Coordinate measuring machine and coordinate correction method

Patent metadata

Field	Value
Publication number	US-10422636-B2
Application number	US-201715681926-A
Country	US
Kind code	B2
Filing date	Aug 21, 2017
Priority date	Aug 26, 2016
Publication date	Sep 24, 2019
Grant date	Sep 24, 2019

Abstract

A processing device includes: a pushing drive mechanism control unit that brings a measurement tip into contact with a surface of a calibration artifact at a single point in each of five directions are all normal directions to the surface of the calibration artifact; a scanning drive mechanism control unit that reciprocates the measurement tip on the surface of the calibration artifact on each of three planes perpendicular to one another; a coordinate acquisition unit that acquires a moving amount and a probe output of a measuring probe; a matrix generation unit that generates a correction matrix; and a probe output correction unit that corrects the probe output with the correction matrix. This enables an improvement in asymmetric probe characteristics of the probe output, which is outputted from the measuring probe, in a particular plane. Thus, shape coordinates of an object to be measured can be obtained with high accuracy.

First claim

What is claimed is:

1. A coordinate measuring machine comprising:
a measuring probe that movably supports a stylus having a measurement tip to be brought into contact with an object to be measured, and that provides a probe output according to a displacement of the measurement tip;
a driver that moves the measuring probe relative to the object to be measured;
a calibration artifact with which the measurement tip is brought into contact; and
a processor that computes shape coordinates of the object to be measured on a basis of the probe output and a moving amount of the measuring probe by the driver, wherein the processor comprises, as a configuration when the processor executes instructions stored in a memory:
a pushing driver controller that controls the driver to bring the measurement tip into contact with a surface of the calibration artifact at a single point in each of five directions so that the five directions including three directions perpendicular to one another, and two directions among the three directions adding a respective inversed direction, are all normal directions to the surface of the calibration artifact, to push the calibration artifact with the measurement tip by a predetermined displacement amount, and then to move the measurement tip in an opposite direction to separate the measurement tip away from the surface;
a scanning driver controller that controls the driver to reciprocate the measurement tip on the surface of the calibration artifact while pressing the calibration artifact with the measurement tip by a constant deflection amount on each of three planes perpendicular to one another;
a coordinate acquisition processor that acquires the moving amount and the probe output of the measuring probe when the measurement tip engages with the calibration artifact by the pushing driver controller and the scanning driver controller;
a matrix generator that generates a correction matrix for correcting the probe output with respect to the moving amount of the measuring probe on a basis of an output of the coordinate acquisition processor; and
a probe output corrector that corrects the probe output with the correction matrix.

2. The coordinate measuring machine according to claim 1 , wherein the five directions include: an axial direction of the stylus; two directions perpendicular to each other in a plane perpendicular to the axial direction; and two directions having measurement forces opposite to those of the two directions perpendicular to each other.

3. The coordinate measuring machine according to claim 2 , wherein:
the driver includes an X-axis driver, a Y-axis driver, and a Z-axis driver that move the measuring probe, and
when the axial direction coincides with a moving direction of any one of the X-axis driver, the Y-axis driver, and the Z-axis driver, two moving directions of the remaining drivers and the two directions perpendicular to each other in the plane perpendicular to the axial direction are shifted from each other by an angle of 45 degrees.

4. A coordinate correction method of a coordinate measuring machine, the coordinate measuring machine including: a measuring probe for movably supporting a stylus having a measurement tip to be brought into contact with an object to be measured and for providing a probe output according to a displacement of the measurement tip; a drive mechanism for moving the measuring probe relative to the object to be measured; and a processing device for computing shape coordinates of the object to be measured on a basis of the probe output and a moving amount of the measuring probe by the drive mechanism, the coordinate correction method comprising:
a first controlling of the drive mechanism to bring the measurement tip into contact with a surface of a calibration artifact at a single point in each of five directions so that the five directions including three directions perpendicular to one another, and two directions among the three directions adding a respective inversed direction, are all normal directions to the surface of the calibration artifact, to push the calibration artifact with the measurement tip by a predetermined displacement amount, and then to move the measurement tip in an opposite direction to separate the measurement tip away from the surface;
a second controlling of the drive mechanism to reciprocate the measurement tip on the surface of the calibration artifact while pressing the calibration artifact with the measurement tip by a constant deflection amount on each of three planes perpendicular to one another;
acquiring the moving amount and the probe output of the measuring probe when the measurement tip engages with the calibration artifact in the first and second controlling of the drive mechanism;
generating, on a basis of the acquired moving amount and the acquired probe output of the measuring probe, a correction matrix for correcting the probe output with respect to the moving amount of the measuring probe; and
correcting the probe output with the correction matrix.

5. The coordinate correction method according to claim 4 , wherein the five directions include: an axial direction of the stylus; two directions perpendicular to each other in a plane perpendicular to the axial direction; and two directions having measurement forces opposite to those of the two directions perpendicular to each other.

6. The coordinate correction method according to claim 5 , wherein:
the drive mechanism includes an X-axis drive mechanism, a Y-axis drive mechanism, and a Z-axis drive mechanism for moving the measuring probe, and
when the axial direction coincides with a moving direction of any one of the X-axis drive mechanism, the Y-axis drive mechanism, and the Z-axis drive mechanism, two moving directions of the remaining drive mechanisms and the two directions perpendicular to each other in the plane perpendicular to the axial direction are shifted from each other by an angle of 45 degrees.

Assignees

• Mitutoyo Corp

Inventors

• Nakagawa Hideyuki
• Ishikawa Nobuhiro

Classifications

• G01B5/008 Primary

  using coordinate measuring machines · CPC title

• G01B21/042

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

• G01B21/045 Primary

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

• G01B21/047

  Accessories, e.g. for positioning, for tool-setting, for measuring probes · CPC title

• G01B5/016

  Constructional details of contacts · CPC title