Method of finding a feature using a machine tool

Patent metadata

Field	Value
Publication number	US-9733060-B2
Application number	US-201314391822-A
Country	US
Kind code	B2
Filing date	Apr 16, 2013
Priority date	Apr 18, 2012
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

A method of finding a feature of an object using an analogue probe mounted on a machine tool. The method includes the analogue probe and/or object following a course of motion which causes the analogue probe's surface sensing region to traverse across the feature to be found a plurality of times whilst approaching the feature over successive traverses so as to ultimately arrive in a position sensing relationship with the feature so as to collect scanned measurement data about the feature along at least part of a traverse.

First claim

The invention claimed is:

1. A method of finding an object using an analogue probe mounted on a machine tool, the method comprising causing the analogue probe and/or object to follow a course of motion which is configured such that the analogue probe is initially sufficiently far away from the object such that the analogue probe is not in a position sensing relationship with anything and the course of motion is configured to cause the analogue probe's surface sensing region to traverse past the object to be found a plurality of times whilst approaching the object over successive traverses so as to ultimately arrive in a position sensing relationship with the object so as to collect scanned measurement data about the object along at least part of a traverse.

2. A method as claimed in claim 1 , comprising halting movement along the course of motion in response to it being determined that scanned surface measurement data in accordance with at least one criterion has been collected.

3. A method as claimed in claim 2 , comprising halting movement at some point after scanned surface measurement data in accordance with the at least one criterion has been collected.

4. A method as claimed in claim 3 , in which the surface sensing region continues along its traverse after the scanned surface measurement data in accordance with the predetermined criterion has been collected, until a subsequent predetermined condition has been met.

5. A method as claimed in claim 4 , in which the subsequent predetermined condition is that the course of motion has reached a predetermined point.

6. A method as claimed in claim 5 , in which the predetermined point is that point at which the surface sensing region reaches an end of the traverse in which the first predetermined criterion was met.

7. A method as claimed in claim 2 , in which the at least one criterion is a predetermined threshold indicative of the analogue probe obtaining a minimum level of data regarding the object.

8. A method as claimed in claim 2 , in which it is determined at predetermined intervals whether the analogue probe obtained scanned surface measurement data along the surface of the object.

9. A method as claimed in claim 8 , in which at the predetermined intervals, the analogue probe's output collected prior to the predetermined interval is analysed to determine whether the analogue probe obtained scanned object measurement data, prior to resumption of relative movement along the path.

10. A method as claimed in claim 1 , in which movement is halted immediately in response to it being determined that scanned surface measurement data in accordance with at least one second criterion has been collected.

11. A method as claimed in claim 10 , in which the at least one second criterion comprises a magnitude of data output by the analogue probe which is indicative of an undesirable positional relationship of the object and analogue probe.

12. A method as claimed in claim 1 , in which the difference between previous and subsequent traverses is sufficiently small such that if along the previous traverse no surface measurement data was obtained, the subsequent traverse will not cause the analogue probe to exceed its measurement range.

13. A method as claimed in claim 1 , in which it is determined whether the analogue probe obtained scanned measurement data based solely on the data from the analogue probe.

14. A method as claimed in claim 1 , comprising determining the location and/or orientation of the object based on the scanned measurement data obtained.

15. A method as claimed in claim 1 in which the analogue probe is a contact scanning probe comprising a deflectable stylus for contacting the object.

16. A method as claimed in claim 1 , in which the method comprises finding an edge of the object.

17. A non-transitory computer readable medium comprising instructions which when executed by a machine tool apparatus causes the machine tool apparatus to perform the method of claim 1 .

18. A method as claimed in claim 1 , wherein the analogue probe traverses past the object over a plurality of successive traverses before approaching the object.

19. A method of finding an object using an analogue probe mounted on a machine tool, the method comprising
moving the analogue probe to an initial position sufficiently far away from the object by an offset distance such that the analogue probe is not in a position sensing relationship with anything,
moving the analogue probe and/or object back and forth along a scanning path which is configured to move the feature of the object and the analogue probe past each other,
at predetermined intervals determine whether the analogue probe obtained scanned measurement data along the surface of the object that exceeds a predetermined threshold indicative of the analogue probe obtaining a minimum level of data regarding the object,
gradually reducing the offset distance of the scanning path until the obtained scanned measurement data exceeds the predetermined threshold, and
subsequently taking action based on the result of said determination.

20. A method as claimed in claim 19 , wherein the gradually reducing is a stepwise reduction of the offset distance between the back and forth movement along the scanning path.

21. A method as claimed in claim 19 , wherein the gradually reducing is a continuous reduction of the offset distance, resulting in a zigzag scanning path.

22. A machine tool apparatus comprising a machine tool, an analogue probe mounted on the machine tool, and a controller configured to control the relative movement of the analogue probe and an object to find said object, the controller being configured to control the analogue probe and/or object to follow a course of motion which causes the analogue probe's surface sensing region to, from a starting position initially sufficiently far away from the object such that the analogue probe is not in a position sensing relationship with anything, traverse past the object to be found a plurality of times whilst approaching the object over successive traverses so as to ultimately arrive in a position sensing relationship with the object so as to collect scanned measurement data about the object along at least part of a traverse.

23. A method of finding an object using an analogue probe mounted on a machine tool, the method comprising the steps of:
a scanning step comprising scanning to find the object using the analogue probe by causing the analogue probe and/or object to follow a course of motion along a scanning path, the scanning path configured such that the scanning path is offset in a first direction from the object so that initially the analogue probe is not in a position sensing relationship with anything;
an adjusting step comprising adjusting the scanning path in the first direction such that the offset is reduced by an incremental amount;
alternating between the scanning step and the adjusting step until a surface sensing region of the analogue probe is in a position sensing relationship with the object so as to collect scanned measurement data about the object along at least part of a scanning step.

24. A method as claimed in claim 23 , wherein the analogue probe traverses past the object over a plurality of successive traverses before approaching the object.

Assignees

• Renishaw Plc

Inventors

• Ould John
• Tett Kevin

Classifications

• G01B21/045 Primary

  Correction of measurements (G01B9/02055 takes precedence) · CPC title

• G01B7/012 Primary

  Contact-making feeler heads therefor · CPC title