| The overall dynamic characteristics of heavy gantry machining center determine its excellent machining performance.As a key component of gantry machine tools,the characteristics of the beam components will have a significant effect on the function of the machine tool.Machine tool,tool and workpiece constitute a dynamic milling process system in the milling of beam guideway groove.The interrelationship between the tool and the workpiece will produce the cutting force and cause the vibration.However,the vibration will change the interrelationship between tool and workpiece,and change cutting force again.The stability of the process system is destroyed by the cyclic action of cutting vibration and cutting force,which will reduce machining accuracy,deteriorate surface quality,shorten tool life and increase energy consumption.Therefore,it is important to study the vibration of milling guideway groove.This paper was supported by the key project of Heilongjiang Provincial Natural Science Foundation of China “Orderly multi-source flow evolution mechanism and key technology for energy-efficient milling of heavy machine base components(ZD2020E008)”.The vibration of the workpiece subsystem in the precision milling guideway groove process system were researched,including the establishment of the theoretical vibration model,the vibration testing,the prognosis of surface roughness and the method of vibration control.Firstly,the free vibration model of the workpiece system was established.Based on the FEM,the vibration model was transformed from the physical coordinate space to the modal coordinate space,so that the complex continuum vibration was decoupled into the superposition of multiple single freedom vibration,thus establishing the theoretical free vibration model of the guideway groove workpiece system.Subsequently,vibration simulation was launched to check the correctness of the theoretical model.The results showed that the natural frequencies of the guideway groove workpiece system calculated by the simulation and theory were close,and the model was more accurate.Secondly,the forced vibration model of the workpiece system was established.The centrifugal force excitation of spindle,the thrust force excitation of screw and the milling force excitation in the process system were considered.The forced vibration models of the guideway groove workpiece system subjected to harmonic periodic excitation and aperiodic excitation were established correspondingly.Subsequently,an experimental research was carried out to test the vibration of precision milling guideway groove,and the cutting amplitude and cutting force signals after WPT denoise were analyzed in the time and frequency domain to evaluate the vibration of the guideway groove workpiece system in actual machining and to establish the foundation for prediction of surface roughness.After the next,the surface roughness of guideway groove was predicted in cutting vibration.The influence of the guideway groove surface roughness on the beam performance of the heavy gantry machine tool was analyzed.The surface of the guideway groove after precision milling was sampled and observed with a WEDM and a white light interferometer respectively.The machine learning methods based on RBF-NNs and RBF-SVM were used to train and verify the prediction model respectively.The root mean square and kurtosis of cutting vibration characteristic parameters were used as inputs to predict Ra and Rz of the guideway groove.The results showed that RBF-SVM had superior precision and preferable prediction function.Finally,vibration control method for precision milling guideway groove was proposed.In order to reduce the root mean square and kurtosis of the cutting vibration,the cutting parameters in the target of vibration reduction were optimized based on the ABC algorithm,and testing were launched.The results found that the precision of the parameter optimization was superior.The target of vibration reduction in precision milling guideway groove has been achieved. |
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