Peek Injection and PEEK Parts
Peek injection is an alternative method to traditional injection molding for high-performance plastics like poly ether ketone (PEEK). This method uses a photosensitive resin mould that has lower cost, shorter production cycle and no waste of the injection material during the process. Using this method, it is possible to make individualized PEEK parts that have good mechanical properties.
PEEK is a thermoplastic with good chemical resistance and is often used in oil and gas and aerospace applications. It has a high melting point, good fluidity and can be easily processed in a variety of ways such as extrusion, 3D printing and injection molding. It can also be shaped into complex shapes by heat-forming and is FDA compliant for medical use. However, PEEK is more expensive than other common plastics.
Injection molded PEEK parts are often susceptible to defects such as silver streaks, pores, weld lines and warpage. These defects occur due to improper injection pressure, temperature and mold design. To reduce the occurrence of these defects, it is necessary to optimize the injection process. Injection pressure must be moderate, and a back pressure must also be applied to the holding cylinder to ensure that PEEK is injected into the mold properly.
To reduce the occurrence of silver streaks, it is essential to avoid direct contact between the melt and air. If the sprue sleeve at a low temperature is in contact with the injection molding machine nozzle for too long, the temperature of the PEEK will drop to its melting point and the molten material will rapidly solidify. This can cause the sprue sleeve to break off from the nozzle and lead to cold material defects in the product.
Another way to reduce the occurrence of these defects is to add fillers such as glass fiber or carbon fiber. This will increase the strength of the product and reduce shrinkage. However, too much filler can create warpage and other problems during the injection molding process. In addition, it is important to monitor the temperature of the melt and the injection nozzle during the injection process. A high injection temperature can cause the sprue to become blocked by the nozzle or the nozzle to become clogged by the melt.
The dimensional accuracy of the injection molded PEEK part is critical for its function. To ensure that the part has proper dimensional tolerances, it is essential to use a quality injection molding machine with accurate temperature control. To achieve the best results, it is recommended that the injection molding temperature be set to 160-190°C / 320-374°F. The injection nozzle should be set to a position that is far enough from the gate to prevent a flow delay, which can lead to warping. In addition, a properly designed gate is essential to maintain proper crystallization and minimize warping. The gating system should be designed to allow the PEEK to reach the mold surface without forming air pockets that can result in poor dimensional accuracy.