CORRECTED BALL DIAMETER CALCULATING METHOD AND FORM MEASURING INSTRUMENT

• US 20100250178A1
• Filed: 03/24/2010
• Published: 09/30/2010
• Est. Priority Date: 03/25/2009
• Status: Active Grant

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Noda, Takashi, Deguchi, Hiromi
• Granted Patent: US 9,151,602 B2
• Time in Patent Office: Days
• US Class Current: 702/95
• 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 ball diameter calculating method for use in a form measuring instrument, the form measuring instrument including:

a rotary table rotatably disposed and adapted an workpiece to be placed;

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

a probe including a stylus tip; and

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

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 in a state where the reference gauge is caused to rotate by driving the rotary table, to calculate, per each of the height positions, measured diameter values that are diameter values of a circle passing through the neighborhood of center points of the stylus tip when the stylus tip has touched each of the measurement sites; 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.

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

the reference peripheral surface is point-measured and profile-measured to calculate measured diameter values resulting from point measurement and measured diameter values resulting from scanning measurement; and

corrected ball diameters resulting from point measurement and corrected ball diameters resulting from scanning measurement are calculated from the calibrated diameter values and from the measured diameter values resulting from point measurement and the measured diameter values resulting from scanning measurement.

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

the outer peripheral surface and the inner peripheral surface of the reference gauge are measured to thereby calculate measured diameter values resulting from measurement of the cuter peripheral surface and measured diameter values resulting from measurement of the inner peripheral surface; and

corrected ball diameters resulting from measurement of the outer peripheral surface and corrected ball diameters resulting from measurement of the inner peripheral surface are calculated from the calibrated diameter values and from the measured diameter values resulting from measurement of the outer peripheral surface and the measured diameter values resulting from measurement of the inner peripheral surface.

4. A form measuring instrument, comprising:

a rotary table rotatably disposed and adapted an workpiece to be placed;

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

a probe including a stylus tip;

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 tip to touch the workpiece; and

an analyzer configured to use detected values that are detected by each of the sensors when the stylus tip is caused to touch the workpiece by the controller and corrected ball diameters that are calculatory diameter values of the stylus tip 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 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 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 circle passing through the neighborhood of center points of the stylus tip when the stylus tip has touched each measurement site as a result of the stylus tip being caused to touch a plurality of measurement sites on the reference peripheral surface 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;

a corrected ball diameter calculating unit configured to calculate 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; and

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

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

the analyzing unit further comprises;

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

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

the analysis-use corrected ball diameter calculating unit calculates, from the corrected 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 ball diameters corresponding to height positions of the workpiece that the controller measures.

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

the analyzing unit further comprises;

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

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

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