Research On Cutting Edge Characterization And Evaluation Of Hard Whirling Tool For Large Ball Screw Manufacturing

Large ball screws are the key component of ultra-large manufacturing equipment and heavy-duty machine tools.The preparation of high-quality large ball screws is one of the key issues related to the independent research and development of high-end equipment.However,the manufacturing of large ball screws requires high machining accuracy,need more man-hours,and difficult to machine.It is particularly urgent to develop a high-efficiency and precise manufacturing method for large ball screws.As a high-speed hard dry cutting technology,hard whirling has the advantages of light and thin chips,low cutting force,high material removal rate and quick cutting heat dissipate rate.It has become the main processing method for large ball screws.However,hard whirling has the characteristics of time varying and interrupted cutting,and the cutting edge is easy to produce local early damage,and the tool life is short,which is one of the bottleneck problems that restrict the quality and efficiency of large ball screws.Starting from the uniform evaluation standard of cutting edge,the precision measurement and two-scale characterization method of hard whirling cutting edge are studied in this paper.The hard whirling process model is established,and the influence of preparation parameters on the machining quality and tool wear are analyzed.The failure mechanism and prolong life method of tool are also been discussed.The main works are presented as follows:1.Precision measurement of tool edge.The measurement characteristics of laser scanning confocal microscopy are analyzed,and the precision and uncertainty of the LSCM method are studied.Research shows that LSCM is efficient to obtain rich information of cutting edge,has high measurement precision,the uncertainty of criterion is superior to 0.08 ?m.It can be used as an efficient and precise method for non-contact type measurement of hard whirling cutting edge.2.Reconfiguration technology of cutting edge surface for hard whirling.According to the profile characteristics of the hard whirling tool for ball screw,the sparse sampling and processing flow of the cutting edge are set up.The identification of demarcation points based on curvature difference and data flattening processing method are studied,and provides the foundation for edge arc fitting and high precision reconstruction of cutting edge surface.The fractal interpolation reconstruction method for cutting edge surface is studied,which facilitates the accurate modeling and characterization of the cutting edge.The line scanning method and fractal interpolation based on the LSCM can guarantee the accuracy.The required time is about 3% of the surface scanning method and the efficiency is improved significantly.3.Cutting edge characterization method.The two-scale and multi-indexes characterization method which contains of cutting edge radius,fractal dimension and the shape factor are studied.It provides a uniform standard for the performance evaluation of hard whirling tool.4.Modeling of hard whirling process.The basic principle and movement characteristics of hard whirling are analyzed.Based on the principle of instantaneous cutting volume equivalent,a simplified model of hard whirling is established.The validity of the model is verified from chip morphology and cutting force.The influence of cutting edge parameters on cutting temperature and cutting force are studied by using the equivalent model.The results show that,under certain machining parameters,there is an optimized cutting edge radius,and the simulation results of cutting force with micro characteristics are more accurate.Compared with the experimental value,the error is 3.95%.5.Experimental research on hard whirling process.The influence of cutting parameters on cutting force and cutting temperature are studied by experimental method.The results show that the combination of small feed and high cutting speed can reduce cutting force and cutting temperature.Under the premise of ensuring the strength and avoiding the damage of the cutting edge,cutting force and cutting temperature can be reduced by selecting the smaller edge radius and chamfering parameters.The raceway surface machined by hard whirling is in residual compressive stress state.Considered the surface quality and efficiency,as far as possible to choose middle or low range of feed rate and high cutting speed.When the small edge radius is used,it is helpful to reduce roughness of the raceway surface.The roughness of machined surface increases when the edge radius is increased.6.The wear mechanism of hard whirling tool for large ball screw.The wear pattern,wear mechanism and tool life of hard whirling tool are studied by experimental methods,and the influence of cutting edge parameters on tool life is analyzed.The results show that increasing the edge radius within a certain range can increase the edge strength,and the probability of early damage of the tool is decreased by about 60%.As a matter of priority,a relatively large cutting edge radius should be adopted and the tool life can be prolonged by means of timely grinding,so as to ensure the quality of screw.The influence of radius,shape coefficient and fractal dimension of cutting edge surface on the wear of flank are studied by simulation method,and the empirical model is obtained.7.Optimization technology for cutting edge of hard whirling tool.The load and damage characteristics of hard whirling tool are studied,and a non-uniform cutting edge preparation method is proposed.Verified by failure patterns,non-uniform cutting edge preparation has outstanding advantages to enhance the overall damage resistance of tool.It provides the ideas for life extension design of cutting edge for large ball screw.