Molding Process
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PMMA Burnt Degradation
Problem Phenomenon
Product ends are charred black and discolored, transparent parts show yellow streaks, and odor is abnormal
Cause Analysis
PMMA thermally degrades at high temperature or long residence; shear heat superimposed on set temperature makes the actual melt temperature exceed the standard; transparent parts are extremely sensitive to degradation, and slight degradation manifests as yellow streaks
Solution
①Control melt temperature not to exceed the upper limit; ②shorten residence time and stabilize production rhythm; ③reduce screw speed and back pressure when shear heat is high; after adjustment, take samples continuously to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PMMA transparent parts have extremely low degradation tolerance; three variables of temperature, residence, and shear are managed in linkage; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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