Injection Molding
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ABS jetting marks (snake marks)
Fenómeno del problema
When the gate faces an open cavity, snake-shaped, earthworm-like twisted lines appear on the product surface, extending from the gate into the cavity.
Análisis de la causa
The melt jets into the cavity without contacting the cavity wall after passing through the small gate at high speed; the melt strand folds and cools to form jetting marks; too high initial injection speed and too small gate are the main causes, and the gate facing the empty cavity is the structural condition.
Solución
①Change the gate direction so that the melt first hits the cavity wall or core; ②reduce the injection speed in the initial section and then increase it step by step; ③enlarge the gate; ④use a lap gate; ⑤appropriately increase the mold temperature.
Conclusión clave
For ABS jetting marks, 'let the material hit the wall first when entering': the gate design cooperates with the speed curve so that the front adheres to the wall and spreads as soon as it enters the cavity, and the snake marks disappear immediately, which preserves capacity better than simply reducing speed.
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