Method and apparatus for calibrating a scanning probe

Patent metadata

Field	Value
Publication number	US-2019025793-A1
Application number	US-201716070998-A
Country	US
Kind code	A1
Filing date	Feb 22, 2017
Priority date	Feb 29, 2016
Publication date	Jan 24, 2019
Grant date	—

Abstract

A method for setting a null position of a scanning probe mounted to the rotatable spindle of a machine tool. This method may be performed as part of a probe qualification process. The method includes setting the null position using probe measurement data collected by the scanning probe when mounted to the spindle. In one embodiment, a stylus tip of the scanning probe may be located in a conical recess whilst the probe measurement data is collected. The set null position is arranged to be away from the rest position of the scanning probe and to substantially coincide with the axis of rotation of the spindle. The need to measure and use a probe offset value in subsequent measurement cycles can thus be avoided.

First claim

1 . A method for setting a null position of a scanning probe mounted to a rotatable spindle of a machine tool, the method comprising the step of setting the null position using probe measurement data collected by the scanning probe when mounted to the spindle, wherein the set null position is arranged to be away from the rest position of the scanning probe and to substantially coincide with the axis of rotation of the spindle.

2 . A method according to claim 1 , wherein the scanning probe comprises a probe body and an elongate stylus that extends from the probe body, the stylus comprising a workpiece contacting tip.

3 . A method according to claim 2 , wherein the scanning probe comprises one or more transducers within the probe body that measure deflection of the stylus and output probe measurement data describing deflection of the stylus.

4 . A method according to claim 2 , wherein the scanning probe is a suspended scanning probe, the stylus being attached to the probe body via a suspension mechanism that comprises a plurality of counteracting spring elements that suspend the stylus in a floating rest position in the absence of an externally applied force and which allow movement of the stylus away from the floating rest position when an external force is applied to the stylus.

5 . A method according to claim 2 , wherein the step of setting the null measurement position comprises collecting probe measurement data whilst the stylus tip is in contact with an artefact that constrains translation of the tip but allows rotation of the tip.

6 . A method according to claim 5 , wherein the artefact comprises a conical recess, three balls or a corner cube.

7 . A method according to claim 5 , wherein the spindle is rotated whilst translation of the stylus tip is constrained by the calibration feature and probe measurement data is collected by the scanning probe that describes deflection of the stylus at a plurality of different spindle rotational positions.

8 . A method according to claim 7 , wherein the probe measurement data is analysed to establish a positional difference between the spindle axis of rotation and a preliminary null position used by the scanning probe when collecting the probe measurement data, the null position being set by applying the established positional difference to the preliminary null position.

9 . A method according to claim 1 , comprising the step of locating an artefact on the bed of the machine tool such that it lies on the axis of rotation of the spindle, using the scanning probe to measure the positon of the artefact and using the measured position of the artefact to set the null position of the scanning probe.

10 . A method according to claim 1 , comprising an initial step of mechanically adjusting the position of the scanning probe relative the spindle to approximately align the rest position of the scanning probe to the axis of rotation of the spindle.

11 . A method according to claim 10 , when the mechanical adjustment comprises using a dial test indicator to measure alignment of the scanning probe.

12 . A method according to claim 1 , wherein the scanning probe outputs all probe measurement data relative to a preliminary null position prior to the null position being set.

13 . A method according to claim 1 , comprising the step of generating a trigger signal when the measurement data collected by the scanning probe exceeds a threshold, wherein the threshold is based on deviation from the set null position.

14 . Apparatus comprising a scanning probe mounted to the rotatable spindle of a machine tool, the null position of the scanning probe being arranged to coincide with the axis of rotation of the spindle.

15 . An apparatus according to claim 14 , wherein the scanning probe includes a memory for storing null position information.

16 . (canceled)

Assignees

• Renishaw Plc

Inventors

• Ould John Charles

Classifications

• G05B2219/37008

  Calibration of measuring system, probe, sensor · CPC title

• G05B2219/37069

  Calibrate probe, imitated tool, repeated measurements for different orientations · CPC title

• G05B19/401 Primary

  characterised by control arrangements for measuring, e.g. calibration and initialisation, measuring workpiece for machining purposes (G05B19/19 takes precedence) · CPC title

• G01B21/042 Primary

  Calibration or calibration artifacts (G01B3/30, G01B9/02072 take precedence) · CPC title

• B23Q17/22

  for indicating or measuring existing or desired position of tool or work {(B23Q16/005 takes precedence)} · CPC title