How to Achieve Precision Molding of PEEK via Injection Molds

PEEK (polyetheretherketone), a "super engineering plastic" with continuous heat resistance up to 260°C, metal-grade mechanical strength, and excellent corrosion resistance, is a core material in high-end fields like aerospace and medical implants. However, its high viscosity and crystallinity impose strict requirements on injection molds—mold design accuracy directly determines whether products can meet ±0.005mm dimensional precision and performance indicators. Below is an analysis of precision molding pathways based on core mold design dimensions and latest practical data.

1. Gating System: Core of Precise Melt Filling

As the "interface" for melt injection into the cavity, gating design affects filling uniformity and defect rates. Needle valve hot runner gates are preferred for precision products, paired with a 343-420°C precise temperature control system. For 0.8mm thin-walled phone lens holders, this extends gate solidification time to 1.2x the filling cycle, reducing short shot rates from 3% to below 0.1%.

(1) Position Design Principles

Follow the rule of "target thick walls, avoid ends, stay away from key areas"—verified across over 120 mold sets, this cuts defect rates by over 40%.

Example: For a φ20mm bearing sleeve mold, the gate is set at a 4mm-thick side protrusion, keeping circumferential melt filling speed difference ≤0.5m/s and roundness error within 0.005mm (surpassing the industry 0.01mm standard).

Multi-cavity solution: A new energy motor end cover uses 3 gates opened at 0.2s intervals to eliminate weld lines, retaining 95% tensile strength.

(2) Dimensional Standards

Width = 1.5-2x product wall thickness; thickness = 0.5-0.8x product wall thickness; length = 3-5mm.

Example: For a 3mm-thick aerospace connector mold, gate thickness adjusted from 1.5mm to 1.8mm eliminates sink marks, with residual traces ≤0.3mm.

2. Runner System: Key to Reducing Resistance & Balancing Filling

For PEEK’s high viscosity, circular runners are optimal—reducing flow resistance by 30% vs. trapezoidal runners.

(1) Basic Parameter Design

Runner diameter is graded by product weight: 6mm for <50g, 12mm for >100g, with arc corners to avoid melt degradation. Multi-cavity molds require strict "triple balance":

Path difference ≤5%

Diameter error ≤0.2mm

Pressure loss difference ≤3MPa

Example: An 8-cavity small gear mold uses a spoke-type layout, with melt arrival time difference across cavities only 0.1s and dimensional consistency up to 99.5%.

(2) Hot Runner Application

Hot runners are essential, with zone temperature control ensuring ±1°C error.

Benefit data: For sensor housings, hot runners reduce scrap rate from 20% to 0.8%, saving RMB 220,000 in annual material costs and cutting cycle time by 8s.

Special adaptation: PEEK-HT grades require custom 420°C high-temperature heating elements to prevent equipment damage.

3. Cooling System: Core for Controlling Shrinkage & Deformation

Based on PEEK’s high crystallinity, the cooling system follows "close to cavity, uniform distribution".

(1) Conventional Design Parameters

Cooling channels are 15-25mm from the cavity wall, 8-12mm in diameter, with ≥90% conformity to product shape.

Example: Spiral channels for circular bearing sleeves improve cooling uniformity by 50% vs. straight channels.

(2) Medium & Technology Upgrade

Differentiated Medium Selection:

Standard grades: 25-35°C cooling water at 3-5m/s, paired with ≤0.5°C/s response temperature controllers;

Special grades: 280°C high-temperature heat transfer oil for PEEK-HT—reducing gear mold deformation from 0.15mm to 0.03mm.

3D-Printed Conformal Channels:

Example: For a deep-cavity valve seat mold, cooling area increases by 60%, cooling time shortens from 60s to 35s (71% efficiency gain), and warpage ≤0.02mm.

4. Material & Venting: Guarantee for Mold Durability & Molding Quality

(1) Mold Material Selection

High-temperature/high-pressure resistant alloy steel with thermal conductivity ≥40W/(m·K) is preferred, paired with Ra≤0.8μm channel polishing to enhance heat dissipation. For mineral-filled PEEK, fine mold surface polishing reduces fiber floating and gloss defects.

(2) Venting System Optimization

Vents: 0.01-0.02mm deep, 5-10mm wide—effectively resolving gas porosity.

(3) Synergy with Material Preprocessing

PEEK raw materials require drying at 120-150°C for 4-6 hours. Fiber-reinforced grades need synchronized mold structure and process parameter optimization to avoid stress concentration and surface defects.

5. Conclusion

PEEK precision molding relies on multi-system synergy: gates control filling accuracy, runners ensure melt quality, cooling determines dimensional stability, and material matching extends mold life. With quantitative design standards, advanced hot runner technology, conformal cooling, and strict material preprocessing, ±0.005mm precision and excellent mechanical properties are achievable—supporting high-end manufacturing. Future efforts should focus on intelligent matching of molds and process parameters to enhance molding stability for complex products.