Modeling And Optimization Of Bone Milling Parameters And Vibration Analysis Of Medical Ball-end Milling Cutter

With the development of technology,surgery has gradually transitioned from manual milling to robot-assisted milling.However,there are few studies on the effect of milling parameters on the mechanical and thermal damage of bones during bone milling.In order to reduce the damage of bone cells and adjacent tissues during bone tissue resection and obtain good cutting surface quality,it is particularly important to use reasonable milling parameters in different bone tissue areas to minimize milling force and temperature and suppress flutter.In this paper,the means of combining theoretical analysis and experiment is used to study the problems related to bone milling.To explore the influence of milling parameters(rotational speed,feed rate,milling depth)on bone milling force and surface milling temperature when using medical ball-end milling tools for bone milling,the prediction model was established,and sensitivity analysis and multi-objective optimization were performed on the effective parameters to obtain the optimal milling parameters.At the same time,the vibration analysis of the bone milling process was carried out,and the influence of the milling parameters on the vibration was analyzed to seek measures to suppress the milling chatter.Theoretical analysis of the problem of bone milling was carried out.Based on the milling theory in the field of mechanical processing,the microstructure and mechanical properties of bone as an anisotropic material were explained.From the perspective of a single cutting micro-element,the cutting micro-element cutting model of the ball-end milling cutter was established,the cutting force formula of the ball-end milling cutter cutting micro-element was derived,and the relationship between the single cutting micro-element cutting force and the milling parameters was obtained.It provides theoretical support for subsequent research,and is compared with the milling force and temperature prediction results and experimental results.The heat flux density model and the temperature model of the milling area during ball milling were established,and the relationship between the maximum temperature of the bone milling surface and the milling parameters was obtained.Based on the central composite design method,the experimental plan of bone milling was designed.Based on Design-Expert,the response surface method is used to establish the prediction model of milling force and temperature on cutting parameters,and the relationship between the milling force and temperature response and the influencing factors(milling parameters)is intuitively reflected in the response surface diagram.The Sobol method is used to analyze the sensitivity of the milling force and temperature prediction mathematical model parameters,in order to clarify and quantitatively analyze.Based on the Derringer’s satisfaction function method,the multi-objective optimization of the milling force and milling temperature prediction model was carried out.By optimizing to find the best milling parameters,the milling force is minimized and the milling efficiency is high within the acceptable temperature range without bone tissue thermal damage,which lays the foundation for optimizing the milling parameters and reducing bone thermal damage in actual surgery.The mechanism of regenerative chatter during milling was briefly explained.The dynamic milling model of bone milling for medical ball-end milling cutters was established,the bone milling stability leaflet map was obtained by solving the stability domain.The effect of cutting parameters on the stability of bone milling was explored based on the leaflet diagram,and the chatter suppression measures during bone milling were discussed.Before machining,the milling parameters should be optimized,the rotational speed range should be appropriately increased,the feed rate and milling depth should be appropriately reduced to suppress chatter vibration in bone milling,and improve the stability and processing quality of bone milling.On the basis of theoretical analysis and prediction of bone milling force and milling temperature,the bone milling experiment table was designed and built.In different cutting modes,the acquisition experiment of the maximum milling force and the maximum milling temperature under different milling parameter combinations was completed.Through comparative analysis of theoretical analysis results,model prediction results and experimental results,it was found that the three trends were basically the same.When other conditions are constant,the milling force decreases with the increase of the rotational speed of the ball-end cutter,and increases with the increase of the feed rate and the milling depth,the milled surface temperature increases with the increase of the rotational speed and the milling depth,and decreases with the increase of the feed rate.Therefore,the accuracy of the theoretical model and the prediction model of milling force and temperature are verified.Using the optimization results of the milling force and temperature prediction model,the milling parameters were set to complete the pig femur milling experiment.The force and temperature of the milling process were measured and compared with the prediction model optimization results,which verified the correctness of the prediction model optimization methods and results.