Injection Molding
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PEEK Injection Pressure and Back Pressure Window
Problem Phenomenon
[Problem Phenomenon] Insufficient filling and shear discoloration of PEEK alternate, and pressure parameters can hardly satisfy both
Cause Analysis
PEEK melt has high viscosity and needs 100-150MPa injection pressure to ensure filling; but back pressure exceeding 10MPa causes shear degradation and discoloration, and the screw speed is limited to 40-80rpm; both the pressure and shear windows of high-viscosity material are narrow
Solution
Take the injection pressure at 100-150MPa according to the flow length; back pressure of 5-10MPa is enough to expel volatiles — do not exceed the limit; plasticize with the screw at 40-80rpm low shear; use injection speed rather than back pressure to compensate for thin-wall parts
Key Takeaway
PEEK requires high injection pressure and low back pressure — for shear discoloration, check back pressure and screw speed first; 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 similar problems in the future
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