Extrusion & Post
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HDPE pipe dimensional instability
Problem Phenomenon
In the same shift, the measured pipe outer diameter and wall thickness drift, synchronized with extrusion output fluctuation.
Cause Analysis
Barrel temperature fluctuation changes melt viscosity and discharge; unstable haul-off speed directly changes the pipe draw ratio, and the two superimpose to cause dimensional drift.; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based on experience alone
Solution
①Stabilize the temperature of each barrel section; ②check the heating bands and thermocouples; ③calibrate the haul-off speed closed-loop control; ④monitor melt pressure stability.; after adjustment, take consecutive samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Dimensional stability depends on the dual stability of temperature and haul-off; melt pressure monitoring is a direct window into discharge stability.; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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