MACHINE TOOL HAVING FUNCTION OF CORRECTING MOUNTING ERROR THROUGH CONTACT DETECTION

• US 20090033271A1
• Filed: 07/18/2008
• Published: 02/05/2009
• Est. Priority Date: 07/31/2007
• Status: Active Grant

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: EBIHARA, Kenzo, HON, Yonpyo, KAWAI, Tomohiko
• Granted Patent: US 7,852,031 B2
• Time in Patent Office: Days
• US Class Current: 318/640
• CPC Class Codes: G05B 19/402 characterised by control arrangements for positioning, e.g. centring a tool relative to a hole in the workpiece, additional detection means to correct position G05B19/19 takes precedence
• CPC Class Codes: G05B 19/4083 Adapting programme, configuration
• CPC Class Codes: G05B 2219/36503 Adapt program to real coordinates, software orientation
• CPC Class Codes: G05B 2219/37405 Contact detection between workpiece and tool, probe, feeler
• CPC Class Codes: G05B 2219/37593 Measure correct setting of workpiece
• CPC Class Codes: G05B 2219/50046 Control of level, horizontal, inclination of workholder, slide

Abstract

A machine tool capable of automatically correcting an orientation of a workpiece or machining attachment based on detection results from position detectors that the machine tool inherently has. The machine tool comprises: position detectors; position deviation determining means; contact detection means that detects a contact between a probe and a surface of the workpiece or the machining attachment based on a position deviation; movable axis stopping means; coordinate value detection means; inclination determining means; and correction means. The inclination determining means moves linear axes to perform detection of contacts between the probe and the surface of the workpiece or the machining attachment at least two different points, and determines an inclination of the workpiece or the machining attachment using the obtained coordinate values. The correction means corrects a mounting error of the workpiece or the machining attachment, or corrects the machining program based on the determined inclination.

Claims

1. A machine tool controlled by a numerical controller and having movable axes respectively supported by fluid bearings for moving a workpiece relative to a tool held by a machining attachment according to a machining program, comprising:

position detectors for respectively detecting positions of the movable axes;

position deviation determining means that determines a position deviation between a position command for each of the movable axes and a position of each of the movable axes detected by said position detectors;

contact detection means that detects a contact between a probe and a surface of the workpiece or the machining attachment when the position deviation detected by said position deviation determining means exceeds a preset value;

movable axis stopping means that stops the movable axes at an instant when the contact is detected by said contact detection means;

coordinate value detection means that obtains coordinate values at the instant when the contact is detected by said contact detection means;

inclination determining means that moves linear axes of the movable axes so that the workpiece or the machining attachment is moved relative to the probe to perform detection of contacts between the probe and the surface of the workpiece or the machining attachment at least two different points on the surface by said contact detection means, and determines an inclination of the workpiece or the machining attachment based on a distance of motion of one of the linear axes and the coordinate values obtained by said coordinate value detection means; and

correction means that corrects a mounting error of the workpiece or the machining attachment, or corrects the machining program based on the determined inclination of the workpiece or the machining attachment.

2. A machine tool according to claim 1, wherein the movable axes comprise linear axes and rotary axes, and the position detector for detecting the position of the linear axis comprises a linear scale having a resolution of 10 nm or less.

3. A machine tool according to claim 1, wherein the position detector for detecting the position of the rotary axis comprises an encoder with a resolution of not greater than one ten-thousandth degree or less, and the rotary axis is directly coupled to a motor to be driven directly thereby.

4. A machine tool according to claim 1, wherein the surface of the workpiece is a side surface including at least one flat face to be parallel or perpendicular to a direction of machining of the workpiece.

5. A machine tool according to claim 1, wherein the machining attachment comprises a rotary machining attachment, and the surface of the machining attachment is a reference surface perpendicular to a rotary axis of a rotary tool of the rotary machining attachment.

6. A machine tool according to claim 1, wherein the machining attachment holds a cutting/scribing tool, and a side face of a shank of the cutting/scribing tool is used as the surface of the machining attachment.

7. A machine tool according to claim 1, wherein the probe is an elongate member made of metal to have a conical shape with a spherical end, and is attached to a distal end of an arm of which orientation is changeable and provided on a magnet holder.

8. A machine tool according to claim 1, wherein the workpiece and the machining attachment are mounted on different rotary tables driven by respective rotary axes of the movable axes, the probe is fixedly arranged on the rotary table on which the machining attachment is mounted when an mounting error of the workpiece is to be corrected, and the probe is fixedly arranged on the rotary table on which the workpiece is mounted when an mounting error of the machining attachment is to be corrected.

9. A machine tool according to claim 8, wherein said correction means automatically corrects the mounting error of the workpiece or the machining attachment by rotating the rotary axis on which the workpiece or the machining attachment is mounted in an opposite direction by an angle of the determined inclination.

10. A machine tool according to claim 1, wherein said correction means automatically corrects machining coordinate values of the machining program in accordance with the determined inclination.