Modeling of oscillating bone sawing forces with instantaneous cutting speed and depth of cut

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Oscillating bone sawing is a crucial procedure in orthopedic surgery, but excess sawing forces are often detrimental to implant fixation and postoperative patient recovery. Therefore, understanding and controlling sawing forces are critical. However, the conventional bone cutting model is not applicable to the oscillating sawing process, as it requires variable speed cutting with a negative rake angle, which is affected by the difference in viscoelasticity of the bone at different speeds. In this study, an oscillating sawing force model was developed that considered variations in cutting speeds and depth of cut for each saw tooth. A speed-related cutting force model, including ploughing force in the tool edge and rake face, was developed, considering the effect of speeds on fracture toughness and normal stress based on orthogonal cutting experiments. Moreover, the model accounted for each saw tooth's instantaneous depth of cut by considering the depth of elastic recovery and interference effect of adjacent saw teeth, based on a kinematic model of the saw tooth tip. The impact force in the blind groove cut and the acceleration effect on cutting force were also considered in the model. The proposed model accurately predicts sawing forces, offers insights for reducing them through design parameter modifications, and has potential applications in medical training simulations, robotic-assisted surgery, and the optimization of saw blade shapes or movement to reduce sawing forces.