: injection troubleshooter :
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• Pitting - plastic injection troubleshooter
• Description:
Pitting is the presence of unmelted particles due to difficult dispersion of additives, wrong mixing or crosslinking during processing.
• Causes:
machine
· wrong or worn out screw, giving hang-ups
· melt temperature too low
· injection pressure too low
mould
· shear in gating
· sharp corners
material
· inhomogeneous material
· contamination
• Actions:
1st
get shear down
2nd
lower back pressure
3rd
decrease injection speed
4th
change temperature profile
5th
check regrind percentage
6th
check shot size vs part
7th
check hot-runner: torpedoes
contact:
jmfalcao@moldplast.com
