Research On Monitoring For Machine Deformation And Chatter Technology In Milling Process

The processing surface quality of the whole engine blades and the aviation structure play a key role in the mechanical properties in aerospace industry,whose surface quality could affect the engine performance,thrust weight ratio of the dynamic balance performance and reliability seriously.However it could cause deformation and chatter easily in the finishing stage,resulting in the production of processing errors which are difficult to control and affecting the surface quality and machining accuracy of the workpiece.So it is very important to establish the monitoring algorithm for the deformation and chatter during the cutting process.A method for monitoring the deformation of thin wall parts is proposed based on the least square method and lifting wavelet transform.First,the finite element model is established to calculate the deformation of the workpiece under the action of the unit force,after which the overall displacement matrix could be fitted using the least square method.The dynamic cutting force signal collected during processing is promoted by wavelet transform then,and the deformation of the workpiece could be monitored when apply the related component to the overall displacement matrix.The accuracy of the model is verified through some related cutting experiment.Based on band pass filtering and envelope demodulation technique,an early identification model for cutting chatter in fixed parameters is established.The dynamic cutting force in the initial stage of the process is decomposed into different frequency bands through the band-pass filter first.Then the envelope demodulation is carried out on the signals of different frequency bands,and the early chatter identification can realize by the spectral peaks on envelope spectrum.In order to verify the effectiveness of the proposed method,10 sets of milling experiments which consider the axial cutting depth and the spindle speed are designed.The error is less than 2Hz when comparing the chatter frequency identified with which calculated by observing the surface of workpiece,the effectiveness of the algorithm is verified.Considering the time variation of flutter frequency in variable parameter processing,the monitoring model of cutting chatter is established based on wavelet packet transform and approximate entropy feature.The dynamic cutting forces in different working conditions are transformed by wavelet packet transform first,and the bands with rich chatter information are selected to reconstruct.Then the approximate entropy characteristic curve with time could be plotted,and the chatter could be monitored by the change of the amplitude on the curve in the machining process.The monitoring algorithm is verified by some multi parameter varying parameter cutting experiments.The experimental results show that the approximate entropy can be used to characterize the stability of the system and have good robustness.