Machine tool and method for correcting a position of a tip of the tool

Abstract

A machine tool includes a mounting table, a tool, a shade detector, and a tool controller. A workpiece is placed on the mounting table. The tool includes a tip. The shade detector is fixed on the mounting table, provides an optical path of a laser light, and detects a shade state of the laser light. The tool controller is connected to the mounting table via a supporting structure and controls an orientation and a position of the tool. A reference point associated with the tool is provided to the tool controller. The tool controller corrects a position of the tip based on a difference between a position obtained by calculation of the reference point in the case where the tip is matched with a measurement position P of a laswer light and a position of the reference point when the tip portion is acutally matched with a measurement position while keeping the orientation of a tool.

1 . A machine tool, comprising:
 a mounting table on which a workpiece is placed;   a tool configured to machine the workpiece placed on the mounting table, the tool including a tip;   a shade detector fixed on the mounting table and configured to provide an optical path of a laser light and detect a shade state of the laser light; and   a tool controller connected to the mounting table via a supporting structure and configured to control an orientation and a position of the tool,   wherein a reference point associated with the tool is provided to the tool controller, and   based on a first orientation, which is an orientation of the tool for machining, and on a length of the tool, the tool controller specifies a first tool position which is a position of the reference point in a state in which the tip is actually matched with a measurement position of the laser light, while keeping the first orientation.   
     
     
         2 . The machine tool according to  claim 1  wherein, when the tool is moved in one axial direction while the tool controller keeps the first orientation of the tool, the first tool position is determined based on a position of the reference point in a state in which the measurement position of the laser light is shaded in a first portion of the tool and a position of the reference point in a state in which the measurement position of the laser light is shaded in a second portion of the tool when the tool is moved in said axial direction. 
     
     
         3 . The machine tool according to  claim 2 , wherein
 the tool controller controls a position of the tool such that the reference point is positioned on a straight line connecting the measurement position of the laser light and a central point of the line defined by the above-described two positions, while keeping the first orientation of the tool,   the tool controller moves the tool such that the reference point is along said straight line, while keeping the first orientation of the tool, and   the first tool position is determined based on a position of the reference point in a state in which the measurement position is shaded by the tip when the tool is moved along the straight line.   
     
     
         4 . The machine tool according to  claim 1  wherein, when an orientation of the tool is changed from the first orientation to a second orientation,
 the tool controller, based on the second orientation and the length of the tool, specifies a second tool position which is a position of the reference point in a state in which the tip is actually matched with the measurement position of the laser light, while keeping the second orientation, and 
 the tool controller corrects a position of the tip in the second orientation of the tool based on a difference between the first tool position and the second tool position. 
 
     
     
         5 . The machine tool according to  claim 1  wherein, when the tool is exchanged for other tool,
 the tool controller, based on the first orientation and a length of the other tool, specifies a third tool position which is a position of the reference point in a state in which a tip of the other tool is actually matched with the measurement position of the laser light, while keeping the first orientation, and 
 the tool controller corrects a position of the tip in the first orientation of the other tool based on a difference between the first tool position and the third tool position. 
 
     
     
         6 . The machine tool according to  claim 1  wherein the tool controller can perform five-axis control of the tool. 
     
     
         7 . The machine tool according to  claim 1  wherein the tool is a ball end mill. 
     
     
         8 . A method for correcting a position of a tip of a machine tool, wherein the machine tool comprises:
 a mounting table on which a workpiece is placed;   a tool configured to machine the workpiece placed on the mounting table, the tool including a tip;   a shade detector fixed on the mounting table and configured to provide an optical path of a laser light and detect a shade state of the laser light; and   a tool controller connected to the mounting table via a supporting structure and configured to control an orientation and a position of the tool,   wherein a reference point associated with the tool is provided to the tool controller, and   the correction method comprises:   a matching process in which the tool controller actually matches the tip of the tool with a measurement position of the laser light, while keeping a first orientation which is an orientation of the tool for machining, the matching being based on the first orientation and a length of the tool; and   a first tool position specifying process in which a first tool position, which is a position of the reference point in a state in which the tip is actually matched with the measurement position of the laser light, is specified.   
     
     
         9 . The correction method according to  claim 8 , wherein the matching process comprises:
 a first moving process in which the tool controller moves the tool in one axial direction while keeping the first orientation; and   a specifying process in which the tool controller specifies, in the first moving process, a position of the reference point in a state in which the measurement position of the laser light is shaded in a first portion of the tool and a position of the reference point in a state in which the measurement position of the laser light is shaded in a second portion of the tool when the tool is moved in said axial direction.   
     
     
         10 . The correction method according to  claim 9 , wherein the specifying process comprises:
 a process configured so that the tool controller controls a position of the tool such that the reference point is positioned on a straight line connecting the measurement position of the laser light and a central point of the line defined by the above-described two positions, while keeping the first orientation of the tool and moving the tool such that the reference point is positioned along the straight line while keeping the first orientation of the tool; and   a process so that the tool controller specifies a position of the reference point in a state in which the measurement position is shaded by the tip when the tool is moved along the straight line.   
     
     
         11 . The correction method according to  claim 8 , further comprising:
 a second tool position specifying process in which, when an orientation of the tool for machining is changed from the first orientation to a second orientation, the tool controller, based on the second orientation and the length of the tool, specifies a second tool position which is a position of the reference point in a state in which the tip of the tool is actually matched with the measurement position of the laser light, while keeping the second orientation, and   a second tool position correcting process in which a position of the tip in the second orientation of the tool is corrected based on a difference between the first tool position and the second tool position.   
     
     
         12 . The correction method according to  claim 8 , further comprising:
 a third tool position specifying process in which, when the tool is exchanged for other tool, the tool controller, based on the first orientation and a length of the other tool, specifies a third tool position which is a position of the reference point in a state in which a tip of the other tool is actually matched with the measurement position of the laser light, while keeping the first orientation, and   a third tool position correcting process in which a position of the tip in the first orientation of the other tool is corrected by the tool controller based on a difference between the first tool position and the third tool position.