In order to represent actual cutting process conditions, an in-process tribometer is examined to measure friction during orthogonal turning process at cutting speeds up to 300m/min. The tribometer consists of a spring preloaded tungsten carbide pin with spherical tip mounted behind the cutting edge and rubbing on the freshly generated workpiece surface. The pin preload is set according to feed force. A 3D-force measuring device in the fixation of the pin allows evaluating friction coefficient from tangential and normal forces. Experiments show strongly different results when contacting fresh and oxidized surfaces and decreasing friction coefficient with increasing cutting speed.
Analysis of the highest temperature in the machining processes, namely the flash temperature, helps to understand the physics of the process, to improve cutting tool geometry and to achieve high performance machining. In the present work, the interaction between cutting grain and workpiece material in grinding process is analyzed. Single diamonds are considered for machining, which operates in comparison to other measurements in the range of grinding speed. The highest temperature in the grain-material interaction and cutting forces are measured. In order to measure the flash temperature an innovative method to measure and analyze the temperature through the diamond grain in the cutting zone by two-color pyrometer are proposed. Furthermore, cutting forces are measured simultaneously. In order to measure the temperature in the cutting zone, an accurate connection between diamond and pyrometer fiber is required. Thus, the diamond tool holders are manufactured by electrical discharge machining (EDM)-milling in deionized water. A 0.5 mm diameter hole is drilled in each holder, to connect the diamond precisely to the pyrometer fiber. Machining processes are performed with 30 µm depth of cut, cutting length of 20 mm and cutting speed of 65 m/s on Ti6Al4V. The cutting tool is fixed and the shape of the rotating workpiece is optimized. The diamond holder with the specific shape is designed and manufactured. Quasi-static, dynamic, modal and harmonic response analyses are performed in order to reduce vibrations and chattering. The measured flash temperature is 1380 °C and cutting normal, tangential and axial forces are measured.
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