PEEK screws possess characteristics such as heat resistance, superior wear resistance, high tensile strength, and good flame retardancy. They also exhibit the temperature resistance of polyurethane elastomers, the chemical stability of organic materials, and the moldability of thermosetting plastics. The processing of PEEK screw raw materials can be carried out through various methods such as injection molding, flame retardant processing, injection, pressing, and mechanical processing. Among these, mechanical processing has significant differences from metal composites and general rubber products in terms of thermal deformation, heat dissipation performance, ductility, and wear resistance. If not given adequate attention and operated improperly, it can result in cracking and even damage to the processing equipment.
Reasons for Material Cracking During Processing:
- Residual Stress: The inherent stress of the billet itself has not been completely eliminated, leading to cracking during processing.
- Excessive Material Removal: Using too large a material removal rate during processing can cause cracking.
- Drilling Issues: Using a large drill bit directly for drilling can cause cracking due to the high cutting speed and extrusion.
- Deep Hole Drilling: Failure to repeatedly retract the drill bit and clear chips during deep hole drilling leads to insufficient chip evacuation, causing cracking.
- Insufficient Cooling: Inadequate cooling during drilling results in heat buildup and high cutting speeds, leading to cracking.
- Feed Rate: A fast feed rate increases internal stress within the PEEK screw material, causing cracking.
- Tool Wear: Due to PEEK material’s wear resistance, the cutting edges of drill bits wear out quickly. If the drill bit is not sharpened promptly, forcing it to drill will cause cracking.
Analyzing the causes of cracking can be divided into two aspects: material and processing. If the rough machining amount of the part is large, the heat generated will inevitably release thermal stress, leading to part deformation. Especially for parts with high dimensional accuracy, it is necessary to perform an annealing process after rough machining and then finish machining to the specified dimensions. The primary function of annealing heat treatment is to improve the grain size of the part, thereby enhancing its internal cohesion and increasing its stability over a wider temperature range.
