Key Mold Design Points for High‑Temperature PEEK Injection Molding

PEEK belongs to high‑performance high‑temperature engineering plastic with outstanding heat resistance, mechanical strength, corrosion resistance and wear‑resisting properties. It is widely adopted for medical devices, aerospace components and precision mechanical parts. Compared with common plastics such as ABS and PP, PEEK features high melting temperature, poor melt flowability and special molding shrinkage. It imposes strict requirements on mold structure, material selection, temperature control and venting. Standard general‑purpose injection molds easily generate incomplete filling, burning, stress cracking, dimensional deviation and surface streaking. Targeted optimization of mold details based on PEEK material characteristics is essential to secure molded‑part quality and stable production.

1. Mold Steel Selection and Heat‑Treatment Specifications

PEEK molding temperature reaches 380‑420 degrees Celsius. Molds operate under sustained high‑temperature conditions. Ordinary mold steels suffer deformation, wear and cavity collapse under such working conditions. High‑hardness corrosion‑resistant mirror‑grade mold steels including S136 and STAVAX are preferred for PEEK molds to resist high‑temperature melt corrosion and long‑term friction wear. Steel blanks shall receive complete quenching and tempering heat‑treatment, achieving hardness ranging from HRC50 to HRC55. Proper hardness prevents cavity deformation and edge collapse while supporting high‑level surface polishing for cosmetic‑critical PEEK parts. Steels such as 45# steel and P20 are strictly prohibited for PEEK mold manufacturing. These materials cannot withstand sustained high temperature and quickly develop cavity oxidation, surface pitting and dimensional drift in mass production.

2. Precise Layout of Temperature‑Control Circuits

Temperature control acts as the core factor for PEEK molding. Uneven mold temperature creates excessive internal stress, warpage and cracking on molded parts. Simple straight cooling channels for conventional molds cannot satisfy PEEK constant‑temperature requirements. PEEK molds require independent, dense and evenly distributed heating‑cooling circulating channels. Mold surface temperature shall be maintained stably between 160‑190 degrees Celsius. Cooling channels follow contour of mold cavities, keeping consistent depth and spacing. Channels must stay close to molding surfaces. Mold inserts and cores shall be equipped with dedicated cooling lines. Mold temperature deviation shall be controlled within ±5 degrees Celsius. Independent temperature‑controller interfaces are reserved. Sharing temperature‑control equipment with ordinary molds shall be avoided to prevent slow heating and violent temperature fluctuation. Well‑designed temperature circuits reduce internal stress and improve dimensional stability of PEEK workpieces.

3. Optimization of Gating and Runner Systems

PEEK melt features high viscosity and poor flowability. Thin runners and small gates cause filling difficulty, heavy pressure loss and local material burning. Runner systems adopt large‑cross‑section and short‑flow‑path principles to lower flow resistance. Straight runners or trapezoidal runners are recommended. Side gates, fan gates and direct sprue gates are preferred with enlarged gate cross‑section. Point gates and small submarine gates should be avoided to prevent excessive shear and material carbonization. All runner corners apply smooth fillet transitions to eliminate dead corners where melt may stagnate and degrade. Multi‑cavity molds implement balanced runner layout to guarantee consistent injection pressure and flow speed for every cavity, minimizing weight and dimensional discrepancy. Runner surfaces require fine polishing to reduce flow friction and filling defects.

4. Enhanced Venting System Design

PEEK releases trace decomposed gas under high‑temperature melting. Violent air compression occurs during high‑pressure injection. Insufficient venting causes burning, bubbles, surface pitting and incomplete filling. Venting standards for PEEK molds exceed requirements for ordinary plastic molds. Wide and deep vent slots are arranged at melt end positions, weld‑line zones, thick‑wall dead corners and cavity corners. Vent slot depth strictly complies with PEEK material parameters to balance venting performance and flash prevention. Parting lines and insert fitting gaps must support gas evacuation without over‑sealing. For complex deep‑cavity thin‑wall PEEK parts, auxiliary vent inserts are installed to fully discharge trapped air and decomposed gas, eliminating burning and flow‑mark defects.

5. Ejection and Demolding Structural Design

Molded PEEK parts deliver high rigidity and stable shrinkage rate, yet exhibit strong mold‑holding force after cooling and higher brittleness compared with general plastics. Improper ejection structures lead to ejection whitening, cracking and part deformation. Multi‑point balanced ejection structures increase ejector pin cross‑section and ejection points to disperse ejection stress. Combination of ejector pins and push plates is recommended for thin‑wall high‑precision PEEK components to avoid stress concentration from single‑point ejection. Fit clearance of all ejection components is precisely calibrated to prevent jamming caused by thermal expansion under high‑temperature working conditions. Demolding draft angle shall be increased by 1‑2 degrees compared with ordinary plastic molds to reduce friction during demolding and eliminate surface scratching and cracking risks.

Conclusion

PEEK high‑temperature plastic mold design focuses on high‑temperature resistance, precise temperature stabilization, low‑resistance gating, sufficient venting and balanced ejection. Distinct from conventional injection molds, PEEK molds enforce strict standards for steel performance, temperature accuracy, runner structure and venting. Adopting corrosion‑resistant high‑hardness mirror steel, evenly distributed temperature circuits, balanced large‑flow gating systems, enhanced venting structures and stable ejection assemblies resolves common PEEK molding defects. These measures guarantee dimensional accuracy, structural stability and cosmetic quality, supporting mass production of high‑end precision PEEK components.