Molds & Tooling
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PC Black Specks (Carbonized Spots)
Problem Phenomenon
Small black specks appear in transparent or light-colored PC parts, randomly distributed, zero tolerance on transparent parts.
Cause Analysis
Material accumulated in hot runner dead corners and barrel dead corners carbonizes and falls off at high temperature; incomplete purging during material change and raw material contamination also introduce black specks; PC's high processing temperature makes dead-corner accumulated material easier to carbonize.
Solution
①Clean hot runner and nozzle dead corners; ②Avoid long shutdowns with heat preservation; ③Use purging material to thoroughly replace during material change; ④Check raw material cleanliness; ⑤Establish a regular purging and maintenance system.
Key Takeaway
Transparent PC's tolerance for black specks is zero: dead-corner treatment must be normalized and institutionalized; intermittent black specks are a typical feature of dead-corner carbon deposits, and purging is far more effective than adjusting the process.
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