AbstractsEngineering

The final shape of mechanical parts is mainly determined through turning, boring, drilling and milling operations. The prediction of the cutting forces, torque, and power of the machining process, and surface errors and vibration marks left on the parts is required to plan the machining operations and achieve shorter production cycle times while avoiding damage on the part, tool and machine. Past research has focused on developing dedicated mathematical models for each machining operation and tool type. However, the tool geometry and configuration of the machining set-up varies widely depending on the part geometry and application. This thesis presents a generalized mathematical model of machining operations carried out using geometrically defined cutting edges. The mechanics of cutting between the tool edge and the work material are modelled to predict the friction and normal forces on the rake face of a single cutting edge. The combined static and dynamic chip thickness is modelled as a function of tool geometry, the kinematics of machining operation and the relative regenerative vibrations between the tool and workpiece. The cutting forces are transformed to process coordinates by considering the orientation of cutting edge and the kinematics of the machining operation, and are applied on the structural dynamics of the machine tool and workpiece by distribution along the cutting tool–workpiece contact zone. The cutting forces, vibrations, chatter stability and surface errors are simultaneously predicted in a semi-discrete time domain. The geometry and force transformation models are unified in a parametric, mathematical model which covers all cutting operations. The application of the proposed model is demonstrated on turning, drilling and milling operations; multifunctional tools that combine drilling-boring and chamfering in one operation; and two parallel face-milling cutters machining a plate from both sides. The proposed mathematical models are experimentally validated by comparing the measured forces, surface errors, vibrations and chatter stability charts against simulations. The thesis shows the first unified, generalized mathematical modelling of metal cutting operations in the literature. The proposed model is expected to widen the application of science-based machining process simulation, planning and optimization methods in the virtual production of parts.