Real-time Compensation Technology For Thermal Error Of Precision Horizontal Machining Center

Precision horizontal machining center is a class of high-grade CNC machine tool products.Because of its high degree of automation and intelligence,flexibility and versatility,it is the key equipment to machine box precision parts in aerospace,automobiles,ships,machine tools and other major areas.With the development of CNC machine tools towards high speed and high precision,the influence of thermal error on the machining accuracy of machine tools is more and more obvious.This paper will focus on the problems of thermal error measurement and compensation.The main ways to reduce the thermal error of machine tools can be divided into three categories: thermal balance design,active control of temperature field,and thermal error compensation.The three methods are usually used comprehensively in actual engineering application.In this paper,the thermal deformation of the precision horizontal machining center is studied to satisfy engineering requirements.A method of thermal deformation measurement,modeling and compensation according to major structure parts' deformation is presented and verified to improve the accuracy and stability of the machine.In terms of thermal error modeling,a thermal error modeling method for machine tool workspace based on deformation of structural parts is proposed,and the mapping relationship between thermal deformation of structural parts and thermal deformation among tool and workpiece of the machining center is established.According to this method,the deformation test lines of large structural parts of a precision horizontal machining center such as bed,column,slide seat are established,and the simulation analysis of thermal deformation of structural large parts is carried out under various temperature conditions,to get the expression between the thermal deformations of the guide in three directions and the deformations of the test lines of the large structure parts.The error mapping model of guide plane and motion pairs-workspace is established by multi-body dynamics.Based on the above model,the sensitivity of each error to the thermal deformation error in the working space of the machine tool is analyzed to provide support for the adjustment of the dynamic relation.In terms of thermal deformation testing and compensation,the thermal deformation testing device of machine tool structure is developed,and the real-time compensation software for thermal error of machine tool is developed using the offset method of the origin of external coordinates.Based on the thermal error modeling for machine tool workspace in view of deformation of structural parts,the actual structure test line device are designed using the high precision non-contact displacement sensor and the carbon fiber bar.The bars are used as the deformation base and the sensors are fixed on structure.By testing the displacement between the carbon fiber bar and displacement sensor,the real-time deformations of the structure part test lines are obtained.Considering the engineering use,the sensors of each structural part are integrated and further serial connected to build the integrated thermal deformation test system.According to the established thermal error model and integrated thermal deformation testing system,the real-time compensation software for thermal error of machine tool was developed,and the real-time calculation and compensation platform is established.The established system and platform can measure the value of the displacement sensor on the structure parts in real time,and the compensation data obtained by real-time calculation based on the model will be input into the numerical control system,and the external coordinate origin offset method is adopted to achieve continuous real-time compensation.In terms of the rapid detection of thermal error,a multi-accuracy comprehensive detection method including the diagonal of the workspace,the diagonal of the surface and the linear axis is proposed,and the effectiveness of the proposed real-time thermal error compensation method is verified by experiments.The error items detected by this method include single linear axis error,two-axis linkage error and three-axis linkage body diagonal error.The error items are diverse,and the combination of each detection line can basically cover the working space of the machine tool.At the same time,the test speed is fast and suited for engineering use.With high precision laser tracker test validation of the body diagonal and surface diagonal and single linear axis,it shows that the thermal error compensation effect of working space can reach 35?50%.The thermal error compensation method mentioned above has a good real-time performance,which does not need to install a large number of temperature sensors on the machine,and the test line and displacement sensors are installed in the periphery of the large structure,far away from the processing area,and the working environment of the sensors is good,with good accuracy and reliability.This method is convenient for engineering application,can effectively reduce the thermal error,improve the machining accuracy and thermal stability of the machine,and has important significance engineering application value.