Trend of thermal deformation of various machine tools and its influence on machining accuracy  
(1) Thermal deformation of turning, milling, drilling and boring machine tools the main heat source of such machine tools is the spindle box. The heat transmitted to the lubricating oil due to the friction and heating of the gears and bearings in the spindle box will increase the temperature of the spindle box and its connected bed or spindle and produce large thermal deformation.  
(2) Thermal deformation of grinding machine tools.  
(3) Thermal deformation of large machine tools. In this case, shape error and position error will occur on the workpiece surface after machining.  
(4) Thermal deformation of CNC machine tools and machining center machine tools. Machining center machine tools, which process workpieces in multiple aspects and processes without changing the clamping conditions of workpieces, have high speed, large internal heat source, short heat dissipation time, and do not allow large thermal deformation. Therefore, corresponding measures must be taken to prevent thermal deformation of CNC machine tools and machining center machine tools.  
 
The main reason for the thermal deformation of machine tool is the heating of heat source. Reducing the heating amount of heat source is one of the main measures to reduce the thermal deformation of machine tool.  
 
Improve the quality of rolling bearings. Change the lubrication conditions and assembly quality of main bearing and transmission bearing. The temperature rise of mechanical bearing mainly depends on the radial load and friction coefficient. In addition to changing the lubrication conditions of the bearing, dynamic pressure oil film bearing and hydrostatic bearing can also be used, which may reduce the friction coefficient and reduce the heating capacity of the bearing.  
 
Generally speaking, the design of the oil tank is reasonable and the natural heat dissipation of the oil tank can meet the oil temperature control requirements of the oil tank. However, for precision machine tools, the oil temperature of hydraulic components and lubricating oil should be strictly controlled. Sometimes constant temperature is required to maintain the normal working accuracy of the machine tool.  
 
In this case, it is necessary to control the oil temperature. In addition to blowing by fan or refrigerator, serpentine cooler or tubular cooler can also be arranged in the oil tank to take away the excess heat with cooling water. The original air-cooled motor can be cooled by hydrogen and helium. Because their thermal conductivity is 510 times higher than that of ordinary gas, the cooling effect is much better by using hydrogen and helium. Improve the surface finish of all parts of the machine tool. Painting, oxidation and surface treatment can improve the heat absorption conditions of the surface, so as to control the influence of various heat sources.  
 
To sum up, the reasonable structural design and process measures of the machine tool can be used to control and prevent the influence of thermal deformation of the machine tool on the machining accuracy. The other way is to innovate in the use of materials for all parts and components of machine tools. Special materials with small linear expansion coefficient such as granite, light alloy and fine ceramics can be used to manufacture basic supports such as machine bed and column.  
 
When using glass ceramics to make precision machine tool spindle, it is an ideal material. Because of this special material, the vibration attenuation is good. Good thermal stability, stable size and easy to obtain materials. Therefore, the influence of thermal deformation of machine tool on machining accuracy can be reduced. In addition, the automatic compensation technology of machining error is another way to improve machining accuracy.  
 
The influence of machine tool thermal deformation on machining error can be controlled by comprehensively using sensing detection technology, size prediction and software compensation of automatic control method.