A reconfigurable mechanism model for error identification in the double ball bar tests of machine tools

2021 ◽  
pp. 103737
Author(s):  
Zhi Wang ◽  
Delun Wang ◽  
Shudong Yu ◽  
Xiaopeng Li ◽  
Huimin Dong
Keyword(s):  
Machine Tools ◽  
Error Identification ◽  
Mechanism Model ◽  
Double Ball Bar ◽  
Ball Bar

scholarly journals A novel geometric error identification methodology for the tilting head of five-axis machine tools based on double ball bar

2018 ◽  
Vol 221 ◽  
pp. 04001
Author(s):  
Jinwei Fan ◽  
Changjun Wu ◽  
Zhongsheng Li
Keyword(s):  
Machine Tools ◽  
Relative Displacement ◽  
Geometric Error ◽  
Body System ◽  
Error Identification ◽  
Double Ball Bar ◽  
Motion Condition ◽  
Ball Bar ◽  
Multi Body ◽  
Five Axis

The paper proposes a novel geometric error identification methodology for the tilting head of five-axis machine tools using double ball bar(DBB).Firstly, based on the motion condition of the tilting head of five-axis machine tools, three measurement patterns in Y direction, X direction and Z direction are proposed respectively. Then, the relative displacement equations of two balls of DBB in three measurement patterns are established respectively on the basis of homogeneous transform matrix (HTM) and multi-body system (MBS) theory. Finally, the geometric error parameters of the tilting head are identified totally. The presented method is universal and provides a reference for the error identification for the tilting head of five-axis machine tools.

A Complete, Continuous, and Minimal Product of Exponentials-Based Model for Five-Axis Machine Tools Calibration With a Single Laser Tracker, an R-Test, or a Double Ball-Bar

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Peng Xu ◽  
Benny C. F. Cheung ◽  
Bing Li
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Rigid Bodies ◽  
Error Model ◽  
Laser Tracker ◽  
Calibration Model ◽  
Transformation Matrices ◽  
Double Ball Bar ◽  
Ball Bar ◽  
Five Axis

Calibration is an important way to improve and guarantee the accuracy of machine tools. This paper presents a systematic approach for position independent geometric errors (PIGEs) calibration of five-axis machine tools based on the product of exponentials (POE) formula. Instead of using 4 × 4 homogeneous transformation matrices (HTMs), it establishes the error model by transforming the 6 × 1 error vectors of rigid bodies between different frames resorting to 6 × 6 adjoint transformation matrices. A stable and efficient error model for the iterative identification of PIGEs should satisfy the requirements of completeness, continuity, and minimality. Since the POE-based error models for five-axis machine tools calibration are naturally complete and continuous, the key issue is to ensure the minimality by eliminating the redundant parameters. Three kinds of redundant parameters, which are caused by joint symmetry information, tool-workpiece metrology, and incomplete measuring data, are illustrated and explained in a geometrically intuitive way. Hence, a straightforward process is presented to select the complete and minimal set of PIGEs for five-axis machine tools. Based on the established unified and compact error Jacobian matrices, observability analyses which quantitatively describe the identification efficiency are conducted and compared for different kinds of tool tip deviations obtained from several commonly used measuring devices, including the laser tracker, R-test, and double ball-bar. Simulations are conducted on a five-axis machine tool to illustrate the application of the calibration model. The effectiveness of the model is also verified by experiments on a five-axis machine tool by using a double ball-bar.

Accuracy evaluation of rotary axes of five-axis machine tools with a single setup of a double ball bar

2016 ◽  
Vol 231 (3) ◽  
pp. 427-436 ◽  
Author(s):  
Xiaogeng Jiang ◽  
Robert J Cripps
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Dynamic Performance ◽  
Second Step ◽  
Accuracy Evaluation ◽  
Rotary Axes ◽  
Double Ball Bar ◽  
Ball Bar ◽  
Five Axis ◽  
Rotary Type

A double ball bar (DBB) is used extensively to evaluate the geometric and dynamic performance of three-axis machine tools by means of the XY, YZ and XZ planar circular tests. However, research using a DBB to test the rotary axes of five-axis machine tools simply, quickly and effectively is scarce. In this paper, a method having two steps to identify the imprecision of the rotary axes caused by the position-independent geometric errors (PIGEs) is presented for a tilting rotary type five-axis machine tool using a DBB. The first step is designed to evaluate two rotary axes with one setup. Its advantage of fast diagnosis effectively reduces the machine down time, and thus can be employed as a quick testing approach of the machine tool. However, if some of the diagnosed errors fall outside their tolerances, a more accurate but slower check needs to be carried out due to the limitation of the first step. The second step aims to test the two rotary axes separately, each in two sub-steps. By means of varying the position of the pivot, the A- and C-axes can be tested individually. Both steps are performed with only one axis moving, thus simplifying the error analysis. Implementation of the proposed methods was carried out on a Hermle C600U five-axis machine tool. To show the validity of the method, the identified PIGEs are compensated for in each step, which suggests that the first step can be used as a fast and preliminary indication of a five-axis machine tool’s performance, whilst the second can be carried out if a more thorough evaluation is needed.

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