Form measuring apparatus and method of registering coordinate system for rotary table

Patent metadata

Field	Value
Publication number	US-9335143-B2
Application number	US-201414464224-A
Country	US
Kind code	B2
Filing date	Aug 20, 2014
Priority date	Aug 23, 2013
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

A form measuring apparatus includes a probe for measuring a measured object; a rotary table on which the measured object is placed; and a coordinate system calculator calculating coordinate axes configuring a coordinate system for the rotary table. The coordinate system calculator calculates, based on a position of a master ball fixated to the rotary table, a center of a circle traced by the master ball when the rotary table is rotated; calculates a rotary table coordinate system having the center of the circle as an origin point; and corrects coordinates of the origin point based on a calibrated diameter value of a gauge fixated to the rotary table, a first diameter value of the gauge measured by a first measurement in which the probe approaches the gauge in a first direction, and a second diameter value of the gauge measured by a second measurement.

First claim

What is claimed is:

1. A form measuring apparatus comprising:
a probe configured to measure a measured object;
a rotary table on which the measured object is to be placed and which is rotatable relative to the probe; and
a coordinate system calculator configured to:
calculate coordinate axes to establish a coordinate system for the rotary table;
calculate, based on a position of a master ball fixated to the rotary table, a center of a circle traced by the master ball when the rotary table is rotated;
calculate a coordinate system of the rotary table having the center of the circle as an origin point; and
correct coordinates of the origin point based on a calibrated diameter value of a gauge fixated to the rotary table, a first diameter value of the gauge measured by a first measurement in which the probe approaches the gauge in a first direction, and a second diameter value of the gauge measured by a second measurement in which the probe approaches the gauge in a second direction.

2. The form measuring apparatus according to claim 1 , wherein:
the probe is drivable so as to run parallel to each of an Xs axis, a Ys axis, and a Zs axis, which are mutually orthogonal,
a rotation axis of the rotary table is parallel to the Zs axis,
the first direction is parallel to the Xs axis, as viewed in the Zs axis direction, and
the second direction is parallel to the Ys axis, as viewed in the Zs axis direction.

3. The form measuring apparatus according to claim 2 , further comprising a coordinate system register configured to register the coordinate system of the rotary table, wherein:
the first measurement is a static point measurement, in which the probe approaches the gauge in the first direction in a case where the rotary table has a plurality of different rotation angles,
the second measurement is a static point measurement, in which the probe approaches the gauge in the second direction in a case where the rotary table has a plurality of different rotation angles,
the coordinate system calculator is further configured to calculate first corrected coordinates by correcting the coordinates of the origin point based on the calibrated diameter value, the first diameter value, and the second diameter value, and also calculates second corrected coordinates by correcting the coordinates of the origin point based on the calibrated diameter value, a third diameter value of the gauge measured by rotary table scanning measurement in which the probe approaches the gauge in a third direction parallel to the first direction, and a fourth diameter value of the gauge measured by rotary table scanning measurement in which the probe approaches the gauge in a fourth direction parallel to the second direction, and
the coordinate system register is further configured to register the first corrected coordinates as the coordinates of the origin point in the coordinate system of the rotary table to be used in clamp-on measurement, which measures a work piece fixated to the rotary table in a state where the rotary table is clamped so as to not rotate, and also registers the second corrected coordinates as the coordinates of the origin point in the coordinate system of the rotary table to be used in clamp-off measurement, which measures the work piece fixated to the rotary table in a state where the rotary table is not clamped.

4. The form measuring apparatus according to claim 3 , wherein:
the coordinate system of the rotary table includes a Z T axis corresponding to the rotation axis of the rotary table,
the coordinate system calculator is further configured to:
calculate, based on a position of a second master ball fixated to the rotary table, the center of a second circle traced by the second master ball when the rotary table is rotated, and
calculate the Z T axis based on the centers of the first and second circles, and

a distance from the rotary table to the first master ball is different from the distance from the rotary table to the second master ball.

5. The form measuring apparatus according to claim 2 , wherein:
the coordinate system of the rotary table includes a Z T axis corresponding to the rotation axis of the rotary table,
the coordinate system calculator is further configured to:
calculate, based on a position of a second master ball fixated to the rotary table, the center of a second circle traced by the second master ball when the rotary table is rotated, and
calculate the Z T axis based on the centers of the first and second circles, and

a distance from the rotary table to the first master ball is different from the distance from the rotary table to the second master ball.

6. The form measuring apparatus according to claim 1 , further comprising a coordinate system register configured to register the coordinate system of the rotary table, wherein:
the first measurement is a static point measurement, in which the probe approaches the gauge in the first direction in a case where the rotary table has a plurality of different rotation angles,
the second measurement is a static point measurement, in which the probe approaches the gauge in the second direction in a case where the rotary table has a plurality of different rotation angles,
the coordinate system calculator is further configured to calculate first corrected coordinates by correcting the coordinates of the origin point based on the calibrated diameter value, the first diameter value, and the second diameter value, and also calculates second corrected coordinates by correcting the coordinates of the origin point based on the calibrated diameter value, a third diameter value of the gauge measured by rotary table scanning measurement in which the probe approaches the gauge in a third direction parallel to the first direction, and a fourth diameter value of the gauge measured by rotary table scanning measurement in which the probe approaches the gauge in a fourth direction parallel to the second direction, and
the coordinate system register is further configured to register the first corrected coordinates as the coordinates of the origin point in the coordinate system of the rotary table to be used in clamp-on measurement, which measures a work piece fixated to the rotary table in a state where the rotary table is clamped so as to not rotate, and also registers the second corrected coordinates as the coordinates of the origin point in the coordinate system of the rotary table to be used in clamp-off measurement, which measures the work piece fixated to the rotary table in a state where the rotary table is not clamped.

7. The form measuring apparatus according to claim 6 , wherein:
the coordinate system of the rotary table includes a Z T axis corresponding to the rotation axis of the rotary table,
the coordinate system calculator is further configured to:
calculate, based on a position of a second master ball fixated to the rotary table, the center of a second circle traced by the second master ball when the rotary table is rotated, and
calculate the Z T axis based on the centers of the first and second circles, and

a distance from the rotary table to the first master ball is different from the distance from the rotary table to the second master ball.

8. The form measuring apparatus according to claim 1 , wherein:
the coordinate system of the rotary table includes a Z T axis corresponding to the rotation axis of the rotary table,
the coordinate system calculator is further configured to:
calculate, based on a position of a second master ball fixated to the rotary table, the center of a second circle traced by the second master ball when the rotary table is rotated, and
calculate the Z T axis based on the centers of the first and second circles, and

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Assignees

• Mitutoyo Corp

Inventors

• Noda Takashi
• Kamitani Hiroshi
• Usui Tomohiro

Classifications

• G01C25/00

  Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass (testing, calibrating or compensating compasses G01C17/38) · CPC title

• G01B5/008

  using coordinate measuring machines · CPC title

• G01B5/012 Primary

  Contact-making feeler heads therefor · CPC title

• G01B21/042 Primary

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