Injection Molding
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Large Injection Pressure Fluctuation in Block Copolymer Polypropylene '2079851475616104452
Problem Phenomenon
The pressure gauge reading fluctuates greatly during the injection process, and the pressure difference within the same cycle or between different cycles exceeds ±5%.
Pressure fluctuation causes unstable product weight, dimensions, and quality, and in severe cases short shot or flash appears alternately.
Cause Analysis
（1）The hydraulic system pressure is unstable, the hydraulic pump is worn, or the hydraulic oil is contaminated
（2）The screw check ring is worn, and the injection amount is inconsistent each time
（3）The barrel temperature fluctuates greatly, and the melt viscosity change causes pressure fluctuation
（4）The discharge is uneven, and the plasticizing amount is inconsistent each time
（5）The screw rotation speed is unstable, and the plasticizing quality fluctuates
Solution
（1）Check the hydraulic system, repair or replace the worn hydraulic pump, and replace the hydraulic oil
（2）Check the check ring, and replace it if the wear exceeds 0.1mm
（3）Stabilize the barrel temperature, with the fluctuation of each section controlled within ±3°C (200-270°C range)
（4）Check the discharge system to ensure smooth hopper discharge and stable material level
（5）Stabilize the screw rotation speed and back pressure to ensure plasticizing consistency
Key Takeaway
Injection pressure fluctuation is caused by hydraulic system instability or plasticizing inconsistency, and the hydraulic, screw, and temperature control systems need to be systematically investigated.
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