the mold while others grip the core. If there is no draft angle that allows a simple push from the ejector pins to pop the part out of the mold, the part’s surfaces will often drag along the mold as it is being ejected.

By adding draft angles to molding design, it can avoid these risks and lower the cost of production. Draft will allow parts to release from the mold with ease, which will result in better cosmetic finishes and fewer rejected parts.

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