Injection Molding
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PP '2079851475616104452 Cold Slug Mark
Fenómeno do problema
Misty, pock-like small spots appear near the gate, inconsistent with the matrix in gloss and color, reappearing in the next shot after removal.
Análise das causas
Cold material at the nozzle or runner front is carried into the cavity in the next shot and fails to fuse with new melt, leaving traces; too small cold slug wells, low nozzle temperature, and excessive nozzle-mold contact time all cause repeated cold slug formation.
Solução
①Enlarge or add cold slug wells at key positions to 'catch' the cold front material; ②appropriately raise nozzle temperature; ③check whether nozzle heater bands and thermocouples are normal; ④shorten nozzle-mold contact time; ⑤optimize gate position to reduce cold material entering the cavity.
Conclusão principal
The antidote for PP cold slug marks is 'cold slug well + nozzle temperature': first guide cold material into the cold slug well, then ensure nozzle temperature is not low; recurring fixed-position small spots are mostly due to inadequate cold slug well design.
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