Molds & Tooling
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PA6 Product Melt Fracture Marks
Problem Phenomenon
Hazy marks on the surface during high-speed filling, mostly occurring near the gate.
Cause Analysis
Excessively high shear rate makes the surface layer unstable; small gate; PA6 low viscosity and high-speed filling make the surface layer easily unstable; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience.
Solution
①Reduce the injection speed when passing through the gate to reduce shear heat;②appropriately enlarge the gate to reduce shear rate and pressure loss;③appropriately increase mold temperature to improve the melt's replication and fit to the cavity surface;④optimize the injection speed curve to keep the melt front advancing smoothly;⑤polish the gate.
Key Takeaway
PA6 shear marks = 'gate buffering': bring down the speed through the gate and enlarge the gate; low-viscosity material high-speed filling must guard against surface layer instability; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence.
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