Extrusion & Post
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Sharkskin on LCP Extruded Profile Surface
Problem Phenomenon
【Problem Phenomenon】Periodic rough sharkskin patterns appear on the surface of LCP extruded rods or sheets
Cause Analysis
Alternating slip-stick of the melt at the die wall causes melt fracture, and sharkskin appears when the shear rate reaches a critical value; high-temperature low-viscosity LCP also has critical shear problems in high-output extrusion
Solution
Reduce the extrusion line speed or raise the die temperature to reduce shear stress; polish the die flow channel to reduce resistance; if necessary, add processing aids to promote wall slip; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Sharkskin is a signal of shear exceeding the critical value; lowering temperature and raising speed is not as good as matching speed increase with temperature decrease; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a troubleshooting reference for subsequent similar problems
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