Injection Molding
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Unstable Screw Retraction in High-Density Polyethylene '2079851475616104452
Fenómeno do problema
The screw jumps during plasticization retraction, the retraction speed is uneven, or the retraction is not in place, and the pre-plasticization position fluctuates greatly.
Unstable screw retraction leads to inconsistent injection amount each time, directly affecting product weight and dimensional stability.
Análise das causas
(1) The back pressure is set too high or unstable, and the plasticization resistance is large
(2) The barrel temperature is uneven, and the melting section temperature is too low, causing plasticization difficulties
(3) The screw is severely worn, and the plasticization efficiency decreases
(4) The raw material particle size is uneven or contains too much powder, and the feeding is uneven
(5) The screw speed and back pressure are improperly matched
Solução
(1) Appropriately reduce the back pressure to 3-8MPa to ensure stable back pressure
(2) Check the temperature of each section of the barrel to ensure the melting section temperature is at a reasonable value within the range of 180-260°C
(3) Check the wear of the screw; replace the screw if the thread clearance exceeds 0.2mm
(4) Screen the raw material and control the powder ratio to not exceed 5%
(5) Adjust the matching relationship between the screw speed and the back pressure, with a speed of 40-100rpm
Conclusão principal
Unstable screw retraction is caused by large plasticization resistance or equipment wear, and the back pressure, temperature, and screw condition need to be optimized.
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