Machine Tool Error Correction Using Segmented Axis Computation
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Solution Overview
Problem
Current methods for correcting geometric errors in five-axis machine tools are inadequate as they fail to accurately compute correction values for both positional and orientation errors, especially when the rotational axis is clamped, leading to increased load and potential overheating, and are unable to manage all errors in six-degrees-of-freedom space effectively.
Innovation Solution
A method that computes correction values for machine tools with translational and rotational axes by using geometric parameters to correct positional and orientation errors, where the rotational axis correction value is calculated independently of the rotational axis command value, and the translational axis correction value is computed using the rotational axis correction value, allowing for reduced calculation and preventing forced movement of the rotational axis during clamping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If correction values are computed using conventional methods that consider geometric errors, then positional error of tool center point is corrected, but orientation error of tool is not corrected and calculation complexity increases
Solution Approach 1:
The correction method is segmented into two distinct parts: (1) correction of tool center point positional error using command values and geometric parameters, and (2) correction of tool orientation error using rotation matrix calculations. This segmentation allows each correction aspect to be handled independently with appropriate computational complexity, avoiding the need for a single complex unified correction system.
Solution Approach 2:
The patent extracts the orientation correction component from the overall correction system and handles it separately through rotation matrix calculations. By taking out the orientation correction as a distinct function, the system avoids the computational complexity that would arise from attempting to correct both position and orientation simultaneously through a single complex calculation framework.
2Adaptability or versatility
If rotational axis correction value is computed using command values, then correction is adaptive, but calculation becomes complex and forced movement occurs when rotational axis is clamped
Solution Approach 1:
The patent computes the rotational axis correction value in advance based on geometric parameters before actual machining operations. This preliminary computation allows the correction value to be determined without relying on real-time command values, reducing calculation complexity during machining while maintaining adaptability through pre-computed correction values that account for geometric errors.
Solution Approach 2:
The patent uses a copy of the geometric parameter data to compute correction values independently of the command value system. By creating a separate correction computation pathway that copies necessary geometric information, the system avoids the complexity of integrating command value-based adaptive correction while still achieving effective error compensation.
3Manufacturing precision
If conventional correction methods are used, then positional error is corrected, but six-degrees-of-freedom errors cannot be managed effectively
Solution Approach 1:
The patent extends the correction approach from three-dimensional positional correction to six-dimensional error management by incorporating both tool center point position correction and tool orientation correction. This dimensional extension is achieved by adding rotation matrix-based orientation correction to the existing position correction framework, enabling comprehensive management of all six degrees of freedom (three positional + three orientational).
Data Source
AI summary
The present invention provides a method of computing a correction value for the machine tool having two or more translational axes and one or more rotational axes for correcting error in a position and an orientation of the tool with respect to a workpiece due to the geometric error. The method includes a rotational axis correction value computing step (S3) for computing a correction value for the rotational axis by use of a geometric parameter representing the geometric error, and a translational axis correction value computing step (S4) for computing a correction value for the translational axis by use of a command value for each of the rotational axes, a command value for each of the translational axes, and the geometric parameter.