Molds & Tooling
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PMMA Optical Part Slow Cooling
Problem Phenomenon
PMMA thick lenses show internal stress patterns after ejection from the mold
Cause Analysis
Uneven cooling inside and outside of thick-walled optical parts produces stress birefringence; 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
Take the upper limit of mold temperature and extend cooling; slow cooling in an insulated box after ejection; anneal when necessary; after adjustment, take samples continuously to verify the effect, and resume mass production only after confirming stability; change only one variable at a time and record parameter changes to facilitate locating effective measures
Key Takeaway
Slow cooling of thick optical parts is a necessary process to relieve stress; 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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