It is better to equip ISO 50 spindle with short tool overhang for machining titanium. However, the current situation is that most machine tools are equipped with IS0 40 spindle. If the strength of the machine tool is too strong, it is impossible to keep the tool sharp for a long time. In addition, how to clamp the parts with complex structure is also a thorny problem. However, the biggest challenge actually comes from vibration and heat.
Sometimes, the cutting process in titanium processing must be used for full slot milling, side cutting or contour milling, which will cause vibration and form poor cutting conditions. Vibration will cause the blade to break, the blade to damage and produce many unforeseen results. Therefore, when setting the machine tool, we must pay attention to the principle of improving stability to reduce the occurrence of vibration. An improvement measure is to adopt multi-stage clamping to make the parts closer to the spindle to help offset the vibration.
A lot of heat will be produced in the process of titanium processing, resulting in the temperature rise. Unfortunately, high temperature will affect the cutting performance of the tool, but it will not affect the hardness of the workpiece. Titanium can still maintain extremely high hardness and strength at high temperature, and even work hardening will occur, which makes processing further difficult and is not conducive to some subsequent cutting processes. Therefore, choosing the best indexable blade brand and groove shape is the key to the success of machining. According to past experience, fine grain uncoated blade brand is very suitable for titanium processing; Today, blade grades with PVD titanium coating have greater advantages in improving cutting performance.
Accuracy, conditions and correct cutting parameters
The axial and radial runout accuracy of the tool requires special attention. For example, if the blade is not correctly installed in the milling cutter, the surrounding cutting edge will be extremely easy to damage. In addition, the service life of the tool will also be greatly reduced due to the wrong manufacturing tolerance of the tool, tool wear, spindle wear and tool handle defects. In all cases of poor processing performance, the proportion caused by the above factors accounted for 80% in total.
Compared with the positive rake groove tool that most people like, the tool with slightly negative rake groove can remove material with a higher feed, and the feed per tooth can reach 0.5 mm. But this requires that the machine tool is very solid and the clamping is extremely stable. In addition to insert milling, the main deflection angle of 90 degrees should be avoided as far as possible, which can improve the stability of cutting, especially in the case of shallow cutting depth. In deep cavity milling, it is an ideal way to use a tool with variable length through the tool handle, and its processing effect is better than using a single length of long tool in the whole process.
When milling titanium, it is required to accurately calculate the feed rate of each tooth of the tool, so that it is not lower than the minimum feed rate - usually 0.1 mm. In addition, you can also reduce the spindle speed to achieve the initial feed rate, which is also conducive to improving the tool life. If the minimum feed per tooth is used and the spindle speed is too fast, the impact on the tool life can be as high as 95%. Once the stable working condition is established, the spindle speed and feed rate can be increased accordingly to obtain the best performance.