Patent ID: 7424776
Filing Date: 2008-09-16
Classification: B23B,B23D,Y10T

Abstract:
1. A method for machining a workpiece in which a plurality of machine tools each comprising a first chuck device for clamping one end part of the workpiece and a second chuck device for clamping the other end part of the workpiece are employed to carry out a machining operation on the workpiece, the machine tools being used in which the first chuck device and the second chuck device each comprise a chuck main body fixedly arranged in a tip end of a main spindle, a plurality of chuck jaws arranged to move freely along a radial direction of the chuck main body, a chuck jaw drive body, provided concentrically with a center axis of the main spindle and the chuck main body, that moves advancingly and retreatively along the center axis, and a pressing member supported rotatably and tiltably by the chuck jaw drive body through a spherical bearing disposed about the center axis and which is configured to clamp the workpiece by pressing a plurality of chuck jaw rods respectively linked with the plurality of chuck jaws using the pressing member in accordance with actuation of the chuck jaw drive body and by causing the plurality of chuck jaws to move in a radially inward direction, the workpiece being a crankshaft starting material for manufacturing a crankshaft having a predetermined number of journals and pins, a front shaft arranged at an end part of the workpiece on the first chuck device side, and a rear flange arranged at other end part of the workpiece on the second chuck device side, the method comprising the steps of: 1) in one of the machine tools, inserting centers of the first chuck device and the second chuck device into center holes of the workpiece, 2) performing rough-finish machining of outer circumferential surfaces of journals except for a first journal which is the closest to the first chuck device side, while clamping a starting material surface of the first journal of the workpiece by the first chuck device and clamping the starting material surface of the rear flange by the second chuck device, 3) performing milling machining of an outer circumferential surface of the first journal, while clamping the center of the first chuck device by a portion of the first chuck device, and clamping the starting material of the rear flange by the second chuck device, 4) in another of the machine tools, inserting the centers of the first and second chuck device into the center holes of the workpiece and performing grind machining of the outer circumferential surface of the rear flange, while clamping the staffing material of the front shaft by the first chuck device, and clampin the center of the second chuck device by a portion of the second chuck device, 5) performing grind machining of the outer circumferential surfaces of the front shaft and the first journal, while clamping the center of the first chuck device by a portion of the first chuck device, and clamping the grind-machined rear flange by the second chuck device, 6) performing semi-finish machining of the outer circumferential surface of the journals except for the first journal, while clamping the grind machined front shaft by the first chuck device, and clamping the grind machined rear flange by the second chuck device, and 7) in a further one of the machine tools, inserting the centers of the first and second chuck device into the center holes of the workpiece and performing semi-finish machining of an outer circumferential surface of the pins, while clamping the grind machined front shaft or the grind machined first journal by the first chuck device, and clamping the semi-finish machined rear flange by the second chuck device.