Effects of Rotational Speed, Feed Rate and Tool Type on Temperatures and Cutting Forces When Drilling Bovine Cortical Bone

Abstract Surgical procedures that affect the human body's bone structure, often entail cutting, drilling or screwing operations of bone. The post-operative success of these procedures is largely dependent on the degree of damage introduced by the process. In this article, the influence of the rotational velocity, feed per tooth and two drill bit type on workpiece temperatures and cutting forces when drilling bovine cortical bone has been studied. The purpose is to find the optimum cutting conditions that will generate the lower temperatures and cutting forces. The measurement of temperatures has been carried out with an infrared thermography camera, and a piezoelectric dynamometer has been employed to obtain forces. A model has been developed from which heat flow into the drilled bone can be estimated from specific cutting force and the fraction of total heat generated that flows into the bone. This fraction has been shown to depend on the Peclet number for the process, proportional to the drill rotation speed, the feed per cutting edge and the diameter of the drill. By means of the model, some contradictions in the literature as to the effect on bone heating of increasing rotation speeds and feeds per cutting edge have been resolved. Keywords: bonecutting forcesdrillinginfrared thermographytemperaturesthermal necrosis ACKNOWLEDGMENTS The authors thank the Basque Government for the financial support extended to the projects Cutbone (S-PE09MU09) and Inprorret (IE12-342), and the grant for education and training of research staff of the author (BFI09.358). The authors gratefully acknowledge Professor Childs (Leeds University) for his comments and advice. Notes The main differences between tools are highlighted in bold.