Rotary Table Coordinate Registration with Axis Run-Out Compensation
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Solution Overview
Problem
Existing methods for registering a rotary table coordinate system in coordinate measuring machines are prone to errors due to run-out in the rotation axis, particularly when measuring cylindrical shafts at different positions, leading to inaccuracies in the origin point registration.
Innovation Solution
A method that calculates corrected coordinates for the origin point of the rotary table coordinate system using calibrated and measured diameter values from multiple directions, incorporating the positions of master balls at different distances from the table surface, and adjusts the Z-axis based on the centers of circles traced by these balls to account for axis run-out, allowing for accurate registration in both 'clamp on' and 'clamp off' measurement scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the traditional method of registering the rotary table coordinate system using a single master ball is used, then the registration process is simple, but measurement accuracy deteriorates due to axis run-out errors
Solution Approach 1:
The patent divides the coordinate system registration into two independent parts: (1) determining the Z-axis direction using a master ball, and (2) determining the origin point using a gauge. This segmentation allows each part to be optimized independently - the Z-axis registration remains simple while the origin point registration achieves high accuracy through multiple measurement directions.
Solution Approach 2:
The patent introduces a gauge as an intermediary object between the master ball and the final origin point determination. The gauge serves as a mediator that enables accurate origin point registration by providing multiple measurement directions, while the master ball continues to serve as the intermediary for Z-axis determination.
2Reliability
If multiple master balls at different distances from the table surface are used to calculate the Z-axis, then axis run-out errors are reduced, but the registration process becomes more complex
Solution Approach 1:
The patent extracts the Z-axis determination function from the origin point determination process. By separating these two functions, the system can use multiple master balls for Z-axis calculation to achieve run-out error compensation, while the origin point is determined separately using a gauge, preventing the complexity from compounding both steps.
Solution Approach 2:
The patent transitions from determining the origin point in a single dimension (using one master ball) to determining it through multiple dimensions (using a gauge measured in multiple directions). This dimensional expansion enables accurate origin point registration while maintaining separate, optimized processes for Z-axis and origin point determination.
3Measurement precision
If the origin point coordinates are not corrected using multiple diameter measurements, then the registration process is faster, but measurement accuracy deteriorates
Solution Approach 1:
The patent performs preliminary measurements of the gauge in multiple directions to calculate corrected origin point coordinates before actual workpiece measurement. This preliminary action establishes an accurate corrected origin point that compensates for axis run-out, enabling subsequent measurements to achieve high accuracy without repeating the complex multi-directional calculation process for each measurement.
Data Source
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AI summary
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 fixed 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 fixed 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.