Identification And Research Of Drill Axial Deviation Based On Sensor Signal

In drilling process, when drill point contacts the workpiece, the transverse vibration of machine tool spindle sometimes leads drill deviate from the center of spindle rotation, so that it causes the phenomenon of drill axial deviation. This phenomenon! would reduce the machining quality of hole on part. Seriously, it would even lead to part scrapped. How to identify drill axial deviation quickly and accurately is the key point to carry out the inhibition research of drill axial deviation. In this paper, a method based on the sensor signal for identification of drill axial deviation is proposed. And drill axial deviation mechanism analysis, acquisition and pretreatment of sensor signal, extraction, time and frequency domain analysis and pattern recognition of drill axial deviation characteristic signal and experimental verification have been studied.(1) The analysis of drill axial deviation mechanism. Based on the classical mechanics model of the beginning of drilling, force condition of drill is analyzed in detail. And performance characteristic of drill axial deviation is deduced. Then, a new idea of using the sensor signal to research the drill axial deviation is presented.(2) Acquisition and pretreatment of sensor signal. By building the drilling experiment platform, vibration signal, AE signal and spindle power signal are acquisited. And the original signal has been processed by spectral subtraction.(3) The extraction and analysis of drill axial deviation characteristic signal.!Firstly, the RMS analysis and amplitude change rate of the spindle power signal are calculated, and the signal of the beginning of drilling is extracted. Then, EMD decomposition method is used to extract drill axial deviation characteristic signal, and time domain analysis is carried out.!Finally, the AR model power spectrum estimation is performed on the drill axial deviation characteristic signal, and its characteristic in the frequency domain is analyzed.(4) Research and analysis of drill axial deviation based on wavelet packet decomposition and fractal box dimension. According to the characteristic of drill axial deviation characteristic signal in frequency domain, firstly, wavelet packet decomposition is used to divide drill axial deviation characteristic signal into several node signals, and the mutation signal is separated from them. Then, the fractal box dimension method is used to solve the dimension of each node’s signal. Finally, quantitative analysis of the change of the fractal dimension is carried out.(5) Experimental verification of drill axial deviation and its effect on the surface quality. Two kinds of experiments have been carried out. One is to judge whether the drill axial deviation occurs in drilling process by comparing the diameter of the front-end and the back-end of hole. The other is to measure the surface roughness of front-end of hole to classify the influence degree of drill axial deviation on hole surface quality, and then compare with the theoretical analysis results, in order to evaluate the effectiveness of the theoretical analysis results.Theoretical analysis and experimental results show that using the method proposed in this paper, not only can effectively identify the drill axial deviation, but also can accurately evaluate the influence degree on hole surface quality. This method would provide a new idea for inhibition research of drill axial deviation in the future.