Modeling and experimental validation on temperature diffusion mechanism in high-speed bone milling

Abstract

• High-speed bone milling heat is mainly caused by the friction effect between the bone chip and the cutter tooth. • Cutting edge temperature is determined by the equivalent static plane heat source. • The bone material temperature distribution is obtained according to the constant temperature moving heat source. • The thermal damage factors could be calculated based on the temperature diffusion mechanism model in bone milling. In orthopedic surgery, thermal damage of bone affects the accuracy of the prosthesis fixation and delays the postoperative recovery time. In order to avoid thermal damage in high-speed bone machining, it is necessary to establish an effective relationship among machining parameters, tool parameters, and temperature distribution of bone materials. Based on the characteristics of bone material and high-speed processing, this study proposes a novel temperature diffusion mechanism model (TDMM) in high-speed bone milling. According to the model, heat during high-speed bone milling is mainly generated by the friction effect between the bone chip and the cutter tooth. Then the cutting edge temperature of the milling cutter is determined by the equivalent static heat source, and cutting edge is regarded as a moving heat source with constant temperature. Under the action of the moving heat source, the bone material temperature distribution was determined. Moreover, the degree of thermal damage of bone materials under different machining and tool parameters was evaluated. Next, a high-speed bone milling experiment platform was established, in order to obtain accurate cutting edge temperature and bone material temperature. According to a large number of experimental measurements, the theoretical prediction temperature values of the cutting edge and bone materials were found to be within the reasonable error range of experimental measurements. The proposed model was proved to reasonably predict the temperature of the cutting edge and bone materials in high-speed bone milling. Experimental results indicate that the processing methods, tool diameter, cooling method, and cutting layer have a noteworthy impact on bone material distribution in bone milling. Spray cooling method can reduce the bone material temperature significantly. And the bone material temperature outside the cutting layer can be greatly lower than that in the cutting layer. This study also indicates that according to the TDMM, it is convenient for surgeons to select the appropriate machining parameters, and for engineers to optimize tool design.