Corrected ball diameter calculating method and form measuring instrument

• US 9,151,602 B2
• Filed: 03/24/2010
• Issued: 10/06/2015
• Est. Priority Date: 03/25/2009
• Status: Active Grant

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Noda, Takashi, Deguchi, Hiromi
• Primary Examiner(s): Kundu, Sujoy
• Assistant Examiner(s): Casey, Liam R
• Application Number:
  US12/730,534
• Publication Number:
  US 20100250178A1
• Time in Patent Office: 2,022 Days
• Field of Search: 702/157, 702/167, 702/168, 702/95
• US Class Current: 1/1
• CPC Class Codes: G01B 21/042 Calibration or calibration artifacts G01B3/30, G01B9/02072 take precedence
• CPC Class Codes: G01B 21/045 Correction of measurements G01B9/02055 takes precedence
• CPC Class Codes: G01B 5/008 using coordinate measuring machines
• CPC Class Codes: G01B 5/20 for measuring contours or curvatures
• CPC Class Codes: G01B 5/201 for measuring roundness
• CPC Class Codes: G01B 5/28 for measuring roughness or irregularity of surfaces

Abstract

A corrected ball diameter calculating method includes: preparing a reference gauge that has at least one reference peripheral surface of an outer peripheral surface and an inner peripheral surface; valuing of diameter values of the reference peripheral surface at a plurality of different height positions from a bottom surface of the reference gauge; calculating calibrated diameter values per each of the height positions; placing the reference gauge on the rotary table and causing the stylus tip to touch a plurality of measurement sites on the reference peripheral surface at each of the height positions to calculate measured diameter values that are diameter values of a circle passing through the neighborhood of center points of the stylus tip; and calculating the corrected ball diameters per each of the height positions from the calibrated diameter values and the measured diameter values that are calculated per each of the height positions.

Claims

1. A corrected stylus ball diameter calculating method for use in a form measuring instrument, the form measuring instrument including:

a rotary table on which an workpiece is placed;

a rotation angle sensor configured to detect the rotation angle of the rotary table;

a probe including a stylus ball; and

a coordinate value sensor configured to detect the coordinate values of the probe, the corrected stylus ball diameter calculating method comprising;

preparing a reference gauge that has an outer reference cylindrical surface and an inner reference cylindrical surface;

valuing of diameter values of the outer and inner reference cylindrical surfaces at a plurality of different height positions from a bottom surface of the reference gauge;

calculating calibrated diameter values of the outer and inner reference cylindrical surfaces per each of the height positions;

placing the reference gauge on the rotary table and causing the stylus ball to touch a plurality of measurement sites on the outer and inner reference cylindrical surfaces at each of the height positions;

point-measuring and profile-measuring, in a state where the reference gauge is caused to rotate by driving the rotary table, per each of the height positions, diameter values of a regression circle that fits a state of distribution of center points of the stylus ball when the stylus ball has touched each of the measurement sites of the outer reference cylindrical surface and the inner reference cylindrical surface to thereby determine outer diameters of the reference gauge by the point-measurement, outer diameters of the reference gauge by the profile-measurement, inner diameters of the reference gauge by the point-measurement, and inner diameters of the reference gauge by the profile-measurement at each of the height positions; and

calculating the corrected stylus ball diameters at each of the height positions based on the outer diameters of the reference gauge by the point-measurement, the outer diameters of the reference gauge by the profile-measurement, the inner diameters of the reference gauge by the point-measurement, and the inner diameters of the reference gauge by the profile-measurement at each of the height positions.

5. The corrected stylus ball diameter calculating method according to claim 1, wherein:

the reference gauge is a cylindrical square or a ring gauge.

6. The corrected stylus ball diameter calculating method according to claim 1, wherein:

the reference gauge is a cylindrical square.

7. The corrected stylus ball diameter calculating method according to claim 1, wherein:

the reference gauge is a ring gauge.

2. A form measuring instrument, comprising:

a rotary table rotatably disposed on which a workpiece is placed;

a rotation angle sensor configured to detect the rotation angle of the rotary table;

a probe including a stylus ball;

a moving mechanism configured to cause the probe to move;

a coordinate value sensor configured to detect the coordinate values of the probe;

a controller configure to control the rotary table and the moving mechanism to cause the stylus ball to touch the workpiece; and

an analyzer configured to use detected values that are detected by each of the sensors when the stylus ball is caused to touch the workpiece by the controller and corrected stylus ball diameters that are calculatory diameter values of the stylus ball to analyze the profile of the workpiece, the analyzer comprising;

a storage unit configured to store beforehand calibrated diameter values that is calculated per each height position by performing, with respect to a reference gauge that has an outer reference cylindrical surface and an inner reference cylindrical surface, valuing of diameter values of the outer and inner reference cylindrical surfaces of the reference gauge at a plurality of different height positions from a bottom surface of the reference gauge;

a measured diameter value calculating unit configured to calculate, per each of the height positions, measured diameter values that are diameter values of a regression circle that fits a state of distribution of center points of the stylus ball when the stylus ball has touched each measurement site of the outer and inner reference cylindrical surfaces as a result of the stylus ball being caused to touch a plurality of measurement sites on the outer and inner reference cylindrical surfaces of the reference gauge at each of the height positions in a state where the reference gauge is placed on the rotary table and rotated to thereby determine outer diameters of the reference gauge by point-measurement, outer diameters of the reference gauge by profile-measurement, inner diameters of the reference gauge by point-measurement, and inner diameters of the reference gauge by profile-measurement at each of the height positions;

a corrected stylus ball diameter calculating unit configured to calculate the corrected stylus ball diameters based on the outer diameters of the reference gauge by the point-measurement, the outer diameters of the reference gauge by the profile-measurement, the inner diameters of the reference gauge by the point-measurement, and the inner diameters of the reference gauge by the profile-measurement at each of the height positions; and

an analyzing unit configured to use the corrected stylus ball diameters to calculate the profile of the workpiece.

3. The form measuring instrument according to claim 2, wherein:

the analyzing unit further comprises;

an analysis-use corrected stylus ball diameter calculating unit configured to calculate, from the corrected stylus ball diameters that are calculated per each of the height positions, analysis-use corrected stylus ball diameters that are used when analyzing the workpiece; and

a workpiece analyzing unit configured to use the analysis-use corrected stylus ball diameters to analyze the profile of the workpiece; and

the analysis-use corrected stylus ball diameter calculating unit calculates, from the corrected stylus ball diameters that are calculated per each of the height positions, approximate functions whose variables are height positions that are measured and calculates, from the approximate functions, analysis-use corrected stylus ball diameters corresponding to height positions of the workpiece that the controller measures.

4. The form measuring instrument according to claim 2, wherein:

the analyzing unit further comprises;

an analysis-use corrected stylus ball diameter calculating unit configure to calculate, from the corrected stylus ball diameters that are calculated per each of the height positions, analysis-use corrected stylus ball diameters that are used when analyzing the workpiece; and

a workpiece analyzing unit configured to use the analysis-use corrected stylus ball diameters to analyze the profile of the workpiece; and

the analysis-use corrected stylus ball diameter calculating unit calculates, as the analysis-use corrected stylus ball diameters, average values of the corrected stylus ball diameters that are calculated per each of the height positions.

8. The form measuring instrument according to claim 2, wherein:

the reference gauge is a cylindrical square or a ring gauge.

9. The form measuring instrument according to claim 2, wherein:

the reference gauge is a cylindrical square.

10. The form measuring instrument according to claim 2, wherein:

the reference gauge is a ring gauge.