Injection Molding
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COC Improper Mold Temperature Setting Poor Surface
Problem Phenomenon
COC optical parts have poor surface replicability, obvious flow marks, uneven gloss, increasing injection speed gives limited improvement, surface quality never reaches optical grade.
Cause Analysis
COC is an amorphous material, mold wall temperature has great influence on surface replication; when mold temperature is too low the melt surface layer is quenched and cannot replicate the cavity mirror; high surface requirement parts need high mold temperature close to Tg.
Solution
①Raise mold temperature to the range about 10℃ below Tg and match with high injection speed; ②the higher the surface requirement the higher the mold temperature; ③verify mold heating capacity reaches 95~130℃ range; ④cavity mirror polishing matched.
Key Takeaway
The core lever of COC surface quality is mold temperature; high mold temperature process close to Tg is standard for optical parts; mold temperature controller selection must cover the high-temperature section with precise control.
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