Development of High-accurate and High-efficient Centerless Grinding Technology for Micro Cylindrical parts

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To develop a high-accurate and high-efficient machining technology for micro cylindrical parts, a new centerless grinding method without using the regulating wheel has been proposed. In this method, instead of the regulating wheel an ultrasonic vibrating shoe, the end of which is in elliptic motion at a high frequency, is employed to support the workpiece together with the blade. And the rotational speed of workpiece is controlled with the elliptic motion on the end of shoe. In addition, the in feed motion of shoe is given by a fine feeding unit. This work can be summarized as follows.(1) An ultrasonic shoe and a fine feeding unit composed of a ball screw, a stepping motor, a linear guide and a shoe holder have been designed and produced. Then an experimental apparatus has been constructed by installing the ultrasonic shoe and the fine feeding unit on an existing centerless grinder.(2) The performance in the elliptic motion of shoe has been investigated with a laser vibrometer when the AC voltage is applied for various voltages and frequencies.(3) Tests of rotationally driving the workpieces with sizes of 5mm in diameter have been conducted on the constructed apparatus. It is confirmed that the workpiece rotational speed can be controlled with the elliptic motion of the end of shoe.(4) The workpiece rotational speed depends on the bending vibration velocity of shoe, increasing with lager voltage and as the frequency become closer to the resonance points of shoe.(5) Grinding tests of pin-shaped workpieces with sizes of 1mm to 5mm in diameter have been carried out. As the results, the diameter of the smallest pin ground is 500μm, and the roundness improved from 20μm to 1.5μm.