Processing Machinery
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PMMA Thick-Wall Part Vacuum Voids
Problem Phenomenon
Vacuum voids appear in the center of thick-wall transparent parts, holes are visible on sectioning, and optical parts are directly scrapped.
Cause Analysis
The surface layer of thick areas solidifies first, and internal shrinkage forms vacuum voids; although PMMA shrinkage is not large, they still form after the feeding channel of ultra-thick sections freezes.; During on-site troubleshooting, verify item by item according to this mechanism to avoid blindly adjusting the machine based on experience alone.
Solution
①Core-out and thinning design for thick areas; ②extend holding pressure time; ③raise mold temperature to delay freezing; ④evaluate layered injection for thick-wall optical parts.; After adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability.
Key Takeaway
Vacuum voids are a fatal defect of thick-wall transparent parts; structural thinning is fundamental, and thick optical parts also need dedicated process evaluation.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence.
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