Injection Molding
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PA66 '2079851475616104452 jetting marks
Problem Phenomenon
Snake-like marks, obvious when the gate faces an empty cavity.
Cause Analysis
High speed through a too-small gate; high initial speed; melt does not touch the wall and folds; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based solely on experience; during troubleshooting, confirm item by item around key factors such as jetting marks and gate to avoid misjudgment.
Solution
①Change gate direction so the melt hits the cavity wall first after entering and then spreads; ②decelerate at the injection start section, pass the gate at low speed and then speed up; ③appropriately enlarge the gate to reduce shear rate and pressure loss; ④appropriately raise mold temperature to improve melt replication and fit to the cavity surface; ⑤switch to an overlap gate to avoid melt jetting directly into the cavity.
Key Takeaway
PA66 jetting mark='hit the wall at entry': gate direction coordinates with the speed curve; letting the front spread against the wall can eliminate it; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence.
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