Processing Machinery
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PMMA Back Pressure Control
Problem Phenomenon
Products turn yellow after the PMMA melt back pressure is too high
Cause Analysis
High back pressure generates heat by shear, raising the actual melt temperature and causing PMMA thermal degradation; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience; this mechanism has been repeatedly verified by industry literature and should be confirmed first during troubleshooting
Solution
Control back pressure at 0.3-0.7MPa; when yellowing occurs, first check back pressure and screw speed; after adjustment, take samples continuously to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PMMA back pressure should be low; shear heat is a hidden temperature rise; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a reference for troubleshooting similar problems in the future
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