Injection Molding
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PMMA Surface Flow Marks and Jetting Marks
Problem Phenomenon
Ripples or snake-like flow marks appear near the gate; the marks are easily visible on transparent parts, and improve after adjusting speed and gate.
Cause Analysis
A too-small or improperly positioned gate causes the melt to jet-fill; low melt or mold temperature, or injection speed too fast or too slow, all form visible flow marks.; During on-site troubleshooting, verify item by item according to this mechanism to avoid blindly adjusting the machine based on experience alone.
Solution
①Enlarge the gate and optimize its position; ②adjust the injection speed profile; ③raise melt and mold temperature; ④improve venting.; After adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability.
Key Takeaway
Flow marks affect the optical appearance that PMMA values most; gate design and speed profile are the main control means, and fan gates with slow filling are recommended for optical parts.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence.
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