Processing Machinery
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LDPE Screw Speed
Fenómeno do problema
After raising screw speed, sharkskin appears on the LDPE film.
Análise das causas
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.
Solução
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.
Conclusão principal
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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