Research On Characterization Of Tool Wear Based On High And Low-Frequency Vibration Signal

In CNC machining,tool wear on-line monitoring is a very important issue.Many of the relevant feature quantities in the tool wear process will change,Including: cutting force,machine vibration,surface quality.In the past,the study of tool wear is mainly focused on the cutting force signal and the high frequency vibration signal of the tool,and some researchers have made good effect by analysis the characteristic value of the machine tool's low frequency vibration signal.During my researcher experiments,I found the tool high frequency and low frequency of machine tool wear sensitivity will change in a different wear stage.Therefore,the main content of this paper is characterize the tool wear from the tool highfrequency signal and low-frequency signal components of the machine tool.Firstly,the process damping is introduced to explain the high frequency vibration and low frequency vibration in the different stages of tool wear.Then describe the causes of process damping,and establish the relationship between the process damping and tool flank wear,the conclusion is that the process damping increases with the increase of tool wear.Secondly,the wear of the tool flank was measured by microscope,which was divided into VB=0mm,VB=0.4mm,VB=0.8mm three kinds of wear state,respectively,corresponding to the tool wear in the early,middle and late.Then the paper gives the measured data of the increase of positive pressure and friction caused by the increase of tool wear.The high and low frequency signals of the cutter in different wear stages were studied,combining the power spectrum of the cutting tool force signal and the tool vibration signal to study the change of the high frequency energy of the cutter,the power spectrum of the cutter head and the X table of the machine tool to study the change of the low frequency energy of the machine tool.The final conclusion is that high frequency vibration plays a dominant role in earlier stage of tool wear.In the middle stage of tool wear,the low frequency vibration of machine tool dominates due to the process damping increases and the high frequency vibration is suppressed,At the later stage of the tool wear,the vibration of the whole process system is greatly enhanced,and high-frequency vibration of the tool and low-frequency vibration of the machine components were enhanced at the same time.Finally,the tool wear is characterized by the change of the natural frequency in the low frequency band of the tool high frequency band and the machine tool part.Then comparing the the modal parameters of static percussion experiment and turning experiment in order to select the precise natural frequency.then analyze the change of the natural frequency amplitude of each group of cutting signals in the whole experiment process,and characterize the tool wear.The results show that the natural frequency amplitude of the high frequency of the tool and the low frequency signal of the machine tool component can well characterize the tool.