| 摘要 |
PURPOSE:To enable precise and rapid detection of a tool blade face position, by a method wherein the coefficient of a change in a rotation speed of a tool spindle in the natural damping curve of inertia rotation is normally recognized, and a fluctuation in the coefficient of a change in a rotation speed occasioned by contact between a tool and a workpiece is mechanically caught. CONSTITUTION:The number of revolutions of a spindle motor 14 is detected by a tachometer 26, the detecting value is inputted to a CPU, and even after a motor 14 is stopped according to a command from the CPU at a point of time when the number of revolutions exceeds a maximum value, rotation of a spindle 12 is continued by virtue of inertia. By means of a signal from the CPU, the spindle 12 is lowered at a constant and low speed togetherwith an arm 16 through the working of a second drive source. During the lowering, the coefficient of a change in a rotation speed is normally detected by means of the CPU, it is caught by the CPU that the efficient of a change in a rotation speed is fluctuated in a manner to exceed a threshold due to contact between a grinding wheel 20 and a dress board 22, and from a value from a position detector at a point of time of the fluctuation, the Z-axis position of the grinding wheel 20 can be precisely and rapidly detected.
|
