Method and apparatus for measuring a part

• US 10,132,622 B2
• Filed: 02/03/2014
• Issued: 11/20/2018
• Est. Priority Date: 02/05/2013
• Status: Active Grant

• Current Assignee: Renishaw PLC
• Original Assignee: Renishaw PLC
• Inventors: Ould, John
• Primary Examiner(s): Henson, Mischita
• Application Number:
  US14/765,188
• Publication Number:
  US 20150377617A1
• Time in Patent Office: 1,751 Days
• CPC Class Codes: G01B 21/04 by measuring coordinates of points
• CPC Class Codes: G01B 5/10 of objects while moving
• CPC Class Codes: G01B 5/201 for measuring roundness
• CPC Class Codes: G01B 5/213 for measuring radius of curvature
• CPC Class Codes: G05B 19/401 characterised by control arrangements for measuring, e.g. calibration and initialisation, measuring workpiece for machining purposes G05B19/19 takes precedence
• CPC Class Codes: G05B 2219/37043 Touch probe, store position of touch point on surface

Abstract

A method and apparatus for measuring a part with a contact probe mounted on a coordinate positioning machine. The method includes measuring a plurality of points on the part when both the part and contact probe are moving continuously between different positions within the coordinate positioning machine. The probe moves, relative to the part, along a scan path such that substantially coincident points that are closely located together along a curve or surface being measured are measured at relatively far apart positions in the machine and at relatively far apart positions along the scan path.

Claims

1. A method of measuring a part with a contact probe mounted on a coordinate positioning machine, the method comprising measuring a plurality of points on the part when both the part and contact probe are moving continuously between different positions within the coordinate positioning machine, the probe moving to measure a plurality of sets of substantially coincident points on the part such that the substantially coincident points of each set are measured at spaced apart positions in the coordinate positioning machine and at spaced apart positions along a scan path, defined in a reference frame of the part,

wherein, for each set, between measuring the substantially coincident points of the set, the contact probe measures at least one point that is non-coincident therewith.

2. A method according to claim 1, wherein, the scan path comprises multiple scans of substantially the same scan path, the substantially coincident points measured on separate scans of the substantially the same scan path.

3. A method according to claim 1, wherein the scan path comprises a plurality of complete navigations around the part, the substantially coincident points measured on separate complete navigations of the part.

4. A method according to claim 3, wherein each complete navigation is around the same circumference of the part.

5. A method according to claim 3, wherein each complete navigation is offset from the other complete navigations.

6. A method according to claim 5, wherein the scan path is a helix or three-dimensional spiral around the part.

7. A method according to claim 1, wherein the continuous motion comprises movement of the probe and the part in non-orthogonal directions.

8. A method according to claim 1, wherein the contact probe is a multi-axis contact probe, in which measurements can be carried out through deflection of a stylus of the probe in any one of a plurality of measurement directions, the probe generating signals indicative of both magnitude and direction of the deflection, the method comprising moving the contact probe and the part such that, during the continuous motion, the contact probe carries out measurements through deflection of the stylus in at least two of the measurement directions.

9. A method according to claim 1, comprising fitting an analytical curve or surface to the plurality of points to obtain a representation of the part.

10. A method according to claim 1, comprising transforming a measured location for each point in a measurement coordinate system into a location in a part coordinate system in which relative positions of the points on the part are defined.

11. A method according to claim 10, wherein a position of the part in the coordinate positioning machine is determined at the time each point is measured, the measured location of the point within the coordinate positioning machine transformed into the location in the part coordinate system using the determined position of the part.

12. A method according to claim 1, comprising rotating the part within the coordinate positioning machine between the different positions.

13. A method according to claim 1, comprising a translation of the part within the coordinate positioning machine between the different positions.

14. A method according to claim 1, comprising determining a path for the contact probe to travel based upon an intended displacement of the part during measurement.

15. A method according to claim 14, wherein the path of the contact probe and/or displacement of the part is selected based upon set criteria.

16. A method according to claim 15, wherein the set criteria comprise a limited measurement range of the contact probe.

17. A method according to claim 15, comprising selecting a path of the contact probe and/or a displacement of the part such that points that are closely located to each other on the part are measured at two or more locations that are relatively far away in the coordinate positioning machine.

18. A method according to claim 1, wherein a distance between the substantially coincident points is smaller in the reference frame of the part than a distance between the spaced apart positions in which the substantially coincident points are measured in the coordinate positioning machine and along the scan path.

19. A method according to claim 9, comprising transforming a measured location of each point in a measurement coordinate system into a location in a part coordinate system in which relative positions of the points on the part are defined, wherein the curve or surface is fitted to the points once the points have been transformed into the part coordinate system.

20. A coordinate positioning machine comprising:

a first mount for mounting a contact probe for movement within the coordinate positioning machine; and

a second mount for mounting a part for movement within the coordinate positioning machine and a controller for controlling movement of the first and second mounts,

wherein the controller is arranged to control movement of the first and second mounts to measure with the contact probe a plurality of points on a surface of the part when both the part and contact probe are moving continuously between different positions within the coordinate positioning machine, the probe moving to measure a plurality of sets of substantially coincident points on the part such that the substantially coincident points of each set are measured at spaced apart positions in the machine and at spaced apart positions along a scan path, defined in a reference frame of the part, and

for each set, between measuring the substantially coincident points of the set, the contact probe measures at least one point that is non-coincident therewith.

21. A non-transitory data carrier having instructions thereon, wherein, when the instructions are executed by a processor, the processor is caused to control movement of first and second mounts of a coordinate positioning machine, the first mount for mounting a contact probe within the coordinate positioning machine and a second mount for mounting a part within the coordinate positioning machine,

wherein the processor moves the first and second mounts to measure with the contact probe a plurality of points on a surface of the part when both the part and contact probe are moving continuously between different positions within the coordinate positioning machine, the probe moving to measure a plurality of sets of substantially coincident points on the part such that the substantially coincident points of each set are measured at spaced apart positions in the machine and at spaced apart positions along a scan path, defined in a reference frame of the part, and

for each set, between measuring the substantially coincident points of the set, the contact probe measures at least one point that is non-coincident therewith.