| Possible Cause |
Possible Solution |
| Material is oriented during injection. |
Decrease injection velocity for slower filling.
Increase mold temperature.
Adjust velocity profile to provide
homogeneous melt. |
| There is a difference in packing density. |
Increase hold pressure.
Increase injection fill speed to fill faster.
Increase screw RPM. |
| Molded part has stresses. |
Increase melt temp.
Prevent overpacking at gate by reducing
hold pressure or reducing hold time.
Lengthen cooling time.
Delay knockout actuation.
Increase injection forward time.
Reduce temperature differential in mold. |
| Material flow into mold is not uniform. |
With multi-cavity molds, make sure
flow is balanced. |
| Part is to hot when it's ejected. |
Reduce mold temperature.
Increase cooling time.
Reduce melt temperature. |
| Knockout is operating improperly. |
Knockout engaging too fast, slow down
ejection.
Non-uniform operation of pins.
Bearing area of knockout pins is too small.
Increase diameter and number of knockout pins.
Relocate knockout pins to strong area of part.
With delicate parts, change to air blow-off. |
| Part design is incorrect. |
Make sure part contains no sharp variations
in cross sections.
Correct taper or draft insufficiencies |
