Coordinate measuring machine (CMM) and method of compensating errors in a CMM

Patent metadata

Field	Value
Publication number	US-9435645-B2
Application number	US-201013148938-A
Country	US
Kind code	B2
Filing date	Feb 11, 2010
Priority date	Feb 11, 2009
Publication date	Sep 6, 2016
Grant date	Sep 6, 2016

Abstract

The present invention relates to a coordinate measuring machine comprising a stationary base, a probe head, at least one linear drive mechanism for moving in a first direction, the linear drive mechanism having a linear guide and a movable member being supported for movement along the guide by bearings. The linear drive mechanism further comprises at least a first pre-calibrated integral sensor-package having at least two displacement sensors each for measuring a distance from the movable member to the guide in a direction being non-parallel with respect to the first direction, wherein the sensed distances indicate a translational displacement of the movable member from an ordinary bearing position in a direction perpendicular to the first direction and a rotational displacement of the movable member.

First claim

What is claimed is:

1. A coordinate measuring machine for determination of at least one space coordinate of a measurement point on an object to be measured, comprising:
a stationary base;
a probe head being moveable relative to the base;
at least one linear drive mechanism for provision of movability of the probe head relative to the base in a first direction, the linear drive mechanism including:
a linear guide in the first direction;
a movable member being supported for movement along the linear guide by bearings provided between mutually facing surface of the linear guide and the moving member; and
a linear measuring instrument for determination of a first drive position of the movable member in the first direction in parallel to the linear guide;
a calculation unit for determination of the space coordinate as a function of at least the first drive position;
at least a first pre-calibrated integral sensor-package having at least two displacement sensors each being built for measuring a distance from the movable member to the linear guide in a direction being non-parallel with respect to the first direction, in particular bearing distances between mutually facing surfaces of the movable member and the linear guide, wherein:
the first pre-calibrated integral sensor-package comprises a common housing for rigidly joining together the displacement sensors with a precisely known spatial and geometrical relationship of the displacement sensors relative to each other and the first integral sensor package is built modular and forms a one-piece, coherent component in such a way that it is mountable to and removable from the coordinate measuring machine en bloc;
the sensed distances indicate a translational displacement of the movable member from an ordinary bearing position in a direction perpendicular to the first direction; and a rotational displacement of the movable member; and
the space coordinate is determined by the calculation unit is further dependent on the indicated displacement.

2. The coordinate measuring machine according to claim 1 , wherein the displacement sensors are built as optical, capacitive or inductive displacement sensor.

3. The coordinate measuring machine according to claim 1 , wherein the bearings are built as air bearings.

4. The coordinate measuring machine according to claim 1 , wherein the linear guide comprises a first and a second surface building an edge extending in parallel to the first direction, wherein the movable member having first and second surfaces mutually facing towards the two surfaces of the linear guide, particularly wherein an air cushion being between the mutually facing first surfaces and the mutually facing second surfaces.

5. The coordinate measuring machine according to claim 4 , wherein the first pre-calibrated integral sensor-package comprises three displacement sensors and is arranged on the first inner surface of the movable member for measuring three distances from the first inner surface of the movable member to the first outer surface of the guide.

6. The coordinate measuring machine according to claim 5 , wherein
a second integral sensor-package including at least two displacement sensors is arranged on the second surface of the movable member for measuring two distances from the second surface of the movable member to the second surface of the guide;
the distances sensed by the displacement sensors of the first and second integral sensor packages indicate:
two translational displacements of the movable member from an ordinary bearing position in two directions of which one being perpendicular to the first inner surface and the other being perpendicular to the second inner surface of the movable member; and
three rotational displacements of the movable member about three axis of which one axis being parallel to the first direction, one axis being perpendicular to the first inner surface and one axis being perpendicular to the second inner surface of the movable member; and

the space coordinate is determined further dependent on the two translational and three rotational displacements.

7. The coordinate measuring machine according to claim 1 , wherein the housing of the sensor-package comprises a frame structure built up from bracing struts so as to allow for high geometrical stability and constant spatial relationship of the displacement sensors relative to each other.

8. The coordinate measuring machine according to claim 1 , wherein the housing of the sensor-package comprises a frame structure built up from bracing struts, and the housing or the frame structure consists of, or comprises, invar or carbon fiber material, so as to allow for high geometrical stability and constant spatial relationship of the displacement sensors relative to each other.

9. The coordinate measuring machine according to claim 1 , wherein the coordinate measuring machine is built for determination of three space coordinates of the measurement point and comprises:
three linear drive mechanisms for provision of movability of the probe head relative to the base in the first, a second and a third direction each linear drive mechanism including:
a linear guide in the first, the second respectively the third direction;
a movable member being supported for movement along the guide by bearings;
a linear measuring instrument for determination of the first, a second or a third drive position, respectively, of the movable member in the first, the second or the third direction in parallel to the linear guide, respectively, and
at least one pre-calibrated integral sensor package including at least two displacement sensors, for indicating at least one translational and one rotational displacement of the movable member from an ordinary bearing position,

wherein the calculation unit is designed for determining the three space coordinates as a function of the first, the second and the third drive position and the sensed displacements of each moving member.

10. The coordinate measuring machine according to claim 9 , wherein at least one pre-calibrated integral sensor package including at least two displacement sensors, is designed for indicating two translational and three rotational displacements, of the movable member from an ordinary bearing position.

11. The coordinate measuring machine according to claim 1 , wherein the coordinate measuring machine is designed according to one of the following styles:
bridge-type;
L-bridge-type;
horizontal-arm-type;
cantilever-type; or gantry-type.

12. The coordinate measuring machine according to claim 1 , wherein:
a contact probe, or a non-contact probe, capacitance probe, or inductance probe, is arranged on the probe head and/or
the base comprises a table with a granite surface plate for supporting the object to be measured.

13. The coordinate measuring machine according to claim 1 , wherein:
a scanning, touch trigger probe, or an optical probe is arranged on the probe head.

14. The coordinate measuring machine according to claim 1 , wherein at least the first pre-calibrated integral sensor-package includes at least two displacement sensors each being built for measuring bearing distances between mutually facing surfaces of the movable member and the guide.

15. A method of compensating errors in a coordinate measuring machine, which determines at least one space coordinate of a measurement point on an object to be measured, the coordinate measuring machine including at least one linear drive mechanism for provision of movability of a probe head in a first direction, with a linear guide in the first direction, a movable memb

Assignees

• Pettersson Bo
• Siercks Knut
• Leica Geosystems Ag

Inventors

• Pettersson Bo
• Siercks Knut

Classifications

• G01B7/008

  using coordinate measuring machines · CPC title

• G01B21/045 Primary

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

• G01B5/008

  using coordinate measuring machines · CPC title