Method of processing workpiece

Abstract

A method of grinding a workpiece is carried out by a grinding apparatus including a spindle for rotating a grinding wheel, a servomotor for moving the spindle, and a servo driver for sending signals to the servomotor. The method includes a depth-of-cut command issuing step of issuing a command representing a projected depth of cut to the servo driver and a grinding step of grinding the workpiece. In the grinding step, the servo driver finishes movement of the spindle when the spindle has moved by a target distance corresponding to the projected depth of cut.

What is claimed is: 
     
         1 . A method of processing a workpiece by grinding the workpiece on a grinding apparatus including
 a chuck table having a holding surface for holding the workpiece thereon, the chuck table being rotatable about an axis transverse to the holding surface,   a spindle for circumferentially rotating a disk-shaped grinding wheel mounted thereon and including grinding stones,   a grinding feed unit having a servomotor for relatively moving the chuck table and the spindle toward and away from each other,   a servo driver for sending signals to the servomotor of the grinding feed unit, and   a control unit for controlling the servo driver,   the method comprising:   a holding step of holding the workpiece on the holding surface of the chuck table;   a depth-of-cut command issuing step of calculating a projected depth of cut by subtracting a target thickness registered in advance in the control unit for the workpiece from a thickness of the workpiece and issuing a command representing the calculated projected depth of cut from the control unit to the servo driver of the grinding feed unit; and   a grinding step of relatively moving the chuck table and the spindle toward each other with the servomotor of the grinding feed unit while the chuck table and the grinding wheel are being rotated about respective axes thereof, thereby grinding the workpiece held on the chuck table with the grinding stones, wherein   in the grinding step, relative movement of the chuck table and the spindle is finished by the servo driver when the chuck table and the spindle have relatively moved by a target distance corresponding to the projected depth of cut.   
     
     
         2 . The method of processing a workpiece according to  claim 1 , wherein
 the grinding apparatus further includes a thickness measuring unit for measuring the thickness of the workpiece held on the holding surface of the chuck table,   the depth-of-cut command issuing step includes repeatedly measuring the thickness of the workpiece with the thickness measuring unit until the thickness of the workpiece reaches the target thickness, updating the projected depth of cut with a value calculated by subtracting the target thickness from the measured thickness of the workpiece, and repeatedly issuing a command representing the updated projected depth of cut from the control unit to the servo driver of the grinding feed unit, and   the grinding step includes updating the target distance on the basis of the updated projected depth of cut by the servo driver each time the servo driver is supplied with the command representing the updated projected depth of cut from the control unit until the chuck table and the spindle have relatively moved by the target distance.