Injection molding defects-moisture streaks/splay marks

- Mar 28, 2018-

Appearance

Usually oblong, silvery surface streaks which are open in the shapre of a U counter to the direction of flow. The material pumped out of the cylinder is foamed and shows blisters on the injection molding parts surface.

Cause

Moisture content too high; water vapor is produced during melting and this results in the surface of the molding being torn open.

Correction

1. Use material adequately predried to a residual moisture content of < 0.1 %.

2. Increase back pressure.