High Precision PEI Parts

Thorough Drying
PEI is highly hygroscopic, so before molding we need to dry it at 150°C for at least 4 hours to get moisture content below 0.02%. If we skip this or cut corners, we are almost certain to get silver streaks or bubbles.

Injection Process Control
Melt temperature should be set between 350°C and 400°C, with mold temperature maintained at 135°C–165°C to ensure proper flow into thin ribs and minimize internal stresses. Injection pressure generally ranges from 80–120 MPa, while holding pressure is about 50–70% of the injection pressure to reduce shrinkage and warpage. Injection speed should be medium to high to avoid premature freezing in the thin-walled sections, and back pressure is kept low at 0.3–0.7 MPa. Cooling time usually ranges from 20–40 seconds depending on wall thickness, and screw speed is set at 40–70 rpm. Due to PEI's high processing temperature and moisture sensitivity, we use a hot runner system with precise temperature control, and the mold is designed with adequate venting and heating capacity to maintain uniform cavity temperature.

Stress Relief
Post-mold annealing at 180°C–200°C for 2–4 hours is typically applied to relieve internal stress and optimize mechanical properties.