Machining Techniques
CNC machining of PEEK involves several key factors, including the selection of cutting tools, feed rates, and coolant type. Carbide tooling is generally recommended for machining PEEK, as it offers better wear resistance and maintains its sharpness over time. High-speed steel (HSS) tooling is also suitable for machining PEEK, but it may not last as long as carbide tooling. Feed rates for PEEK should be low and controlled, to avoid excess heat buildup that can cause melting or deformation. Additionally, coolant should be used during machining to help dissipate heat and extend tool life. However, it is important to note that water-based coolants should be avoided, as they can cause the material to swell or warp.
Tool Geometry
The geometry of the cutting tool is a critical factor when machining PEEK. Flat end mills are the most commonly used tool for PEEK machining, as they provide a stable surface for the material to be cut. However, ball-nose end mills can also be used for contour milling and profiling, as they can create smooth, curved surfaces. When selecting a tool for PEEK machining, it is important to consider the number of cutting edges, as well as the material and coatings used in the tool's construction. Multi-flute tools can provide better chip evacuation and improve surface finish, while diamond-coated tools can increase tool life.
Cutting Parameters
Proper control of cutting parameters is necessary to achieve optimal machining results when working with PEEK. The cutting parameters that should be considered include speed, feed rate, cut depth, and engagement angle. Speed should generally be kept low, as high speed can generate excessive heat and cause thermal damage to the material. Feed rate should be controlled to maintain a constant chip load on the tool and avoid overheating. Cut depth should be kept shallow, to prevent the build-up of heat and reduce the risk of cracking. The engagement angle is also critical, as it determines the amount of chip load and directly impacts tool life. When working with PEEK, it is recommended that the engagement angle be kept below 90 degrees, to limit tool wear and prolong tool life.
Material Handling
In addition to machining factors, proper material handling is also critical in achieving quality results when working with PEEK. PEEK is prone to absorbing moisture, and this can cause dimensional changes in the material that can affect machining quality. Therefore, it is important to store the material in a dry environment and avoid exposing it to moisture or high humidity. Additionally, PEEK should be allowed to acclimate to the environment in which it will be machined before any cutting takes place.
