PEEK machining accuracy in injection molding: Tips & Tricks

Polyetheretherketone (PEEK) - is a high performance thermoplastic polymer that has become popular because of its unique mechanical properties, chemical resistance and heat resistance. These characteristics make it the best option for high-tech applications such as aerospace, medical, automotive and oil and gas. However, working with PEEK material requires specialized skills and techniques, especially when it is injection molded. This process can present a significant challenge for engineering and technology professionals. In this blog, we will review the key aspects of handling PEEK material and provide tips for a successful injection molding process using it.

What makes PEEK so unique?

Before getting into the injection molding process, it is important to understand why PEEK is such a sought-after material:
PEEK polymer has one of the highest melting points among thermoplastics, around 343°C. This provides it with resistance to high temperatures, which is critical for components that function in extreme environments.

Physical resilience: This material has outstanding physical characteristics such as high tensile strength and stiffness. This makes it possible to use PEEK in parts that are subjected to significant mechanical stress.

Chemical resistance: PEEK is resistant to aggressive chemical environments, making it an optimal material for chemical and highly corrosive applications such as oil and gas.

Compatibility with the body: This material is widely used in the medical field because of its compatibility with human tissue, making it ideal for creating implants.

Preparation for PEEK injection molding

Working with PEEK requires special attention at all stages of production, from the preparation of the material to the final finishing of the product.

1. Drying of material

PEEK, like many other thermoplastics, has hygroscopic properties, which means that it can absorb moisture from the environment. Moisture can adversely affect the injection molding process, leading to defects such as porosity and lack of strength. Consequently, a thorough drying process must be carried out before proceeding with PEEK molding. Drying is usually carried out at a temperature of about 150°C for 3-4 hours. Equipment selection
PEEK molding requires equipment that can withstand high temperatures. The melting point of PEEK is approximately 343°C, which requires screws and cylinders that are resistant to thermal deformation and wear. To prevent overheating and uneven melting, it is recommended to use equipment with a precise temperature control system.

Mold selection
Mold for PEEK injection molding requires quality materials that can withstand high temperatures and pressures. Heat-treated steel molds with titanium nitride coating ensure durability and precision when working with PEEK.
PEEK injection molding process
Melting temperature control
Is of critical importance when carrying out the PEEK molding process. If the temperature is not high enough, the material may not melt sufficiently, which can cause defects on the surface of the product. On the other hand, higher temperatures can lead to material degradation. The optimum melting temperature is 360-400°C, but this value can vary depending on equipment configuration and product geometry.

Pressure for injection
PEEK requires higher injection pressure due to its high viscosity. Typical injection pressures range from 1000 to 2000 bar. However, excessive pressure can cause equipment wear and mold deformation. Therefore, it is recommended to customize the pressure for each individual product and equipment.

3. Injection speed

Injection speed also plays an important role in the molding process. Insufficient mold filling speed can cause uneven material distribution and defects such as underfills. Optimal injection speed ensures uniform mold filling without overheating the material.

4. press mold temperature

The mold temperature of the press plays a key role in ensuring high casting quality. It is recommended to keep the mold temperature between 160 and 200°C. This improves material flow, reduces internal stresses and improves the surface quality of the product.

5. Cooling time

The time required to cool down PEEK is usually longer compared to other thermoplastics due to its high melting point and low thermal conductivity. The cooling time should be optimized for the product wall thickness and shape geometry. Insufficient cooling can lead to deformation and reduced product accuracy.

Possible defects in PEEK casting and their elimination

Working with PEEK requires special attention to detail, as the material is prone to develop some defects if not processed properly.

1. porosity

The appearance of porosity can be caused by moisture in the material or by incorrect injection parameters. To solve this problem, carefully dry the material and observe the injection pressure.

2. Deformation

Deformation can occur due to uneven cooling or insufficient holding pressure. The solution is to adjust the cooling parameters and increase the holding pressure.

3. underspills
Underfills occur when the mold does not fill completely. This may be due to insufficient injection pressure or low material temperature. Increasing the injection pressure and melting temperature can help solve this problem.

Features of working with engineering plastics: PEEK vs other materials

Comparison of PEEK with other engineering plastics such as PPSU, LCP и PVDF, identifies the following key points:

• Melting point: PEEK has a significantly higher melting point than PPSU or LCP, making it the best choice for high temperature applications.
• Mechanical strength: PEEK outperforms other thermoplastics in strength and stiffness, making it ideal for components subjected to high mechanical stress.
• Chemical resistance: PEEK shows excellent chemical resistance in aggressive environments, while other plastics can degrade when exposed to chemicals.

Advantages of using PEEK in injection molding

Durability: Components made of PEEK are highly resistant to abrasion and chemical agents, which helps to extend the life of the product.

Resistance to high temperatures: Due to its ability to withstand high temperatures, PEEK is ideal for use in high temperature and thermal stress applications.

Strength: This material has high mechanical strength, making it an optimal choice for aerospace and medical applications.

Versatility:
PEEK can be used in a variety of industries including automotive, oil and gas, and electronics.

PEEK injection molding - is a complex but very profitable process that requires attention to detail and the use of the right technology. Correct material preparation, monitoring of process parameters and selection of appropriate equipment are the main factors for successful work with this unique material. PEEK - is an outstanding thermoplastic with unique properties that make it an excellent material for advanced applications. If the guidelines and process requirements are followed, it is possible to achieve excellent results when producing PEEK parts by injection molding.