Research On Key Technologies Of Fiber Bragg Grating Measurement For The Thermal Deformation Of Machine Tools

With all kinds of new technologies have been widely used in precision finishing,the technology in precision and accurate measurement has a rapid development.At the same time,people also pay more attention to the micro displacement measurement methods,such as the precision measurement in machine tools spindle offset which caused by thermal deformation in machine tools.The measurement technology of thermal deformation in machine tools,the key to determine the error compensation precision in machine tools,is also an important factor to improve the machining accuracy of the machine tools.The thermal error measurement,essentially to measure thermal displacement,the scale of which is too small in magnitude,usually measured by micro displacement sensor.And the FBGs which has unique advantages can be used in thermal error measurement.Therefore,the research for displacement micro measurement method based on fiber grating,exploring for online monitoring technology on small deformation and micro displacement in all kinds of large-scale equipment,is of great significance.Firstly,this paper made the simulation and experiment analysis to the Longmen heavy-duty CNC milling machine with fixed beam which model is XK2755.Doing the simulation in the environment of ANSYS workbench: setting up a sine function to simulate the change of temperature,to do the thermal transient analysis and thermal transient stress analysis in the stationary state and the idling state of the machine tool.After that establishing a test bench for measuring the machine tools spindle offset,and then testing the trend of the spindle offset and maximum offset.Then,a micro displacement measurement method based on Fiber Bragg grating sensing is designed,and the main content is designing the FBG micro-displacement sensor,aiming at measuring the thermal error of machine tools.The resolution and range of the sensor have been fixed according to the magnitude of the spindle offset,thus establishing the mechanical models of the three sensors,and determining the size and material of the sensors.After that the first thing is to do the simulation and calibration experiment of forming micro displacement sensor in static characteristics,and from these to obtain the parameters,such as sensitivity,measuring range,linearity,hysteresis error and repeatability error,in order to prepare for the final experiment of measuring the spindle offset in machine tools;the second thing is to do simulation and experiment of forming micro displacement sensor to obtain the actual natural frequency;the third thing is to finish the temperature compensation experiment,to make sure whether the results of the compensation are obvious.Finally,doing the confirmatory experiment according to the spindle offset in the machine tools caused by the machine tool thermal error.Firstly,according to the third chapter contents which are about micro displacement measurement system based on fiber grating sensing,we designed a set of measuring system for measuring the thermal deformation of machine tools.And then setting up an experimental platform for measuring the spindle offset in machine tools at room temperature.The experimental platform is mainly composed of heavy-duty CNC milling machine,FBG micro displacement sensors,quartz rod,clamping part,limiting device,MOI demodulator,PC and LK-G80 laser displacement sensors,electric temperature sensors and so on.Using the results tested by LK-G80 laser displacement sensors as the testing standard,the thermal displacement of the machine tool,into of which converted by the measured wavelength shift,compared with the test standard.