： Research of machining center thermal error compensation
Abstract: In the process of machining, the thermal error produced by machining must be compensated. If the thermal error is not compensated, it will affect the precision of the machining surface. Machining center plays an important role in CNC machining. Therefore, the thermal error compensation research of machining center is particularly important. This paper introduces the necessity of machining center thermal error compensation and the methods of thermal error compensation, and presents the research progress of thermal error compensation of machining centers in depth.
1 Introduction
In the process of CNC machining, the machining center is the core equipment. Its machining accuracy is directly related to the accuracy of the processed parts. As the machining center completes the cutting and assembly of various parts, the machining center must carry out a series of machining process, such as turning, milling, drilling, grinding and so on. However, during the machining, the accuracy of the machining center will be affected by many factors, such as temperature changes, material properties, cutting condition, spindle runout and geometrical accuracy of each jointed points etc. Among these factors, the thermal error caused by the environmental temperature changes is an important factor which influences the machining accuracy.
2 Necessity of thermal error compensation of machining center
Thermal errors refers to the errors caused by the internal thermal expansion due to the environmental temperature changes of the CNC machining center, and it directly affects the machining accuracy of the machining center. Therefore, it is necessary to compensate for the thermal errors of the machining center. Thermal error compensation is to collect the relationship between temperature and machining errors, and then analyze and process the data to obtain the corresponding temperature compensation parameters. This compensates for the thermal errors of the machining center.
The thermal error of the machining center is mainly concentrated in the three axes (X, Y and Z) of the machining center, but it is important to note that each axis has its own thermal characteristics. With the increase of the temperature, the thermal expansion of each axis is not the same. Therefore, in the process of thermal compensation, it is necessary to carry out separate compensation for each axis.
3 Methods of thermal error compensation
There are two methods of thermal error compensation for machining center: manual thermal compensation and real-time thermal compensation. The manual temperature compensation is relatively simple. After the detection of temperature, the values of temperature compensation parameters are determined according to the theoretical data, and then the temperature compensation is completed by manual setting. The real-time thermal compensation is to compensate for the thermal error through real-time temperature detection and self-adjusting. This method can compensate for the thermal error in real time, which can greatly improve the machining accuracy.
4 Research progress of thermal error compensation of machining center
In order to solve the problem of thermal errors and improve the machining accuracy of the machining center, many research institutions at home and abroad have carried out a lot of research on the thermal error compensation of the machining center.
Huang Yongjin et al. [1] studied the thermal error model of the machining center, established a three-dimensional thermal error model, and obtained the linear thermal error function formula. The research provides a reliable basis for the implementation of thermal compensation. At the same time, Turani et al. [2] carried out a statistical analysis on the thermally induced errors of the machined parts by machining center. The results showed that the maximum error tolerance was ±0.5 mm, and manual temperature compensation on the CNC machine tool was recommended.
Kern et al. [3] used the SARD (Power Factor Residual Group Subspace Descriptor) method to analyze the error sources of the machining center, and it was found that the environmental temperature change is one of the error sources. Pinnelli [4] proposed a simulation-tuning ten-factor model for machining centers to simulate the temperature-induced error sources. Through this model, the temperature compensation parameters can be quickly calculated, and it provides a reference for the compensation of thermal errors of the machining center. Liu et al. [5] proposed a temperature compensation method based on fast Fourier transform to reduce the thermal errors of the machining center. The results show that this method can effectively reduce the thermal errors of the machining center and improve the machining accuracy.
5 Conclusion
Thermal errors are an important factor that affects the machining accuracy of the machining center. It is very important to carry out thermal compensation to ensure the machining accuracy of parts machined by the machining center. This paper has introduced the necessity and methods of thermal error compensation, and has given the research progress of thermal error compensation of machining centers at home and abroad.
