scholarly journals An Online Simultaneous Measurement of the Dual-Axis Straightness Error for Machine Tools

2018 ◽  
Vol 8 (11) ◽  
pp. 2130 ◽  
Author(s):  
Wen-Yuh Jywe ◽  
Tung-Hsien Hsieh ◽  
Po-Yu Chen ◽  
Ming-Shi Wang
Keyword(s):  
Machine Tool ◽  
Measurement System ◽  
Simultaneous Measurement ◽  
Machine Tools ◽  
Measured Data ◽  
Error Model ◽  
Key Factor ◽  
Straightness Error ◽  
Flatness Error ◽  
Axis Straightness

Vertical straightness errors are the key factor that affects the flatness of the workpiece during vertical machining. Traditionally, the individually measured and fitted vertical straightness errors of the X and Y axes are used to compensate the Z axis and, thus, obtain the flatness of the working table of the machine tool. However, it is difficult to measure and compensate the vertical straightness error of the desired position on the working table, not to mention the centroid variation effect of the working table on the measured data. In this study, an online dual-axis measurement system with repeatability (3σ) of 2.46 μm is developed to simultaneously measure X-axis and Y-axis straightness errors of the desired position of a working table. Furthermore, the measured data are utilized to establish a flatness error model to reduce the vertical straightness error of the working table such that the repeatability (3σ) of the measured flatness may be kept within a range of 0.65 μm.

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.

Characterization of Kinematic Error Model Consistency for Five-Axis Machine Tools

2018 ◽  
Author(s):  
Le Ma ◽  
Douglas A. Bristow ◽  
Robert G. Landers
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Error Model ◽  
Data Sets ◽  
Kinematic Error ◽  
Interior Space ◽  
Error Models ◽  
Wide Range ◽  
Kinematic Error Model ◽  
Five Axis

New metrology tools, such as laser trackers, are enabling the rapid collection of machine tool geometric error over a wide range of the workspace. Error models fit to this data are used to compensate for high-order geometric errors that were previously challenging to obtain due to limited data sets. However, model fitting accuracy can suffer near the edges of the measurable space where obstacles and interference of the metrology equipment can make it difficult to collect dense data sets. In some instances, for example when obstacles are permanent fixtures, these locations are difficult to measure but critically important for machining, and thus models need to be accurate at these locations. In this paper, a method is proposed to evaluate the model accuracy for five-axis machine tools at measurement boundaries by characterizing the statistical consistency of the model fit over the workspace. Using a representative machine tool compensation method, the modeled Jacobian matrix is derived and used for characterization. By constructing and characterizing different polynomial order error models, it is observed that the function behavior at the boundary and in the unmeasured space is inconsistent with the function behavior in the interior space, and that the inconsistency increases as the polynomial order increases. Also, the further the model is extrapolated into unmeasured space, the more inconsistent the kinematic error model behaves.

scholarly journals A new measurement system to determine stiffness distribution in machine tool workspace

2021 ◽  
Vol 21 (2) ◽  
Author(s):  
Piotr Pawełko ◽  
Daniel Jastrzębski ◽  
Arkadiusz Parus ◽  
Joanna Jastrzębska
Keyword(s):  
Signal Processing ◽  
Machine Tool ◽  
Measurement System ◽  
Machine Tools ◽  
Static Stiffness ◽  
Stiffness Coefficients ◽  
Innovative System ◽  
Working Principle ◽  
Determination Methods ◽  
Stiffness Distribution

AbstractThis paper presents an innovative system determining machine tool quasi-static stiffness in machining space, so-called Stiffness Workspace System (SWS). The system allows for the assessment of the accuracy of a machine which has become a vital aspect over past years for machine tool manufacturers and users. Since machine tools static stiffness is one of the main criteria using to evaluate the machines' quality, it is crucial to highlight the relevance of experimental and analytical stiffness determination methods. Therefore, the proposed method is applied to estimate the spatial variation of static stiffness in the machine tool workspace. This paper describes the SWS system—its design, working principle, mounting conditions and signal processing. The major advantage of the system is the capability to apply forces of controlled magnitude and orientation as well as simultaneously measure the resulting displacements. The obtained results give possibility to estimate and evaluate static stiffness coefficients depending on the position and direction under loaded conditions. The results confirm the validity of the analyses of spatial stiffness distribution in the machine workspace.

scholarly journals Identification, development and testing of thermal error compensation model for a headstock assembly of CNC turning centre

2014 ◽  
Vol 3 (2) ◽  
pp. 113 ◽  
Author(s):  
Ramesh Babu ◽  
V.Prabhu Raja ◽  
J. Kanchana ◽  
Devara Venkata Krishna
Keyword(s):  
Machine Tool ◽  
Analysis Of Variance ◽  
Error Compensation ◽  
Machine Tools ◽  
Thermal Error ◽  
Error Model ◽  
Transient Temperature ◽  
Cnc Machine ◽  
Grey Correlation ◽  
Thermal Error Model

In CNC machine tools, transient temperature variation in the headstock assembly is the major contributors for spindle thermal error. The compensation of thermal error is critical for ensuring the accuracy of machine tool. The performance of an error compensation system depends largely on the accuracy and robustness of the thermal error model. In the present work, a robust thermal error model is developed for minimizing the error in lateral direction of the spindle which significantly influences the geometrical accuracy of the workpiece. Analysis-of-variance (ANOVA) is applied to the results of the experiments in determining the percentage contribution of each individual temperature key point against a stated level of confidence. Based on the analysis of existing approaches for thermal error modeling of machine tools, an approach of LASSO (least absolute shrinkage and selection operator) is proposed in order to avoid the multi collinearity problem. The proposed method is an innovative variable selection method to remove redundant or unimportant temperature key points in the linear thermal error model and minimize the residual sum of squares. The predictive error model is found to have better robustness and accuracy in comparison to the combination of grey correlation and step wise linear regression for error compensation of CNC lathe. Keywords: Analysis Of Variance (ANOVA), CNC Machine Tool, Grey Correlation Analysis (GCA), Headstock Assembly, LASSO Regression, Mean Absolute Deviation (MAD), Mean Square Error (MSE), Robustness, Standard Deviation (SD), Thermal Error.

scholarly journals Design of a Multi-Point Kinematic Coupling for a High Precision Telescopic Simultaneous Measurement System

Sensors ◽  
2021 ◽  
Vol 21 (19) ◽  
pp. 6365
Author(s):  
Raquel Acero ◽  
Juan José Aguilar ◽  
Francisco Javier Brosed ◽  
Jorge Santolaria ◽  
Sergio Aguado ◽  
...  
Keyword(s):  
Machine Tool ◽  
High Precision ◽  
Measurement System ◽  
Process Simulation ◽  
Machine Tools ◽  
Point Contact ◽  
Simultaneous Operation ◽  
Rotary Axes ◽  
Kinematic Coupling ◽  
Verification Process

This paper covers the design of a new multi-point kinematic coupling specially developed for a high precision multi-telescopic arm measurement system for the volumetric verification of machine tools with linear and/or rotary axes. The multipoint kinematic coupling allows the simultaneous operation of the three telescopic arms that are registered at the same time to a sphere fixed on the machine tool spindle nose. Every coupling provides an accurate multi-point contact to the sphere, avoiding collisions and interferences with the other two multi-point kinematic couplings, and generating repulsion forces among them to ensure the coupling’s fingers interlacing along the machine tool x/y/z travels in the verification process. Simulation presents minimal deformation of the kinematic coupling under load, assuring the precision of the sphere-to-sphere distance measurement. Experimental results are provided to show that the multi-point kinematic coupling developed has repeatability values below ±1.2 µm in the application.

scholarly journals Modeling Method of CNC Machine Tools’ Volume Error Considering Abbe Error

2021 ◽  
Author(s):  
GUOHUA CHEN ◽  
Lin Zhang ◽  
XIANGJIE WANG ◽  
CHAO WANG ◽  
HUA XIANG ◽  
...  
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Error Model ◽  
Modeling Method ◽  
Machining Accuracy ◽  
Spatial Error Model ◽  
Spatial Error ◽  
Precision Machine ◽  
Precision Machine Tools ◽  
Abbe Error

Abstract Abbe error is an important factor affecting high-precision machine tools, and the traditional modeling method does not consider Abbe error. Aiming at this problem, based on the traditional error model of machine tools and the formation mechanism of Abbe error, this paper establishes a machine tool spatial error model that considers Abbe error. Then combined with a specific machine tool, based on the measurement of 21 geometric errors of the machine tool to obtain relevant error data, through the combination of qualitative and quantitative accuracy evaluation methods, two models of traditional error model and error model considering Abbe error are analyzed. The accuracy of the machine tool is compared, and the comparison of the compensation effects of the two error models after compensation is also analyzed. The example verification shows that the machine tool spatial error model considering Abbe error is effective and feasible, and the compensation effect is better. It provides an important modeling method for improving the machining accuracy of precision machine tools.

Development of Measurement for Motion Accuracy of 5 Axis NC Machine Tool

2008 ◽  
Vol 2 (2) ◽  
pp. 111-118 ◽  
Author(s):  
Tomoyuki Saiki ◽  
◽  
Masaomi Tsutsumi ◽  
Hiroshi Suzuki ◽  
Masahide Kouya ◽  
...  
Keyword(s):  
Machine Tool ◽  
Measurement System ◽  
Machine Tools ◽  
Circular Motion ◽  
Work Piece ◽  
Accuracy Measurement ◽  
Nc Machine Tool ◽  
Nc Machine ◽  
Tool Motion ◽  
Five Axis

In terms of the realization for high accurate and effective machining of complicated shape having under cut shape and free formed surface, five axis controlled machine tools become indispensable because they have any tool position and attitude to avoid the collision between machine tool elements and work piece. In order to estimate the motion accuracy of NC machine tool, various kinds of certificate methods like circular cone cutting test prescribed with NAS and DBB method using the circular motion have been developed and standardized. These methods are mainly used for the motion testing of three-axis NC machine tools and therefore new method and measuring equipment for five-axis NC machine tool is needed. This study aims at developing the motion accuracy measurement system which can measure various kinds of motions like linier motion, circular motion and continuous curved motion under simultaneous five-axis controlling and establishing the compensate method of tool motion. Consideration is added from the viewpoint of motion accuracy using measurement system developed in this report in case simultaneous five-axis control motion command value from CL data.

Development of Measurement System on Straightness Error for Guide of Large CNC Machine Tool

2011 ◽  
Vol 4 (6) ◽  
pp. 2337-2341 ◽  
Author(s):  
Xiumin Yang ◽  
Lixia Li ◽  
Guanghua Liu ◽  
Sen Wang ◽  
Lei Zhang
Keyword(s):  
Machine Tool ◽  
Measurement System ◽  
Cnc Machine Tool ◽  
Cnc Machine ◽  
Straightness Error
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