Machine Tool Geometric Error Identification in Limited Travel Axes
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Solution Overview
Problem
Existing methods for evaluating geometric errors in spindle-moving lathes with limited movable ranges, such as ball bar measurement and R-test measurement, are not applicable, and no methods have been developed to assess how these errors affect machining accuracy in such machines.
Innovation Solution
A method involving positioning a reference sphere aligned with the tool spindle, using a position measuring device to acquire displacement data, and identifying geometric errors through a least squares method with a mathematical expression that accounts for rotation angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ball bar measurement or R-test measurement is used to evaluate geometric errors, then measurement precision is improved, but the method becomes inapplicable to machine tools with limited movable ranges
Solution Approach 1:
The patent changes the measurement parameters by using a reference sphere positioned at the rotation centerline instead of offset positions, and measures displacement along the rotation centerline rather than radial displacement. This allows geometric error evaluation within the limited movable range of spindle-moving lathes while maintaining measurement precision.
2Difficulty of detecting and measuring
If a reference sphere is positioned offset from the rotation centerline to measure geometric errors, then geometric error detection capability is improved, but the reference sphere moves significantly with rotation causing measurement instability
Solution Approach 1:
The patent positions the reference sphere at the rotation centerline of the workpiece, creating an equipotential position where the sphere remains stationary during rotation. This eliminates the significant movement that occurs when the reference sphere is positioned offset from the centerline, ensuring measurement stability while maintaining geometric error detection capability.
3Measurement precision
If multiple measurement steps with different positions and angles are performed to identify geometric errors, then measurement completeness is improved, but measurement time and complexity increase
Solution Approach 1:
The patent creates a universal measurement method that can identify multiple types of geometric errors (rotation axis position errors, swivel axis position errors, and angular errors) through a single measurement configuration. By positioning the reference sphere at the rotation centerline and using displacement measurement along this centerline, the method achieves comprehensive geometric error identification without requiring multiple separate measurement steps.
Data Source
AI summary
A method for identifying geometric errors in a machine tool includes the steps of: positioning a reference sphere so as to align its center with a centerline of a tool spindle; attaching a position measuring device having a gauge head to a rotation unit so as to direct the gauge head toward a rotation centerline of the rotation unit; acquiring displacement data relative to the center of the reference sphere by measuring positions of the reference sphere with the gauge head while rotating a rotation target (the swivel unit or the rotation unit) with the gauge head directed toward the center of the reference sphere, the displacement data being dependent on rotation angles of the rotation target; and identifying the geometric errors by least squares method using a mathematical expression having terms containing the geometric errors and representing displacement dependent on the rotation angles, and the displacement data.