Measures to reduce thermal deformation of machine tools.

Under the influence of internal and external heat sources, various parts of the machine tool will have different degrees of thermal deformation, so that the relative motion relationship between the workpiece and the tool will be broken, which is also the decline of the machine tool. For CNC machine tools, because the whole processing process is controlled by computational instructions, the influence of thermal deformation is more serious. In order to reduce thermal deformation, the following measures are usually adopted in the structure of CNC machine tools.
1. Reduce fever
The main heat source of thermal deformation in machine tool should be separated from the main engine as far as possible.
2. Control the temperature rise
After taking a series of measures to reduce the heat source, the thermal deformation will be improved. However, it is very difficult or even impossible to completely eliminate the internal and external heat sources of machine tools. Therefore, the temperature rise must be controlled by good heat dissipation and cooling to reduce the influence of heat source. The most effective method is forced cooling in the heating part of the machine tool, or heating in the low-temperature part of the machine tool, so that the temperature of each point of the machine tool tends to be the same, which can reduce the warpage caused by the temperature difference.
3. Improve the machine tool mechanism
Under the same heating condition, the machine tool mechanism also has a great influence on the thermal deformation. For example, the single column mechanism used in CNC machine tools may be replaced by the double column mechanism. Because of the symmetry between the left and the right, the deformation of the main axis of the double column mechanism in other directions is very small except for the translation in the vertical direction, and the movement of the axis in the vertical direction can be easily compensated by a coordinate correction.
For the spindle box of CNC lathe, the thermal deformation of spindle should occur in the vertical direction of cutting tool. This can minimize the influence of spindle thermal deformation on machining diameter. In the structure, the distance between the spindle center and the spindle to the ground should be reduced as much as possible to reduce the total amount of thermal deformation. At the same time, the temperature rise of the front and back of the main axle box should be consistent to avoid the inclination of the spindle after deformation.
The ball screw in CNC machine tools often works under the conditions of large expected load, high speed and poor heat dissipation, so the ball screw is easy to heat. The result of ball screw hot production is serious, especially in the open-loop system, it will make the feed system lose the positioning accuracy. At present, some machine tools use pre drawing method to reduce the thermal deformation of the lead screw. For the thermal deformation which can not be eliminated by the above measures, it can be corrected by the compensation pulse sent by the numerical control system according to the measurement results.