Generic "PEEK molding parameters" circulating online are usually extrapolated from commodity plastics, and the drying and mold-temperature figures are the ones most often wrong. What follows are engineering values from specialty-plastic equipment and tooling; final settings are optimized during trials for your specific part.
PEEK must run through a desiccant dryer at 150 °C for 3–6 hours with residual moisture below 0.02 %. Under-dried material produces bubbles, silver streaks and a measurable loss of mechanical properties. This step is not negotiable and it is not shortened under delivery pressure.
PEEK's 343 °C melting point leaves a narrow processing band. Barrel zones are set from 360 °C up to 400 °C, verified against the grade's datasheet rather than by habit from commodity plastics.
Crystallinity — and therefore strength, dimensional stability and wear resistance — is decided by how the part cools. We run 160–220 °C oil temperature control with mold-face uniformity within ±2 °C, on independent circuits for core and cavity. Screw and barrel use corrosion-resistant alloy with a compression ratio of 2.5–3:1, an L/D of 20–24:1 and no dead pockets.
Precision parts are annealed at 200 °C for 2–4 hours and then cooled slowly in the furnace to release internal stress and stabilize dimensions and crystallinity. This step is the answer to the classic complaint that a precision PEEK part "moved after two days" — and it is the step most often skipped.
| Defect | Main cause | Countermeasure |
|---|---|---|
| Warpage | Uneven mold temperature, uneven cooling | Conformal cooling, independent circuits, annealing |
| Bubbles / silver streaks | Insufficient drying, melt too hot | Re-dry, lower melt temperature, check runner |
| Sink marks / voids | Low holding pressure, gate freezing early | Enlarge gate, longer hold, higher holding pressure |
| Burns / scorch marks | Poor venting, excessive shear | Add vents 0.015–0.02 mm deep, slower injection |
| Stress cracking | Cooling too fast, insufficient annealing | Raise mold temperature, standardize annealing |
| Short shot | Insufficient pressure or mold temperature | Raise injection pressure and mold temperature, enlarge runner |
| Weak weld lines | Low melt temperature, poor venting | Raise melt and mold temperature, relocate gate |
Steel selection, gating, temperature control, venting, ejection and tolerance control in detail.
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The equipment and handling discipline behind a repeatable PEEK process.
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