Processing Machinery
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LDPE Screw Speed
Problem Phenomenon
After raising screw speed, sharkskin appears on the LDPE film.
Cause Analysis
Higher speed raises shear rate beyond the critical value, causing melt fracture; During on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience; This mechanism has been repeatedly verified by industry literature and should be confirmed first during troubleshooting.
Solution
Control speed to keep shear below the critical value; add PPA aid to widen the window; After adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability; Change only one variable at a time and record parameter changes to facilitate locating effective measures.
Key Takeaway
Screw speed is managed by the melt fracture critical value; After confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence; Incorporate this case into the defect archive as a troubleshooting reference for similar future problems.
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