multi-cavity Injection Molding PEI Part

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'll almost get the silver streaks or bubbles.

Melt temperature should be set between 350°C and 400°C, with mold temperature maintained at 135°C–165°C to ensure proper flow and minimize internal stresses. For this 1-out-4 configuration, a balanced runner layout is essential, with all cavities arranged at equal distance from the sprue to ensure uniform filling. A hot runner system with a valve gate is recommended for the 1-out-4 layout, allowing independent temperature control at each nozzle and minimizing material waste. To match the symmetrical part layout, a circular cooling circuit is recommended, with baffles positioned around the core pins and inserts to ensure uniform cooling across all four cavities. 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 seconds depending on wall thickness, and screw speed is set at 40–70 rpm.

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