Injection Molding
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ABS burnt (trapped air burn marks)
Problem Phenomenon
Black/brown burn marks appear at the end of the cavity, rib ends, or weld lines, possibly accompanied by odor.
Cause Analysis
During filling, the air in the cavity is compressed and cannot be discharged, producing the diesel effect that burns the plastic at high temperature; blocked vent grooves or too fast injection speed are the main causes.
Solution
①Open/deepen vent grooves at the burnt position (ABS vent depth about 0.02~0.04mm); ②clean the vents blocked by oil; ③reduce the end injection speed; ④reduce the amount of mold release agent.
Key Takeaway
Repeated burning at a fixed position=venting problem; clean the vent grooves first.
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