What to pay attention to PEEK injection mold?

PEEK (polyether ether ketone) is a high-performance engineering plastic with excellent mechanical properties, high-temperature resistance, chemical resistance and biocompatibility, and is widely used in aerospace, medical devices, electronics, electrical and other high-end fields. However, due to the special physical and high-temperature resistant chemical properties of PEEK material, its injection molding processing and mold design are quite different from ordinary plastics. In the design and manufacturing process of PEEK molds, special attention needs to be paid to the following points.

I. Selection of mold materials

1. High-temperature alloy steel

The melting point of PEEK is as high as 343°C, and the injection molding process temperature is usually between 360°C and 400°C. Molds need to be able to withstand high temperatures, so it is appropriate to choose high-temperature alloy steel, such as H13, S136, NAK80 and so on. These materials have excellent high temperature strength, hardness and wear resistance.

2. Corrosion resistance

PEEK may release acidic gases at high temperatures, causing corrosion to the mold. Select corrosion-resistant mold materials, or hardening and anti-corrosion treatment of the mold surface, such as chrome plating, nitriding and other processes.

Second, the main points of mold design

1. Reasonable pouring system

• Hot Runner Applications
  Due to the high processing temperature of PEEK, hot runner systems need to be made of high temperature resistant materials with good temperature control to prevent material degradation in the runner.
• Gate Design
  The gate size should be increased appropriately to minimize shear stress and avoid material degradation. It is recommended to use straight or fan-shaped gates to ensure smooth filling of the melt.

2. Mold temperature control

• High Temperature Molding Machine
  The mold temperature needs to reach 160°C~220°C, ordinary mold thermostat can not meet the demand. Need to use high-temperature oil thermostat (not environmentally friendly), to ensure that the mold temperature is uniform and stable.
• Cooling System Layout
  Design efficient cooling circuit to avoid local overheating or overcooling of the mold, which will affect the dimensional stability and surface quality of the products.

3. Exhaust design

PEEK melt has high viscosity and relatively poor flowability, which makes it easy to produce bubbles and fusion marks. The mold needs to be designed with effective exhaust slots, especially at the end of the flow and thick-walled parts.

III. Precautions for Processing Techniques

1. Precise temperature control

• Cylinder temperature
  The temperature of each section of the barrel needs to be set accurately, generally 360°C to 400°C. Too high or too low will result in material degradation or underfilling.
• Mould temperature
  The mold temperature has a significant impact on the crystallinity and mechanical properties of the products, which should be strictly controlled within the range of 160°C~220°C.

2. Injection speed and pressure

• injection speed
  Low to medium injection speeds were used to avoid material degradation due to excessive shear rates.
• injection pressure
  The injection pressure should be high enough to overcome the resistance caused by the high viscosity of the melt to ensure complete filling of the product.

3. Dried material handling

PEEK is extremely sensitive to moisture and must be fully dried before processing. Usually, the material is dried at 150°C for 3~4 hours, and the residual moisture is controlled below 0.02%.

IV. Mold manufacturing and surface treatment

1. High-precision machining

PEEK products are mostly used in high-end fields, requiring high dimensional accuracy, often in the ± 0.05mm ~ 0.01mm. mold processing needs to use high-precision CNC equipment to ensure that the mold parts size tolerance of ± 0.02mm ~ 0.001mm or less, in order to make high-precision injection molded products.

2. Surface polishing and finishing

• high gloss
  The surface of the mold cavity should be mirror polished to reduce the product surface defects and improve the demolding effect.
• surface coating
  In order to improve the wear resistance and corrosion resistance of the mold, the surface of the cavity can be chromium-plated, titanium-plated and other treatments.

V. Demolding problems and solutions

1. Demolding slope

Because PEEK products are easy to stick to the mold, need to design enough demolding slope, usually 1 ° ~ 3 °, under special circumstances can be increased appropriately.

2. Mold surface treatment

• Titanium Nitride (TiN) plating
  Increase the hardness of the mold surface, reduce friction, and improve the release effect.
• Use of mold release agents
  On the premise of not affecting the performance of the products, professional high temperature release agent can be used.

In short, the design and manufacture of PEEK molds need to consider the special nature of the material, from the mold material selection, design points, processing technology to safety and environmental protection, etc., all need professional knowledge and experience. Techeng Technology is a professional PEEK mold manufacturer, providing PEEK mold design and injection molding.