Explore the key parameters of CNC turning of titanium alloy materials

To explore the key parameters of CNC turning titanium alloy materials, one can start from aspects such as the geometric parameters of the cutting tool, cutting parameters, the use of cutting fluid, and other parameters. The following is a detailed introduction:

Tool geometry parameters

The rake Angle: The contact length between the titanium alloy chip and the rake face is short. When the rake Angle is small, it can not only increase the contact area of the chip, preventing the cutting heat and cutting force from being overly concentrated near the cutting edge and improving the heat dissipation conditions, but also strengthen the cutting edge and reduce the possibility of chipping. When performing rough machining, the rake Angle can be selected from 3° to 7°. When performing fine machining, the rake Angle can be selected at 10° to 15°.

Relief Angle: The machined surface of titanium alloy has a large elastic recovery and severe cold hardening phenomenon. Using a large relief Angle can reduce the friction, adhesion, bonding, tearing and other phenomena caused to the rear tool face, thereby reducing the wear of the rear tool face. The rear Angle is usually selected to be 8° to 15°.

Main deflection Angle and secondary deflection Angle: When cutting titanium alloys, the cutting temperature is high and the tendency of elastic deformation is large. Under the condition that the rigidity of the process system permits, the main deflection Angle should be reduced as much as possible to increase the heat dissipation area of the cutting part and reduce the load per unit length of the cutting edge. Generally, 30° is adopted, and 45° is taken during rough machining. Reducing the secondary deflection Angle can enhance the tool tip, which is beneficial for heat dissipation and lowering the surface roughness value of the machined surface. Generally, it is taken as 10° to 15°.

Edge inclination Angle: Due to the hard skin and uneven surface structure of the blank, the cutting edge is prone to chipping during rough turning. To enhance the strength and sharpness of the cutting edge, the sliding speed of the chip should be increased. When rough turning, the cutting edge inclination Angle is generally taken as -3° to -5°, and when finish turning, it is taken as 0°.

The radius of the tool tip arc: When cutting titanium alloys, the tool tip is the weakest part, which is prone to chipping and wear. Therefore, the arc of the tool tip needs to be ground out. During rough machining, the radius of the tool tip arc is 0.5 to 1.0mm. When performing fine machining, the radius of the arc at the tool tip is 0.3 to 0.5mm.

Negative chamfering: It can ground a negative chamfering of 0.05 to 0.1mm, enhancing the strength of the cutting edge.

Cutting parameters

Cutting speed: The cutting speed has the greatest impact on the durability of the tool. It is best to ensure that the tool operates at the optimal cutting speed with the least relative wear. Due to the poor thermal conductivity of titanium alloys, the cutting speed should not be too high. The optimal cutting temperature for high-speed steel tools when cutting titanium alloys is approximately 480℃ to 540℃, and for cemented carbide tools, it is about 650℃ to 750℃. During rough machining, the cutting speed can be selected as 25 to 38m/min or 40 to 50m/min. During finish machining, the cutting speed can be selected at 50 to 75m/min.

Feed rate: The feed rate has a relatively small impact on the durability of the cutting tool. Under the condition of ensuring the surface roughness of the machined surface, a larger feed rate can be selected. However, if the feed rate is too small, the tool will cut within the hardened layer, increasing tool wear. At the same time, extremely thin chips are prone to spontaneous combustion at high cutting temperatures. Therefore, a feed rate less than 0.05mm/r is not allowed. Generally, the feed rate is taken as 0.1 to 0.3mm/r. During rough machining, it is 0.2 to 0.5mm/r, and during finish machining, it is 0.1 to 0.15mm/r.

Cutting depth: The cutting depth has the least impact on the durability of the tool. Generally, a larger cutting depth is selected. This not only prevents the tool tip from cutting within the hardened layer, reducing tool wear, but also increases the working length of the cutting edge, which is conducive to heat dissipation. Generally, the cutting depth is taken as 1 to 5mm. During rough machining, it is 3 to 5mm, and during finish machining, it is 0.2 to 0.5mm.

Use of cutting fluid

Type of cutting fluid: Anti-rust emulsion or extreme pressure emulsion can be used for cooling and lubrication, or high-pressure and high-flow cutting fluid can be adopted to ensure the thermal stability of the processing process and prevent surface deformation of the workpiece and tool damage caused by excessive temperature.

The function of cutting fluid: Cutting fluid can play a role in cooling, lubricating and cleaning, which helps to improve the processing quality and tool life. When using cutting fluid, the cutting speed can be appropriately increased.

Other parameters

The radius of the bottom arc of the chip-breaking groove: When turning, negative chamfering is adopted. The radius of the bottom arc of the chip-breaking (rolling) groove can be taken as 6 to 8mm.

The quality of tool grinding: The quality of tool grinding is of great significance for enhancing their durability. Hard alloy cutting tools should be ground with diamond grinding wheels. When cutting, the cutting edge must be sharp. The surface roughness Ra value of the front and rear cutting faces should be less than 0.4μm, and there should be no tiny notches on the cutting edge part. After the cutting tool is ground, its durability can be increased by 30%.