Machine Tool Axis Compensation Using Curve-Fit Error Calibration
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Solution Overview
Problem
Existing machine tool compensation methods are complex for unskilled operators and result in motion errors due to measurement variation, particularly when using calibration masters for error compensation.
Innovation Solution
A method for compensating motion errors in machine tools involves outputting calibration-master conditions, installing and measuring calibration masters, calculating error values, and approximating compensation parameters using curves and straight lines to reduce measurement variation and improve accuracy across the entire range of motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a touch probe is used for measuring a reference straight line portion of a master block and the measurement result is directly used as a compensation amount, then the compensation control can be performed, but the measurement variation causes a motion error
Solution Approach 1:
The patent applies preliminary action by pre-calculating compensation parameters through curve approximation before actual machining operations. The measurement results are processed through curve fitting to predict compensation amounts, rather than directly using raw measurements. This preliminary processing of measurement data eliminates the direct transmission of measurement variations to motion errors.
2Measurement precision
If a calibration master is used for measuring the error of the translational axis, then the measurement can be performed, but it requires an operator to consider which calibration masters to install and how to install them, which is a difficult work for an unskilled operator
Solution Approach 1:
The system applies self-service by automatically selecting and installing the appropriate calibration master based on the measurement requirements. The control device determines which calibration master should be used and performs the installation automatically, eliminating the need for operators to manually decide which calibration master to install and how to install it.
Solution Approach 2:
The patent replaces the manual mechanical process of selecting and installing calibration masters with an automated control system. The control device uses computational logic to select the appropriate calibration master and automates the installation process, substituting human judgment and manual operation with automated mechanical and computational systems.
3Manufacturing precision
If the compensation parameter is calculated based on measurement results in the entire stroke range, then the compensation accuracy can be improved, but the measurement time and complexity increase
Solution Approach 1:
The patent applies partial action by measuring errors only in specific partial ranges of the translational axis stroke rather than the entire range. The control device divides the stroke into multiple ranges and performs measurements only in selected partial ranges, then uses curve approximation to extrapolate compensation parameters for the full range. This reduces measurement time while maintaining compensation accuracy through mathematical interpolation.
Data Source
AI summary
An error compensation method includes outputting at least one of a plurality of calibration-master conditions including a type of a calibration master that includes targets, obtaining measurement values of positions of the targets by detecting the positions of the plurality of targets under the calibration-master condition using a sensor mounted to the main spindle, and calculating an error value using the measurement value and a calibration value of the position of the target. The error compensation method further includes approximating a relation between the measurement values and the error values by a curve and a straight line, calculating a compensation parameter of a positioning error of a translational axis based on an approximate curve in a partial range of a stroke of the translational axis, and calculating the compensation parameter of the positioning error based on an approximate straight line in another range of the stroke of the translational axis.