Dynamic Characteristic Analysis Of Electric Spindle System Of Precision Grinder

With the development of automobile industry,higher requirement on the processing quality of the camshaft has been put forward,camshaft grinding is a non circle grinding,which not only has large machining allowance and high precision,but also the material is difficult to grind.Therefore,the camshaft grinding technology has a certain restricts the development of the automobile industry.The key of the camshaft grinding technology is the precision grinding machine,and the core component of precision grinder is electric spindle system,which the dynamic performance directly determines the grinding precision of the camshaft,the hybridbearing is an important supporting part of the main shaft unit,its thermal deformation of the spindle unit caused by the oil film temperature rise greatly affects the spindle rotation precision.In order to improve the grinding precision,efficiency and reliability of the grinding machine,this paper made the following research on the electric spindle system of precision grinder:(1)According to the technical parameters and working conditions of the grinding machine,calculating the grinding force,designing and calculating the main structure of the electric spindle system.The motor is selected and the spindle diameter,diameter,overhang and span are determined,the bearing type is selected and the stiffness of the bearing is calculated.The mechanical structure and working principle of the electric spindle system are analyzed.(2)Establishing the differential equation of motion of the electric spindle system by Lagrange method.The finite element model of rotor-bearing is established by using ANSYS parametric design language,and has carried on the modal analysis of the spindle system,getting the five order natural frequencies and mode shapes of the spindle system,then calculate the critical speed,the influence of different boundary support on the natural frequency of the electric spindle system is studied.The harmonic response analysis is carried out based on the modal analysis,and the spindle system dynamic stiffness is calculated.The electric spindle system was improved by adopting three supporting structure,which improves the dynamic performance of the electric spindle system,then the main measures to improve the dynamic performance of the electric spindle system are summarized.(3)The oil film temperature field of the front and back hybridbearing of the electric spindle system is simulated by using computational fluid dynamics software FLUENT,and the oil film temperature field distribution of the front and back bearings is obtained.Thermal deformation of the spindle unit analyzed by using of Workbench software,the radial thermal deformation of the front end of the spindle is obtained,and the influence of the front end of the spindle radial thermal deformation on different revolutions are studied.(4)The experimental modal analysis of the electric spindle system of precision grinding machine is carried out by using the hammering method,and the frequency response function of the spindle system is obtained by single point excitation,the natural frequency and the damping ratio of the electric spindle system are obtained,and the correctness of the finite element simulation results is verified.The actual temperature rise of the front and back hybridbearing of the electric spindle system was measured by infrared thermometer in the operation process,the size of the thermal deformation of the actual spindle unit was calculated and compared with the theoretical results.