Automatic measurement/compensation apparatus for tool diameter

Claim 1

An automatic measurement/compensation apparatus for the tool diameter of a machine tool which machines a workpiece by rotating a tool mounted on a main spindle, comprising a first non-contact detector provided on a fitting table of the machine tool which detects the displacement in one direction from the center of rotation of the rotating tool, a memory which stores the initial value X 0 measured by said detector of a reference tool when it is mounted on the main spindle and rotated and the initial value x 0 measured by said detector of an object tool before working when it is mounted and rotated, a first subtractor which calculates the thermal displacement amount AX i of the difference between the measured value X i of the object tool after the predetermined number of workpieces by said detector and the initial value X 0 stored in said memory, a first register which stores the subtraction value AX i from said first subtractor, a second subtractor which calculates the variation in tool diameter of the difference between the measured value x i of the object tool after the predetermined number of workpieces detected by said detector and the initial value x 0 stored in said memory, a third subtractor which calculates the tool compensation value AT i of the difference between the tool variation Ax i from said second subtractor and the thermal displacement amount AX i stored in said first register, a second register which stores the tool compensation amount AT i from said third subtractor, an accumulator which accumulates the values sequentially stored in said second register, a comparator which compares the accumulated value AS i of said accumulator with a tool life criterion α and outputs an alarm signal if the relation AS i ≧α holds, and outputs a tool compensation signal, if the relation AS i <α holds, and a first adder which adds the tool compensation value AT i of said second register to the initial tool compensation value T 1 for generating a tool compensation signal CS, and for applying said CS signal to an NC system.