Injection Molding
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EVOH '2079851475616104452 Cold Slug Marks
Problem Phenomenon
EVOH injection molded products show cold slug marks near the gate
Cause Analysis
Nozzle temperature too low causing residual material from the previous shot to cool and solidify in the nozzle; cold slug well design insufficient to hold cold material; injection pressure insufficient
Solution
1) Increase nozzle temperature to 190-230°C; 2) Mold design with sufficiently large cold slug well; 3) Ensure fresh melt at the nozzle front before each shot; 4) Increase injection pressure to push cold material through the gate
Key Takeaway
Cold slug marks are caused by solidified residual material in the nozzle; increasing nozzle temperature and cold slug well design are key
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