Investigation of the effect of cutting parameters on forces in orthogonal cutting of cortical bone

In bone cutting operations, which are widely applied in orthopedic surgery, temperature related damage (necrosis), fracture of the cutting tool or cut bone due to cutting force depends on the intensity and direction of the micro forces on the cutting tool during the operation. The study of the effects of bone tissue properties on micro cutting forces is of great importance in the development of tools that can be used medically in such operational procedures. The determination of the relationship between cutting force and bone damage is carried out by physical tests in which bone cutting operations are performed outside of real operations. The aim here is to ensure that the surgically intervened bone heals quickly with minimal damage during operations. For this purpose, the forces occurring in cutting should be determined. In this study, a series of milling operations will be performed along the longitudinal axis of the cortical bone (parallel to the osteon), where orthopedic damage is most common. In this study, bovine cortical femoral bone was chosen because of its easy availability and limited health risks. Two finger mills with a diameter of 10 mm and different cutting edge angles will be used as cutting tools in the machining industry. An experimental study consisting of two stages will be carried out. The first stage experimental combinations were created using L18(21x33) Taguchi orthogonal arrays and 18 cutting experiments were conducted based on this arrangement. The input parameters were determined as number of cutting tool flute, cutting speed and depth of cut with two and three levels, and the output parameters were determined as cutting temperature and chip morphology. The second stage experimental combinations were created using L16(24) Taguchi orthogonal arrays and 16 cutting experiments were conducted based on this arrangement. The input parameters were determined as number of cutting tool flute, depth of cut, feed rate and cutting speed with two levels each, and the output parameters were determined as cutting force, cutting temperature and chip morphology. The microstructures of the cut chip surfaces have been analyzed using SEM and photomicrograph images. The effects of the experimental input parameters on the cutting force and temperature coefficients were determined in percentages by analysis of variance and the interactions and optimization of the machining parameters were created. According to the machining outputs obtained as a result of the analysis, the most ideal machining parameter levels were reached at 2 flute cutting tool, 0,1 mm depth of cut, 50 mm/min feed rate and 28 m/min cutting speed. The cutting force value obtained from the analysis results performed with these parameters was measured as 2,382 N and the temperature value was measured as 24,8 °C. According to the ANOVA results, it was determined that the most important parameters affecting the force in machining the bone in the osteon direction were the number of cutting tool edges, depth of cut, followed by cutting speed and feed rate, and their effects were 52,65%, 40,07%, 4,43%, 1,73%, respectively.