On-board Probe Temperature Drift Correction
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Solution Overview
Problem
Existing three-dimensional measuring machines suffer from temperature drift errors due to thermal expansion, especially in on-board measuring machines used for ultraprecision machining, which can lead to significant measurement inaccuracies when measuring non-axisymmetric workpieces over extended periods.
Innovation Solution
A method involving an on-board measuring machine with a touch probe supported by a fluid bearing, utilizing a numerical controller to correct temperature drift by setting a reference point and resetting probe position data before each measurement path, allowing for continuous temperature drift correction during shape measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If measurement is performed for a long time to measure the whole face of the workpiece, then measurement coverage is improved, but temperature drift error increases
Solution Approach 1:
The patent applies preliminary action by measuring reference points (including intersecting points of scanning lines) before performing the main shape measurement of the workpiece. These reference point measurements are used to calculate temperature drift amounts in advance, which are then used to correct the shape measurement data. This preliminary measurement and correction approach allows long-duration comprehensive measurement while compensating for temperature drift effects.
Solution Approach 2:
The patent implements feedback by continuously measuring reference points during the shape measurement process, calculating temperature drift amounts from these measurements, and using the calculated drift amounts to correct subsequent shape measurement data. This closed-loop feedback mechanism enables real-time compensation for temperature drift, maintaining measurement precision even during extended measurement periods covering large workpiece areas.
2Measurement precision
If scanning speed is reduced to improve measurement precision, then measurement resolution is improved, but measurement time increases
Solution Approach 1:
The patent performs preliminary measurement of reference points at lower scanning speeds to ensure high measurement resolution and accuracy. These reference point measurements establish a precise coordinate system and enable calculation of temperature drift characteristics. By concentrating the slow, high-precision measurements on reference points rather than the entire workpiece surface, the system achieves high overall measurement precision while reducing total measurement time.
Solution Approach 2:
The patent applies partial action by performing high-precision slow scanning only on reference points (intersecting points of scanning lines) rather than on the entire workpiece surface. The majority of the workpiece measurement can be performed at higher scanning speeds with the benefit of temperature drift correction applied afterward. This selective application of slow scanning to critical reference points achieves the necessary measurement resolution while significantly reducing total measurement time.
3Reliability
If temperature control is strengthened to reduce temperature drift, then measurement stability is improved, but device complexity increases
Solution Approach 1:
The patent implements feedback by measuring reference points during the measurement process, calculating temperature drift amounts from these measurements, and using the calculated drift amounts to correct shape measurement data. This measurement-based feedback approach to temperature drift compensation achieves high measurement stability without requiring complex active temperature control systems, environmental chambers, or thermal isolation equipment.
Solution Approach 2:
The patent replaces mechanical/thermal temperature control systems with a computational approach. Instead of using complex temperature control hardware, environmental control chambers, or thermal isolation mechanisms, the system uses software-based temperature drift correction that calculates drift amounts from reference point measurements and applies mathematical corrections to the shape measurement data. This substitution of physical temperature control with computational correction significantly reduces device complexity while maintaining measurement stability.
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 stabilizes measurement accuracy over long times by resetting temperature drift corrections after each measurement path, ensuring nanoscale precision even in environments with minor temperature fluctuations, thus preventing fatal errors in ultraprecision machining.
Implementation Method 1
a touch probe (1e) supported by a fluid bearing
Implementation Method 2
The error in the measurement value is mainly caused by thermal expansion or thermal contraction of the members forming the three-dimensional measuring machine
Data Source
AI summary
In a machine tool having an on-board measuring machine and controlled by a numerical controller, a method of measuring a shape of a workpiece presets a reference point for temperature drift correction on the workpiece, moves a probe to the reference point, resets a coordinate system of the probe to correct a temperature drift of the probe, and carries out shape measurement of the workpiece along a first measuring path. Next, the method moves the probe to the reference point again, resets the coordinate system of the probe to correct a temperature drift of the probe again, and carries out shape measurement of the workpiece along a second measuring path. Thereafter, similar temperature drift correction is carried out for each measuring path until the shape measurement of the workpiece is carried out along the last measuring path.