Prediction Of Surface Roughness In Turning Using Indirect Measurement And Wavelet Packet Analysis

Surface roughness is one of the most important indexes to evaluate the quality of the products.It has great influence on the wear resistance,corrosion resistance,fatigue strength and coordination properties of the parts.There are many factors that affect the surface roughness,including cutting parameters,tool geometry parameters,cutting tool material and workpiece material.And the tool vibration is the main factor affecting the surface quality of the workpiece.How to predict the surface roughness of the workpiece based on the existing information has always been one of the research hotspots.By predicting the surface roughness,the machining parameters can be adjusted in time to get better surface quality.The surface of the workpiece from macroscopic to microscopic is mainly divided into three characteristics: roughness,waviness and geometry.The main influence on the surface roughness is the high frequency vibration between the tool and the workpiece,and the vibration of the cutting tool in the depth direction of the cutting tool has a greater influence on the surface roughness than the other two directions.In this paper,the experimental platform is built,and the vibration acceleration sensors are arranged on the tool and the cutter head.The transfer function of the cutting point to the measuring point of the cutter head is measured,and the vibration acceleration signal of the tool tip is calculated indirectly by using the vibration signal of the measuring point.Using Matlab programming,the acceleration signal is smoothed,and denoised through wavelet packet.The post-pretreatment vibration acceleration signal is Fourier-transformed,and the displacement signal is obtained in the frequency domain,and then the inverse Fourier transform is carried out to obtain the displacement signal in the time domain.The vibration displacement signal is decomposed by wavelet packet,and each node is reconstructed,and then the energy ratio of different frequency bands can be calculated.The corresponding frequency band is transformed by FFT,and the amplitude and phase of the corresponding frequency signal are obtained.Finally,the displacement equation of the vibration signal is obtained,and the equation is composed of the cosine equation corresponding to several frequencies.In this paper,the formation mechanism of surface topography is analyzed.The motion equation of the cutting process is established,and the simulation model of the three-dimensional surface topography is obtained.The surface roughness can be obtained by 3D surface topography.The surface roughness of the workpiece is compared with the measured surface roughness,which verifies the accuracy of the analysis of the vibration displacement signal and the reliability of the indirect measurement method.