Study On Thread Hard Whirling Technology For Ball-screw Shaft Based On Process Monitoring

Forming mechanism and process monitoring technology of thread hard whirling process for the ball-screw shaft with material of hardened GCr15 are studied and applied to process prediction and optimization.A series of key thread hard whirling technologies for ball-screw shaft have been worked out,such as tool geometry design,tool setting design,tool material choosing,tool breakage prediction,and machining accuracy prediction.All the results in this paper are valuable for high efficiency and high accuracy of thread hard whirling,and bring important technical supports for in-process monitoring and intelligent manufacturing of thread hard whirling.Above all,The influence of rotation diameter of tool tip,thread profile parameters of machined ball-screw shaft and tool pan install angle on forming accuracy of thread hard whirling is analyzed.A design method of tool profile and tool setting for thread hard whirling is proposed for profile error control of the gothic groove on ball-screw shaft,which is based on the contact line theory between conjugate surfaces.Parameters of cutting lay in thread hard whirling process of ball-screw shaft are geometrically studied.Surface integrity of different areas in machined helical surface and cutting edge conditions in machining process are mathematically discussed and verified by hard whirling test.The cutting edge area of cut-in breakage is confirmed,which establishes foundation for improvement of whirling tool performance.And then,a cutting force measuring system for individual tooth in thread whirling is developed using a triaxial piezoelectric force sensor of voltage output type.A cutting force prediction model of thread whirling is developed and verified with the effect of shearing and ploughing.After analysis of cutting force of individual whirling tooth,the cutting edge area of cut-out breakage is confirmed.Software of status data access for thread whirling machine tool are developed based on the OPC communication technology in open CNC system,which provides an important technical means of process monitoring and prediction.Thirdly,through the displacements monitoring of servo motors in thread hard whirling process,the evaluation method and data processing method of machine tool kinematic error are discussed,and the linear influence of workpiece revolution speed on machine tool kinematic fluctuation error is revealed.Through the torque monitoring of follow rest driving motor,a reasonable coefficient of workpiece fasten force is suggested.Through the cutting forces monitoring of individual whirling tooth,the stiffness of toth system is checked out,and the cutting vibration type of thread hard whirling process is identified.After establishing the regression equation of triaxial cutting forces,a method of cutting vibration control is suggested through cutting parameters.Once more,comparative thread whirling experimental investigations using PCBN tools about various tool materials and tool cutting edges are performed.Based on the study of tool failure mode and tool wear-resisting property,the chief cutting edge area of tool wear is confirmed.Resonable tool material and cutting edge of PCBN tool are suggested,and cutting parameters for different accuracy requirement of ball-screw are recommended.A method of tool breakage prediction for thread hard whirling process is proposed on the base of status data of machine tool.Based on monitoring signals from current cycle of servo motor in CNC system,a predicton method of tool breakage for thread hard whirling is proposed.Finally,the chief error sources and influencing factors of ball-screw shaft travel variation in thread hard whirling process is analysed and confirmed.Based on the monitoring of support force from supporter,a prediction method of ball-screw shaft travel deviation in thread hard whirling process is proposed and verified.Based on the theory of linear elastic mechanics,the influence of several factors on travel deviation of ball-screw shaft machined by thread hard whirling are studied,such as workpiece revolution speed,cutting force,distance between follow rests,clamp length of follow rest,and constrained type of follow rests and supporter.At last,technical measures about the travel deviation control of hard whirling ball-screw shaft are discussed.