Identification of thermal effects on the diameter deviation of inhomogeneous aluminum metal matrix composite workpieces when dry turning

The use of dry cutting is associated with considerable thermal loads on the machine tool, the tool and the workpiece because of the missing heat convection through the cutting fluid. These thermal loads cause thermal expansions of the components. The accuracy of machining is thus decreased. In recent years, particularly the thermal expansions of the workpiece and the tool attained significance due to the increased demands on the machining accuracy. Aluminum metal matrix composites (Al-MMCs) show a poor machinability due to the reinforcement of light metal alloys via hard and abrasive materials. Dry turning of such composites is therefore accompanied with high thermal workpiece and tool loads. In this paper, finite element models of the workpiece and the tool are used in order to calculate the temperature distribution and thus the thermally induced expansion of the workpiece and the tool when turning AL-MMC regarding the cutting condition used. The removal of material and the heat flow to the environment are considered. The required boundary conditions (e.g. the heat flow into the workpiece) for the simulations were determined using experimental results. A new evaluation method of experimental diameter measurement validates the numerically calculated diameter deviations and reveals a considerable effect of the thermal expansions of the workpiece and the tool on the accuracy of machining