Processing Machinery
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PMMA Hot Bending Bubbles and Cracking
Problem Phenomenon
Bubbles appear on the sheet surface or cracking occurs at bending corners during hot bending; improvement after lowering heating temperature and stepped cooling.
Cause Analysis
Excessively high heating temperature over-softens the sheet surface layer and produces bubbles; too-fast cooling causes inconsistent shrinkage inside and outside, and cracking occurs at bending corner stress concentration areas.; During on-site troubleshooting, verify item by item according to this mechanism to avoid blindly adjusting the machine based on experience alone.
Solution
①Control heating temperature at 150~160℃; ②cut micro grooves before hot bending thick sheets to release stress; ③stepped cooling after hot bending; ④avoid rapid cold-water quenching for setting.
Key Takeaway
Hot bending quality relies on temperature and cooling rhythm control; stepped cooling (60℃→40℃→room temperature) is an effective method to eliminate hot bending stress.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence.
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