Molding Defects & Troubleshooting

What Is a Flash?

Flash is a thin, unwanted fin or skin of excess material on a molded or cast part, formed when molten plastic, rubber or metal is forced into a gap in the mold.

What Are Sink Marks? Definition, Causes & Fixes

Sink marks are shallow depressions on the surface of a molded part, usually directly opposite a thick section such as a rib, boss or wall junction.

What Is Splay in Injection Molding?

silver streaking

Splay is an injection molding defect that shows up as silvery streaks or splash-like marks on the surface of a molded part. It is caused by gas in the molten plastic, most often moisture from resin that was not dried properly, and is also known as silver streaking.

What Is Warpage? Meaning, Causes & Fixes | NICE Rapid

Warpage is the unintended distortion of a molded part, such as bowing, twisting or curling out of its designed shape, that appears once the part is released from the mold. It is caused by uneven shrinkage, usually from differences in wall thickness, uneven mold cooling or, in fiber-filled plastics, fiber orientation.

What Is a Weld Line?

knit line

A weld line, also called a knit line, is the seam that forms on a molded part where two separate flow fronts of molten plastic meet and fuse incompletely.