Material Drying
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PA66 yellowing control
Problem Phenomenon
PA66 natural-color products are yellowish, and the difference from the color plate is out of tolerance
Cause Analysis
Melt temperature too high or residence too long causes thermal oxidative yellowing; over-temperature drying also causes pre-yellowing, segmented troubleshooting is needed; during on-site troubleshooting, verify item by item according to this mechanism, avoiding blindly adjusting the machine based only on experience
Solution
Measured melt temperature not exceeding 295℃; drying temperature not exceeding 90℃; residence time controlled; use fresh material for light-color products; after adjustment, take continuous samples to verify the effect, confirm stability before resuming mass production
Key Takeaway
Yellowing is investigated and temperature reduced segment by segment in the drying section and molding section; after confirming effectiveness, fix the parameters and practices into the work instructions to prevent recurrence; include this case in the defect archive as a troubleshooting reference for subsequent similar problems
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