The burn marks in plastic injection molding are that the gas in the cavity cannot be removed in time, resulting in blackening at the end of the flow.
Causes:
(1) The air in the cavity cannot be removed in time.
(2) Material degradation: overhigh melt temperature; overcast screw speed; improper design of the runner system
Remedies:
Mold design:
(1) Add an exhaust system to a place where the exhaust gas is easily generated
(2) Increase the size of the runner system
Process:
(1) Reduce the injection pressure and speed
(2) Reduce the barrel temperature
(3) Check if the heater and thermocouple are working properly.
