A Study on High Speed and High Accurate Machining by Using Linear Motor Applied Machine Tools

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Fundamental studies are conducted to utilize linear motor applied machine tools as a mother machine for agile manufacturing system. Main research results are follows.(1) Aiming for the machining of automotive parts like engine blocks and cylinder heads, high-speed machining tests are conducted. Machining materials are aluminum alloy(ADC12)and cast iron(FC25). In the face-milling tests of ADC12(tool : PCD)and FC25(tool : PCBN), surface roughness of machined surfaces are 4.6 μ mRy and 2.5 μmRy respectively. The step among the path is not critical, which means that Z-axis of this machine has enough rigidity in Z-axis. In the case of high speed end-milling of ADC12, surface roughness of 15μmRy is obtained on the machined surfaces. This means machine is not rigid enough in Y-axis, which is coming from the lack of servo stiffness.(2) Taking advantage of high-speed and high-acceleration feed drive, quick retraction motion at the bottom of the drilled hole is examined to see the effectiveness on tool wear. It is shown that this function extends the tool wear by 38% in the drilling of cast iron with the coated carbide tool.(3) In order to enhance the servo stiffness, a linear motor is installed in the high speed feed drive as a sub-actuator and conducts a damping control of vibration mode. By implementing damping control servo gain of velocity feedback is recovered 80% in the test bench, which realize high response and high servo stiffness.(4) The anti-vibration filters are designed to reduce the influence of vibrations on servo loop. It is shown that the simple filter, which suppresses the crucial vibration mode, can increase the feedback gain in the test bench.