The plastic moulding has sections missing, usually in regions remote from the injection point or in thin-walled regions, because the mould was not completely filled.
Common causes are the metered shot size is too small, the non-return valve is leaking or the injection pressure is set too low.
If the machine is running on maximum fill pressure, then the pressure drop through the feed system and cavity could be too high.
1. Increase the shot volume.
2. Switch over later from injection pressure to hold pressure.
3. Increase the temperature of the melt and mould.
4. Increase the temperature of the melt and mould.
5. Improve venting at the end of the flow path.
6. Choose an easier flowing material.
7. Increase the gate size.
8. Check the actual wall thickness of the cavity.
9. Move the position of the gate.
10. Incorporate flow leaders to reduce pressure.
11. Check for balanced filling.