Machine Tool Motion Error Mapping From Arbitrary Reference Positions
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Solution Overview
Problem
Current methods for measuring motion errors in machine tools, particularly perpendicularity errors, are limited as they cannot accurately identify errors with respect to the machine zero, requiring expensive equipment and complex operations, and do not allow for measurement beyond the machine zero.
Innovation Solution
A method to identify relative motion errors between a spindle and a table in a machine tool by measuring positioning, straightness, angular, and perpendicularity errors in a three-dimensional space using existing measurement methods, allowing for error data derivation at an arbitrary reference position, thus avoiding the need for expensive laser length measuring devices and simplifying the measurement process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods (laser length measuring device) are used to measure perpendicularity errors, then measurement precision is improved, but device cost and operational complexity increase significantly
Solution Approach 1:
The patent uses a double ball bar to measure perpendicularity errors by creating a simplified measurement model that copies the essential geometric relationship without requiring complex laser interferometry equipment. The double ball bar creates a physical replica of the perpendicularity relationship between axes that can be measured with simpler dial indicators or displacement sensors, thereby reducing device complexity while maintaining measurement capability
Solution Approach 2:
The double ball bar is a relatively simple, inexpensive measurement artifact compared to laser length measuring devices. It can be easily manufactured and replaced if needed, providing a cost-effective solution for perpendicularity error measurement that eliminates the need for expensive, complex laser-based measurement systems
2Measurement precision
If laser length measuring devices are used to measure motion errors, then measurement precision is improved, but measurement time and operational complexity increase
Solution Approach 1:
The double ball bar measurement method creates a simplified geometric model of the perpendicularity relationship that can be measured directly without requiring complex laser interferometry procedures. This copying approach reduces measurement time by eliminating the need for elaborate setup and measurement sequences required by laser devices
Solution Approach 2:
The patent measures perpendicularity errors at specific discrete positions using the double ball bar rather than attempting continuous measurement across the entire workspace. This partial measurement approach reduces measurement time while still capturing the essential error characteristics needed for compensation
3Stability of the object's composition
If measurement is performed with respect to machine zero, then coordinate system consistency is improved, but measurement flexibility and adaptability decrease
Solution Approach 1:
The patent derives perpendicularity errors with respect to an arbitrary reference position rather than being constrained to machine zero. This universal approach allows the same measurement data to be used for multiple purposes: compensation at the measured position, compensation at machine zero through coordinate transformation, and adaptation to different workpiece setups, thereby increasing versatility while maintaining coordinate consistency through mathematical transformation
Data Source
AI summary
A motion error of a machine tool in a coordinate system having its origin at an arbitrary position is identified by means of error data measured by a commonly-used method. An X-axis feed mechanism, a Y-axis feed mechanism, and a Z-axis feed mechanism are operated in a three-dimensional space of a machine coordinate system to measure translational errors, angular errors, and perpendicularity errors thereof, and error data for translational error parameters, angular error parameters, and perpendicularity error parameters in a three-dimensional space of a set coordinate system having its origin at a preset reference position Xa, Ya, Za are derived based on the measured actual error data. Subsequently, a relative motion error between a spindle and a table in the three-dimensional space of the set coordinate system is derived based on the derived error data.