Development Of Reliability Test Device For Precision Grating Rule

The grating ruler is a key measuring component of modern NC machine tools.Its measuring accuracy and reliability level have an important impact on the operation accuracy and reliability of NC machine tools.Therefore,improving the reliability level of domestic grating ruler is of great significance to the development of middle and highend NC equipment in China.In this thesis,the reliability test device and test technology of grating ruler manufactured by domestic manufacturers are studied.The purpose is to obtain the fault data of grating ruler in operation,provide improvement measures for grating ruler,and improve the reliability level of grating ruler made in China.In view of the fact that the current grating ruler test is only a simple air operation test and can not simulate the real working conditions,this thesis develops a reliability test device which can simulate the actual working conditions of the grating ruler.On the basis of compiling the load spectrum of its working conditions,the reliability test is carried out.The specific contents include:1.Based on the in-depth analysis of the principle and structure of grating ruler,the grating ruler is divided into three subsystems: optical,mechanical and electronic.Considering the influence and harm of environmental stress on subsystems and specific components,a fault tree of grating ruler is constructed by FTA method,and the fault of grating ruler is analyzed.According to the purpose and requirement of reliability test for complex mechanical and electrical products,the overall scheme of grating ruler test device is designed.2.The mechanical design and theoretical analysis of the grating ruler test device are carried out.After that,the parts are selected and the stiffness of the system is taken into account.The innovative proposal is to build the test system by using the two-side vertical placement of the servo platform,which improves the stiffness of the system and increases the number of grating rulers tested.The application of modal analysis to grasp the dynamic characteristics of the device lays the foundation for the subsequent formulation of stress application program.3.The velocity spectrum,temperature spectrum and humidity spectrum of grating ruler are established by fitting distribution method through collecting the load data of feed system of NC machine tool,environment temperature and humidity of machine tool.On this basis,the load spectrum test specifications and schemes of grating ruler speed program are formulated and the reliability test in laboratory is carried out,which verifies the rationality of the device.