Coordinate Measuring Machine Probe Head Deformation Correction
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Solution Overview
Problem
Coordinate measuring machines experience systematic errors due to the deformation of probe heads and structural components during measurement, which are not adequately accounted for in existing correction methods, and the flexibility of calibration bodies and workpieces also introduces measurement errors.
Innovation Solution
Determine the mechanical flexibility of calibration bodies and workpieces, store this data, and use it to correct measured values by point-by-point scanning and calibration, incorporating the flexibility into the correction process to account for deformations and improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the probe applies probing force to measure workpiece surfaces, then measurement capability is achieved, but the probe head and stylus bend causing measurement errors
Solution Approach 1:
The patent performs preliminary calibration by measuring a calibration body with known geometric characteristics before actual workpiece measurement. During calibration, the probe approaches the calibration body surface at multiple positions and orientations, recording measured values that are then used to calculate deformation parameters. These pre-determined parameters are stored and applied to subsequent measurements to compensate for probe head bending caused by probing force.
2Measurement precision
If the probe is calibrated using conventional methods, then probe calibration is achieved, but the calibration body and holder deform under probing force introducing errors
Solution Approach 1:
The patent determines deformation parameters by analyzing the relationship between measured coordinate values and the known actual coordinate values of the calibration body. The calibration process calculates correction values based on the difference between measured and actual positions, accounting for the deformation that occurs during calibration. These deformation parameters are then stored and applied to compensate for similar deformations during actual workpiece measurement.
3Measurement precision
If the workpiece is flexible and deforms under probe contact, then measurement of surface geometry is achieved, but deformation of the workpiece itself introduces measurement errors
Solution Approach 1:
The patent applies feedback correction by using the determined deformation parameters to adjust measured values. The deformation parameters, calculated from calibration measurements, provide information about the expected deformation behavior. During workpiece measurement, these parameters are used to correct the measured coordinate values, compensating for workpiece deformation under probe contact and improving measurement accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively compensates for errors caused by calibration body and workpiece deformations, ensuring accurate measurements by accounting for their flexibility and reducing measurement errors.
Implementation Method 1
the usual probing forces also deform the calibration bodies and their holders to a degree that is no longer negligible
Implementation Method 2
calculate correction values from this, with the help of which the measuring errors due to machine bending can be compensated
Data Source
Figure 1
Figure 2~3
AI summary
A method is used to correct measured values of a coordinate measurement device having a probe head (6), a calibrating body and an apparatus (10, 30) for recording and correcting measured values (xi, yi, zi) recorded by the probe head (6) on the basis of predetermined deformation parameters of elements of the coordinate measurement device. Said method comprises the steps of: a) determining the mechanical compliance at predetermined points (28) on the surface (26) of the calibrating body; b) storing the compliance which has been determined in the apparatus in the form of a data record (N); c) using the probe head (6) to scan the calibrating body point by point; and d) calibrating the probe head (6) by correcting the measured values of the probe head (6), which are determined in step c), using the data record (N). The method can similarly also be used on workpieces with a known compliance. A coordinate measurement device which is suitable for carrying out these methods is also proposed.