CNC Non-Contact Sensor Recalibration Using a Single Reference Sphere
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Solution Overview
Problem
Conventional CNC processing apparatuses require lengthy calibration procedures due to slight clearance between sensor mounting holders and spindles, necessitating frequent recalibration of sensor positions for accurate three-dimensional profile measurement.
Innovation Solution
A method that reduces calibration time by using a contact probe to measure center coordinates of a reference sphere, allowing for adjustments in non-contact sensor positions, and subsequent calibrations focus only on rotational adjustments about the Z-axis, minimizing the need for multiple measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration methods measuring center coordinates of at least three spheres are used, then measurement accuracy is ensured, but calibration time becomes excessively long
Solution Approach 1:
The patent extracts only the essential calibration information needed from the reference sphere by measuring its outer diameter and calculating the center coordinates mathematically, rather than measuring multiple spheres. This reduces the calibration process to measuring a single reference sphere's outer diameter and computing its center, significantly reducing calibration time while maintaining measurement accuracy
Solution Approach 2:
The patent performs preliminary calibration by measuring the reference sphere's outer diameter and calculating center coordinates before actual workpiece measurement. This preliminary action establishes the sensor's position relationship with the spindle, enabling accurate subsequent measurements without requiring time-consuming multi-sphere calibration procedures
2Measurement precision
If sensor position is calibrated each time tool is replaced with sensor, then measurement accuracy is maintained, but operation time increases significantly
Solution Approach 1:
The patent implements a self-calibration mechanism where the system automatically calculates the sensor's center coordinates based on the measured reference sphere outer diameter and predetermined relationships. This self-service approach eliminates the need for manual recalibration operations each time the sensor is mounted, maintaining accuracy while improving operational efficiency
Solution Approach 2:
The patent replaces manual mechanical calibration operations with automated computational calculations. Instead of physically adjusting and measuring multiple spheres, the system uses mathematical calculations based on the reference sphere's outer diameter and predetermined geometric relationships to determine sensor position, significantly reducing calibration time
3Adaptability or versatility
If clearance exists between sensor mounting holder and spindle mounting hole, then sensor replacement is possible, but sensor position stability deteriorates
Solution Approach 1:
The patent compensates for the position instability caused by clearance by dynamically calculating and adjusting the sensor's center coordinates based on actual measurements of the reference sphere. Instead of relying on fixed mechanical positioning, the system uses parameter changes in the coordinate calculation to adapt to slight position variations, maintaining measurement accuracy despite replaceability
Solution Approach 2:
The patent implements a feedback mechanism where the measured outer diameter of the reference sphere and the calculated center coordinates are used to adjust and refine the sensor's position parameters. This feedback loop compensates for position instability introduced by clearance, ensuring accurate measurements while maintaining sensor replaceability
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
Significantly reduces the operation time required for sensor calibration in CNC processing apparatuses, enhancing efficiency and accuracy of three-dimensional profile measurements.
Implementation Method 1
replaces the working tool with a non-contact sensor capable of measuring the distance to the surface using a laser beam
Data Source
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Figure 3~4(b)
Figure 5
AI summary
A method for calibrating a CNC processing apparatus is provided that can significantly reduce the amount of operation time required for sensor calibration. A method of the present invention for calibrating a non-contact sensor in a CNC processing apparatus 1 includes a first step, a second step and a third step. In the first step, the center coordinates of a reference instrument are measured with a contact probe and thereby the machine coordinates of the center of the reference instrument are determined. In the second step, after a non-contact sensor 110 is mounted onto a spindle 26, the center coordinates of the reference instrument are measured only one time with the non-contact sensor 110, and thereby the non-contact sensor coordinates of the center of the reference instrument are determined. In the third step, calculations are made to determine the amount of displacement required to bring the non-contact sensor coordinates obtained in the second step into agreement with the machine coordinates obtained with the contact probe in the first step.