Injection Molding
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PMMA Injection Speed Shear Marks
Problem Phenomenon
Shear marks and haze spots appear on product surfaces during high-speed filling, disappearing after speed reduction.
Cause Analysis
When PMMA high-viscosity melt passes through a narrow cross-section at high speed, shear overheating occurs, and surface molecular chains are damaged forming misty shear marks.; During on-site troubleshooting, verify item by item according to this mechanism to avoid blindly adjusting the machine based on experience alone.
Solution
①Adopt a medium-speed filling profile; ②enlarge gate and runner; ③appropriately raise melt temperature to reduce viscosity; ④avoid sudden speed changes.; After adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability.
Key Takeaway
Shear marks indicate that speed exceeds the material's tolerance; PMMA should be filled smoothly at medium speed, and trading temperature for speed is safer.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence.
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