Machining of bone: an analysis of cutting force, surface integrity and chip morphology

Abstract

In orthopedic surgery, a damage bone is removed by method of machining in order to enable implant fixation. This requires high precision tools and techniques to prevent mistakes such as overcut and to avoid injuries to the surrounding tissues. This project involved the turning process where bovine bone samples were turned based on experimental conditions suggested by the response surface methodology (RSM) with a view of determining the optimum condition within the range investigated. At the same time an initial investigation on the cutting mechanism fundamentals for bone material was undertaken. The experiments were performed under dry cutting conditions. Cutting speed, depth of cut and feed rate were the main factors investigated while the main cutting force and surface roughness were the responses. Experiments were performed at cutting speeds ranging from 55 to 130 mm/min, with depths of cut in the range of 0.1–0.3mm, and feed rate from 0.04 to 0.09 mm/rev. The experimental plan was based on the central composite design (CCD). Chips after machining were observed and analyzed in order to see the influence of cutting conditions. The proposed mathematical models are adequately accurate to predict the performance indicators within the experimental range investigated. The most influencing factor on the cutting force is depth of cut, followed by feed rate, cutting speed and depth of cut interaction, depth of cut and feed interaction, and cutting speed respectively. Feed rate has the most effect on surface roughness while the cutting speed and feed rate2 factors presented secondary contribution on the surface roughness response. The partially continuous chips were observed at the cutting condition of 55 mm/min speed, 0.3mm depths of cut and 0.09 mm/rev feed rate indicating the possible occurrence of ductile mode machining on bone