Calibration of a probe

• US 20040244464A1
• Filed: 04/20/2004
• Published: 12/09/2004
• Est. Priority Date: 11/01/2001
• Status: Active Grant

• Current Assignee: Renishaw PLC
• Original Assignee: Renishaw PLC
• Inventors: McFarland, Geoffrey, Wallace, David Sven, Hajdukiewicz, Peter
• Granted Patent: US 7,055,367 B2
• Time in Patent Office: Days
• US Class Current: 73/1.79
• CPC Class Codes: G01B 21/042 Calibration or calibration artifacts G01B3/30, G01B9/02072 take precedence

Abstract

A method of calibrating an analogue probe (10) having a stylus (12) with a workpiece-contacting tip (14) or a non-contact probe (26). A calibration artefact such as a calibration sphere (16) is mounted on a coordinate measuring machine (CMM) (18). The probe (10,26) is mounted on an arm (8) of the CMM and the probe is moved along a path whilst continually scanning the surface of the calibration artefact such that the probe is exercised throughout its working range. For an analogue probe (10) having a workpiece-contacting stylus (12), the path is such that the deflection of the stylus varies along the path For a non-contact probe (26) the path is such that there is variation of the radial distance between the path and the calibration artefact. The probe path may comprise a path parallel to a chord of the calibration sphere or a curved, e.g. a sinusoidal, path.

Claims

1. A method of calibrating a probe comprising the steps of:

mounting a calibration artefact on a first part of a coordinate positioning machine;

mounting the probe on a second part of the coordinate positioning machine, said second part being movable with respect to said first part;

moving the probe along one or more scan paths around the calibration artefact whilst continuously scanning the surface of the calibration artefact such that the probe is exercised through its working range;

and using measurement data from the probe and the coordinate positioning machine to determine the calibration coefficients of the probe.

2. A method of calibrating a probe according to claim 1 wherein the probe is an analogue probe having a stylus with a workpiece-contacting tip and wherein the path of the probe is such that the amount of deflection of the stylus varies along the path.

3. A method of calibrating a probe according to claim 2 wherein at least one scan path is scanned at two or more different stylus deflections.

4. A method of calibrating a probe according to claim 1 wherein the probe comprises a non-contact probe.

5. A method of calibrating a probe according to claim 4 wherein the measurement data for the probe is obtained for two or more different radial distances between the scan path and the calibration artefact.

6. A method of calibrating a probe according to claim 1 wherein the calibration artefact comprises a sphere and at least part of the path of the probe is parallel to a chord of the sphere

7. A method of calibrating a probe according to claim 1 wherein the path of the probe comprises a sequence of lines parallel to chords of the sphere.

8. A method of calibrating a probe according to claim 1, wherein the path of the probe comprises a sinusoidal path.

9. A method of calibrating a probe according to claim 1 wherein the direction of the path of the probe is reversed.

10. A computer program for operating the method of claim 1.