Injection Molding
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PC Jetting Marks (Snake Pattern)
Fenómeno del problema
When the gate faces an open cavity, snake-shaped curved marks appear on the product surface, appearing as twisted stripes on transparent parts, appearance unqualified.
Análisis de la causa
After the high-viscosity melt is ejected from the gate at high speed without hitting the wall, the melt strand folds and accumulates in the air; excessive initial injection speed, a small gate, and the gate facing an open cavity are the three main conditions, and PC's high viscosity makes the melt strand easier to keep its shape and form twisted marks.
Solución
①Change the gate angle so that the melt stream first hits the cavity wall or core; ②Reduce the initial injection speed and then speed up; ③Enlarge the gate; ④Appropriately increase the mold temperature; ⑤Switch to an overlap gate when necessary.
Conclusión clave
PC jetting marks 'let the melt stream stick to the wall first and then spread out': gate design coordinated with the speed curve lets the front stick to the wall as soon as it enters the cavity; jetting marks on transparent parts have nowhere to hide, and gate direction design must avoid it from the source.
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