Abstract

Sensitive geometric errors of a machine tool have significant influence on machining accuracy, and it is important to identify them. Complex modeling and analysis must be carried out to identify the sensitive geometric errors of a five-axis machine tool by using the traditional method. Once the configuration structure of the machine tools is reconstructed, repetitive error modeling and analysis are required, and the identification cycle of sensitive geometric errors is long. Therefore, this paper proposes a high-efficient calculation method for sensitive position-dependent geometric error (PDGEs) identification of a five-axis reconfigurable machine tool. According to the results of sensitive geometric errors of the RTTTR-type and TTTRR-type five-axis machine tools, the mapping expressions between sensitive PDGEs and the configuration structure of machine tools was established. In this method, sensitive PDGEs can be calculated directly according to the mapping expression, which eliminates the process of error modeling and analysis. Taking a RTTTR-type five-axis machine tool as an example, the sensitive PDGEs were calculated according to the presented mapping expressions without error modeling and analysis. A series of analysis points in the machining area were selected to compare the machining errors before and after sensitive PDGE compensation. The results show that this calculation method is accurate.

Highlights

  • Five-axis computer numeric controlled (CNC) machine tools play a leading role in the complex surface manufacturing of high-end parts, and precision is one of the key indexes to evaluate its performance

  • The proposed method can directly identify sensitive PDGEs according to the configuration structure of the machine tool without requiring theoretical modeling and sensitivity analysis, which is suitable for quick error analysis of a machine tool

  • Based on the error modeling and sensitive PDGEs analysis method described in Section 2.1, the sensitive PDGEs analyses of RTTTR and TTTRR-type five-axis reconfigurable machine tools with different structures were carried out, respectively

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Summary

Introduction

Five-axis computer numeric controlled (CNC) machine tools play a leading role in the complex surface manufacturing of high-end parts, and precision is one of the key indexes to evaluate its performance. CHENG et al established the sensitivity matrix of a four-axis precision machine tool based on the matrix differential method and used the LSA method to identify the key geometric errors of the machine tool [10]. The Morris global sensitivity analysis method, based on variable discrete and random sampling, can effectively analyze the sensitivity of the PDGEs of five-axis machine tools Both LSA and GSA are effective methods for sensitive geometric error identification, they need error modeling and analysis process based on HTM, which has a low response speed when structure is reconfigured. The proposed method can directly identify sensitive PDGEs according to the configuration structure of the machine tool without requiring theoretical modeling and sensitivity analysis, which is suitable for quick error analysis of a machine tool.

Theoretical Basis of the High-Efficient Calculation Method
Morris Global Sensitivity Analysis Method
X: X axis
Discovery of Mapping Relationships
The Defined Symbols and Expressions
Calculation Method of RTTTR-Type Five-Axis Machine Tools
Sensitive Linear PDGEs for Translational Axes
Sensitive Linear PDGEs for Rotational Axes
Sensitive Angular PDGEs of Translational Axis
Sensitive Angular PDGEs of Rotational Axis
Calculation Method of TTTRR-Type five-Axis Machine Tools
Sensitive Linear PDGEs of Translational Axis
Summary of Mapping Expressions
Findings
Simulation Analysis

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