Measuring Probe Calibration for Pivoting Axis Errors
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Solution Overview
Problem
Machine tools with pivoting axes suffer from inaccuracies due to angle errors and incorrect pivoting axis center positions, leading to discrepancies between calculated and actual positions of workpieces, tools, or measuring probes, especially under temperature variations.
Innovation Solution
A method that uses a calibrating body to determine a correction value for the actual position deviation, allowing for the correction of pivoting errors in both the measurement object and the measuring probe by subtracting or adding the deviation to the measured values, and applying this correction during the measurement process after clamping the pivoting axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pivoting axes are used to enable five-axis machining capabilities, then the versatility and functionality of the machine tool is improved, but the measurement precision and positioning accuracy deteriorate due to angle errors and incorrect pivoting axis center positions
Solution Approach 1:
The patent applies preliminary action by performing a calibration measurement before actual workpiece measurement. A calibrating body with known geometric properties is measured in the same pivoted positions that will be used for workpiece measurement, allowing determination of correction values in advance. These correction values compensate for pivoting axis errors during subsequent measurements, resolving the contradiction by preparing compensation data beforehand.
Solution Approach 2:
The patent implements feedback by using the measured positions of the calibrating body to calculate correction values that are then applied to subsequent measurements. The system continuously uses measurement feedback to adjust and compensate for pivoting errors, maintaining measurement precision despite the use of imperfect pivoting axes.
2Adaptability or versatility
If pivoting movements are performed to reach measuring points, then the ability to access complex workpiece geometries is improved, but the measurement precision deteriorates due to non-repeatable and inaccurate pivoting movements
Solution Approach 1:
The patent uses a calibrating body as a reference copy with precisely known geometric properties. By measuring this reference object in the same positions as the workpiece, the system creates a template of pivoting errors that can be copied and applied as corrections to all subsequent measurements, ensuring repeatability despite mechanical imperfections.
Solution Approach 2:
The patent changes the parameters used for calculation by applying correction values to the measured coordinates. Instead of relying solely on the raw pivoting axis positions, the system transforms the coordinate parameters using empirically determined corrections, thereby improving measurement repeatability while maintaining the ability to access complex geometries.
3Adaptability or versatility
If temperature variations occur during operation, then the adaptability of the machine to different environmental conditions is improved, but the measurement precision deteriorates due to thermal expansion and drift in pivoting axis positions
Solution Approach 1:
The patent performs calibration measurements under the actual environmental conditions before workpiece measurement. By determining correction values in the same temperature and environmental conditions as the actual measurement, the system compensates for thermal effects specific to that environment, maintaining precision despite temperature variations.
Data Source
AI summary
A method for measuring workpieces with a measuring probe on a machine tool with linear axes of motion and at least one pivoting axis is provided, whereby the deviation of an actual position of a calibrating body in a pivoted position, in relation to a theoretical pivoted position which the calibrating body ideally occupy without a pivoting error, is used to determine a correction value. An actual measured value for calculating a coordinate of a measuring point on a measurement object or a theoretical measuring-point coordinate to be approached on the measurement object is corrected using the correction value when a measurement is carried out on the measurement object in a corresponding pivoted position. A device for implementing the method is also provided.