The rake angle is one of the important parameters of the cutting tool, and its influence on the cutting process is mainly manifested in the following aspects:
- It affects the cutting deformation and cutting force during the cutting process. Under the premise that other conditions remain unchanged if the rake angle is increased, then the cutter head is sharp, the cutting is easy and labor-saving, and the chips are easy to flow out, which can not only reduce cutting deformation, cutting force and cutting power but also help improve the quality of the machined surface.
- It affects the strength, heat conditions and force properties of the insert tip. As the increase in the rake angle, the decrease in the strength of the cutter head, the deterioration of the heat dissipation conditions in the cutting zone, the increase in the cutting temperature, the increase in wear, the decrease in tool durability, and even the chipping.
The selection strategy of tool rake angle
According to the above analysis, the rake angle should be selected under the premise of ensuring processing quality. It is supposed that the cutting edge is sharp, easy cutting and labor-saving, and it is also hoped that the strength of the cutter head and the heat dissipation conditions can be taken into account to improve the durability of the cutter. Therefore, under certain processing conditions, there must be a reasonable rake angle.
- The higher the strength and hardness of the workpiece material, the greater the cutting force and the higher the cutting temperature. In order to ensure the strength of the tooltip, improve the heat dissipation conditions, and slow down the wear of the tool, a smaller rake angle should be selected. For example, the rake angle of normalized high carbon steel is usually 10°~15°. The better the plastic toughness of the material, the greater the friction. In order to reduce friction and avoid buildup, a larger rake angle is generally used. For example, a rake angle of 20°~25° is often used for processing low carbon steel. When processing brittle materials, the cutting edge is concentrated and bears the impact force, and even chipping occurs. In order to improve the strength and heat dissipation of the cutting edge, the rake angle of the tool is usually smaller than when processing plastic materials, such as gray cast iron. The angle is 5°~15°.
- Different materials for cutting tools have different performance characteristics, and the selected rake angles are also different. HSS has higher strength and better toughness than cemented carbide inserts. Therefore, the rake angle is 5 to 10 larger than that of cemented carbide tools; ceramic materials are more brittle than cemented carbide. In order to ensure the strength of the cutting edge, the rake angle is selected Should be smaller than cemented carbide tools; CBN tools are more brittle and usually use negative rake angles for cutting.
- In rough machining and intermittent machining, due to the relatively large vibration and impact, the strength of the cutter head is mainly considered, and a smaller rake angle is usually selected; in finishing machining, the processing quality is mainly considered, and a larger rake angle is usually selected.
- When the rigidity of the processing system is poor, or the power of the machine tool is small, in order to reduce the cutting force, a larger rake angle should be selected.
- For CNC machining or automated machining, in order to reduce tool wear, ensure tool durability and work stability, the rake angle should be selected to a smaller value; generating tools or forming tools, in order to increase the strength of the tool tip and prevent blade distortion, the rake angle is often smaller, even 0 degrees.
I believe you have a certain understanding of the analysis of the influence of the tool rake angle on the cutting process and the selection strategy. Later, we will analyze the clearance angle as well, so stay tuned to our new article “What Effect Does the Clearance Angle Have on CNC Cutting?“.