Research On Tool Wear Condition Monitoring Technology In NC Side Milling

In the process of NC side milling,tool wear will inevitably occur.If the tool fails to be replaced in time after achieving the blunt standard,it will not only increase the surface roughness of the workpiece,but also reduce the dimensional accuracy,or even lead to machine tool failure and abnormal milling.How to monitor the tool condition for uniform and non-uniform flank wear in NC side milling involves the improvement of tool condition monitoring accuracy,tool condition monitoring for non-uniform flank wear based on parametric modeling of milling force,tool condition monitoring for uniform flank wear and many other aspects.Based on the analysis and summary of previous research work,the tool condition monitoring technology for uniform and non-uniform flank wear based on the experimental data of titanium alloy side milling is presented.The main research work and achievements are as follows.(1)Research on synchronization method between teaching threshold and monitoring signal and cutting power extraction methodAiming at the problem that the cumulative synchronization error between the teaching threshold and the monitoring signal increases with time,a synchronization method between teaching threshold and monitoring signal is proposed.Aiming at the different effects of different un-load power and additional load loss characteristics of different machine tools on the collected input power signal,a cutting power extraction method is proposed.The two methods provide accurate input data for subsequent tool condition monitoring model.(2)Research on tool condition monitoring method for non-uniform flank wear based on parametric modeling of milling forceFirst,the parametric modeling method of the cutting edge are studied for the typical toroid-shaped end milling tool with multi-structure features of tooth offset center and introversion of bottom edge.Then,based on the parametric modeling of the cutting edge and with the help of oblique cutting theory and discretization modeling,a milling force parametric modeling model for the toroid-shaped end milling tool with multi-structure features of bottom edge is constructed considering tool non-uniform flank wear.Next,based on the comparative analysis of the theoretical and practical milling force among the new tool,the tool with uniform and non-uniform flank wear,a reasonable method for setting monitoring indexes is proposed,which provides reference data and theoretical guidance for tool non-uniform flank wear monitoring based on the parametric modeling model of milling force.(3)Research on tool condition monitoring method based on multi-stage dynamic coefficient evaluation methodBased on the teaching data of the normal milling,the influence of different tool wear stages on the characteristic value of the net cutting power signal in different power ranges is quantitatively analyzed.The multi-stage dynamic coefficients between net cutting power deviation and corresponding tool wear is solved.And according to the the calculated net cutting power deviation values of the standard signal section and the corresponding multi-stage dynamic coefficients,the tool condition monitoring for uniform flank wear under the condition of teaching is realized.(4)Research on tool condition monitoring method based on wear evaluation indexBased on the comparative test data of milling tools in different wear states,the eigenvalues are evaluated and the weight coefficients are calculated through the correlation coefficient and stability analysis between power signal eigenvalues and tool wear quantities.According to the difference and weight of tool characteristic values in different wear states,the evaluation index of tool wear is put forward,and the mapping model of tool wear evaluation index and tool wear quantity is constructed by Newton interpolation method.At the same time,the tool condition monitoring for uniform flank wear without teaching is realized by combining the eigenvalue obtained by support vector machine regression and the prediction value of wear evaluation index under the condition to be monitored.Through the above research,a whole set of tool condition monitoring scheme for uniform and non-uniform flank wear in NC side milling has been formed,which includes the synchronization method between teaching threshold and monitoring signal,cutting power extraction method,tool condition monitoring for non-uniform flank wear based on parametric modeling of milling force,tool condition monitoring for uniform flank wear.The scheme and the key technologies are proved correct and feasible by milling experiments.