Injection Molding
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PC Frequent Black Specks at Injection Startup
Problem Phenomenon
In the first dozens of shots after each startup there are many black specks, which then gradually decrease, showing startup correlation.
Cause Analysis
During shutdown, the material in the barrel/hot runner carbonizes and is carried out by new material at startup; not lowering the temperature or not purging at shutdown is the direct cause; PC carbonizes obviously at high temperature; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience.
Solution
①Shutdown exceeding the specified time must lower the temperature or purge; ②Flush with purging material before startup; ③Record startup scrap shots and optimize the SOP; ④Avoid long-time heat preservation; ⑤Purge regularly.
Key Takeaway
PC startup black specks = 'shutdown management problem': lowering temperature and purging at shutdown is an iron rule; the number of startup scrap shots is a direct measure of whether the shutdown SOP is in place; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence.
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