METHOD OF CALIBRATING A SURFACE SENSING DEVICE, CORRESPONDING CALIBRATING PROGRAM FOR A CONTROL COMPUTER AND CORRESPONDING CALIBRATION KIT

• US 20200132452A1
• Filed: 02/13/2018
• Published: 04/30/2020
• Est. Priority Date: 02/14/2017
• Status: Active Grant

• Current Assignee: Renishaw PLC
• Original Assignee: Renishaw PLC
• Inventors: REES, Martin Simon, BUTTER, Andrew Geoffrey, WALLACE, David Sven
• Granted Patent: US 11,650,050 B2
• Time in Patent Office: Days
• CPC Class Codes: G01B 11/007 feeler heads therefor
• CPC Class Codes: G01B 21/042 Calibration or calibration artifacts G01B3/30, G01B9/02072 take precedence
• CPC Class Codes: G01B 5/012 Contact-making feeler heads therefor
• CPC Class Codes: G01B 7/012 Contact-making feeler heads therefor

Abstract

A surface sensing device is mounted on an articulating probe head of a coordinate measuring machine. The device includes an elongate probe holder which is rotatable about an axis. An elongate sensing module includes a surface finish or surface roughness probe with a stylus tip. This is connected to the probe holder via an adjustable knuckle joint. To determine the geometry of the surface sensing device, including the tip normal and drag vector of the stylus tip, the orientations of the probe holder and the sensing module are determined by probing points which are spaced along their lengths, using a separate probe.

Claims

1. A method of calibrating a surface sensing device for use in position determining apparatus, the surface sensing device comprising one or more elongate members mounted to the position determining apparatus, and a surface sensing element mounted to the apparatus via the one or more elongate members, the method comprising probing at least one of the elongate members with a separate probe to determine its orientation.

2. A method according to claim 1, wherein one of the one or more elongate members is connected to a pivotable joint whereby it can be set at a desired angle.

3. A method according to claim 2, wherein there are first and second elongate members, and the pivotable joint connects the first and second elongate members whereby the second member can be set at a desired angle relative to the first member, the first elongate member being connected to the position determining apparatus, and the surface sensing element being carried by the second elongate member.

4. A method according to claim 3, wherein the probing comprises probing at least the second elongate member with the separate probe to determine its orientation.

5. A method according to claim 4, also comprising probing the first elongate member with a separate probe to determine its orientation, and then determining the angle of the second member relative to the first member.

6. A method according to claim 1, wherein the or each elongate member is probed at at least two positions spaced along its length.

7. A method according to claim 6, wherein the or each elongate member is probed at at least six positions.

8. A method according to claim 1, wherein the surface sensing device is one which senses unidirectionally

9. A method according to claim 1, wherein the surface sensing device is a surface finish or surface roughness probe.

10. A method according to claim 9, wherein the surface sensing element is a stylus with a tip, mounted to deflect in a normal direction when the stylus tip is dragged across a surface, and connected to a transducer to measure the deflection of the stylus thereby to determine surface finish or surface roughness.

11. A method according to claim 10, including determining the normal direction of the stylus tip and/or the direction in which the tip is dragged along the surface.

12. A method according to claim 11, wherein the normal direction of the stylus tip and/or the direction in which the tip is dragged along the surface is determined from the orientation(s) of the one or more elongate elements.

13. A method according to claim 10, including determining an offset which describes the location of the stylus tip relative to the position determining apparatus.

14. A method according to claim 13, wherein the offset is calculated from the orientation(s) and the length(s) of the one or more elongate members.

15. A method according to claim 13, wherein the offset is determined by probing the surface sensing device in the vicinity of the stylus tip with a separate probe.

16. A method according to claim 1, wherein the surface sensing device includes a rotary joint configured to rotate the elongate member connected to the position determining apparatus, generally about the longitudinal axis of the elongate member.

17. A method according to claim 16, including determining the orientation of the axis of rotation of the rotary joint.

18. A method according to claim 16, wherein the rotary joint has a motor for rotating the elongate member.

19. A method according to claim 1, wherein the surface sensing device is mounted to the position determining apparatus via an articulating head, configured to rotate the surface sensing device about two mutually orthogonal axes.

20. A method according to claim 19, wherein the articulating head includes motors for rotating the surface sensing device about the mutually orthogonal axes.

21. A program for a control computer of a position determining apparatus having a surface sensing device comprising one or more elongate members mounted to the position determining apparatus, and a surface sensing element mounted to the apparatus via the one or more elongate members, the program being configured to cause the position determining apparatus to perform a method according to claim 1.

22. A kit for use with a position determining apparatus, including a surface sensing device comprising one or more elongate members for mounting to the position determining apparatus, a surface sensing element for mounting to the apparatus via the one or more elongate members, and a program according to claim 21.