Injection Molding
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PC Injection Melt Temperature Actually Measured Too High
Problem Phenomenon
The barrel setting is normal but the actually measured melt temperature exceeds the upper limit, and products turn yellow.
Cause Analysis
Excessive screw speed/back pressure generates a large amount of shear heat, making the actual melt temperature far higher than the set value; PC is sensitive to overheating, and shear heat is an invisible overtemperature source; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience.
Solution
①Reduce screw speed and back pressure; ②Use a thermometer to actually measure the melt temperature to calibrate the process; ③Check whether the screw compression ratio is suitable for PC; ④Optimize the combination of screw speed and back pressure, taking both plasticization and shear heat into account; ⑤Monitor the melt temperature trend.
Key Takeaway
PC 'set temperature ≠ melt temperature': shear heat must be actually measured; PC is sensitive to overheating, the actual melt temperature must be included in monitoring, not just looking at the displayed setting; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence.
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