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Burn Marks

Burn Marks
Possible Cause Suggested Remedy
Melt temperature too high a. Decrease melt temperature
b. Lower back pressure
c. Lower screw RPM
Air entrapped in mould a. Vent cavity at final point of fill
b. Decrease first stage pressure or injection speed
c. Relocate gate
d. Clean vents and/or enlarge vents
e. Reduce clamp pressure to allow parting line vents to work
Injection rate too fast a. Decrease injection rate
b. Decrease first stage pressure
c. Decrease boost time
d. Enlarge gates
Moisture in material a. Review material handling to eliminate moisture pick up
b. Dry material prior to moulding
c. Utilize hopper dryers