Injection Molding
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PC Short Shot Caused by High Viscosity
Problem Phenomenon
Thin-wall or long-flow PC products cannot be filled, the short-shot edges are rounded, it recurs at the same position, and improvement after raising pressure is limited.
Cause Analysis
PC melt viscosity is much higher than general-purpose plastics, and flow resistance is large; low melt temperature, insufficient injection pressure/speed, and too small a gate all amplify filling difficulty; the thin-wall long-flow structure itself is a challenge for high-viscosity materials.
Solution
①Raise the melt temperature to near the recommended upper limit (not exceeding the degradation temperature) to reduce viscosity; ②Increase injection pressure and speed; ③Enlarge the gate and runner and shorten the flow length; ④Increase the mold temperature to delay solidification; ⑤Select high-flow grades when necessary.
Key Takeaway
For PC short shot, first 'raise temperature and speed up', then 'large gate', and finally 'change grade': high viscosity is PC's nature; when the structure allows, shortening the flow length and enlarging the gate is more effective than forcibly raising pressure, and also better protects the mold.
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