Experimental analysis, mathematical modeling and Sobol sensitivity analysis of surface roughness in orthopedic milling process (polymethylmethacrylate)

One of the common treatments in orthopedic surgery is machining of knee joints to attach the artificial joint. In this surgery preparation of tibia and femur surfaces is necessary to obtain proper joint kinematics and ligament balancing. For this purpose milling is involved in surgery requiring accurate machining of bone surfaces and creation of accurate slots. In this paper, milling process was carried out on polymethylmethacrylate as workpiece and suitable substitute for bone and for the first time, it is focused on modeling and optimizing the effective parameters in milling namely cutting speed, feed rate, tool diameter and cutting depth for analyzing the surface roughness using the surface response methodology. The second-order regression equation governing the model is drived and the influence of the input parameters and their interaction on the surface roughness as the output parameter is carefully investigated. Also, sobol statistical sensitivity analysis is used to ascertain the effect of process input parameters quantitatively. The results show that in order to achieve the desirable surface quality, minimum of feed, minimum rotational speed, smaller tool diameter and low cutting depth should be considered. Results show that among all effective input parameters tool rotational speed, feed rate, tool diameter and ctting depth have the highest influence on process roughness respectively. The behavior of each output parameters with variation in each input parameter is further investigated.