Fluctuation prediction of machining accuracy for multi-axis machine tool based on stochastic process theory

2014 ◽  
Vol 229 (14) ◽  
pp. 2534-2550 ◽  
Author(s):  
Qiang Cheng ◽  
Qiunan Feng ◽  
Zhifeng Liu ◽  
Peihua Gu ◽  
Ligang Cai
Keyword(s):  
Stochastic Process ◽  
Machine Tool ◽  
Significant Influence ◽  
Geometric Error ◽  
Error Modeling ◽  
Precision Machining ◽  
Machining Accuracy ◽  
Geometric Errors ◽  
Volumetric Error ◽  
Ultra Precision

Geometric error has significant influence on the processing results and reduces machining accuracy. Machine tool geometric errors can be interpreted as a deterministic value with an uncertain fluctuation of probabilistic distribution. Although, the uncertain fluctuation can not be compensated, it has extremely profound significance on the precision and ultra-precision machining to reduce the fluctuation range of machining accuracy as far as possible. In this paper, a typical 3-axis machine tool with high precision is selected and the fluctuations in machining accuracy are studied. The volumetric error modeling of machine tool is established by multi-body system (MBS) theory, which describes the topological structure of MBS in a simple and convenient matrix form. Based on the volumetric error model, the equivalent components of the errors for the three axes are established by reducing error terms. Then, the fluctuations of equivalent errors and the machining accuracy in working planes are depicted and predicted using the theory of stochastic process, whose range should be controlled within a certain confidence interval. Furthermore, the critical geometric errors that have significant influence on the machining accuracy fluctuation are identified. Based on the analysis results, some improvement in the machine tool parts introduced and the results for the modified machine show that the prediction allow for reduction in errors for the precision and ultra-precision machining.

scholarly journals An Analysis Methodology for Stochastic Characteristic of Volumetric Error in Multiaxis CNC Machine Tool

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Qiang Cheng ◽  
Can Wu ◽  
Peihua Gu ◽  
Wenfen Chang ◽  
Dongsheng Xuan
Keyword(s):  
Machine Tool ◽  
Geometric Error ◽  
Error Modeling ◽  
Machining Accuracy ◽  
Geometric Errors ◽  
Cnc Machine ◽  
Analysis Model ◽  
Volumetric Error ◽  
Value Analysis ◽  
Stochastic Characteristic

Traditional approaches about error modeling and analysis of machine tool few consider the probability characteristics of the geometric error and volumetric error systematically. However, the individual geometric error measured at different points is variational and stochastic, and therefore the resultant volumetric error is aslo stochastic and uncertain. In order to address the stochastic characteristic of the volumetric error for multiaxis machine tool, a new probability analysis mathematical model of volumetric error is proposed in this paper. According to multibody system theory, a mean value analysis model for volumetric error is established with consideration of geometric errors. The probability characteristics of geometric errors are obtained by statistical analysis to the measured sample data. Based on probability statistics and stochastic process theory, the variance analysis model of volumetric error is established in matrix, which can avoid the complex mathematics operations during the direct differential. A four-axis horizontal machining center is selected as an illustration example. The analysis results can reveal the stochastic characteristic of volumetric error and are also helpful to make full use of the best workspace to reduce the random uncertainty of the volumetric error and improve the machining accuracy.

Modeling and Identification of Geometric Error Based on Screw Theory

2014 ◽  
Vol 941-944 ◽  
pp. 2219-2223 ◽  
Author(s):  
Guo Juan Zhao ◽  
Lei Zhang ◽  
Shi Jun Ji ◽  
Xin Wang
Keyword(s):  
Machine Tool ◽  
Laser Interferometer ◽  
Screw Theory ◽  
Geometric Error ◽  
New Method ◽  
Geometric Errors ◽  
Volumetric Error ◽  
B Spline ◽  
The Individual

In this paper, a new method is presented for the identification of machine tool component errors. Firstly, the Non-Uniform Rational B-spline (NURBS) is established to represent the geometric component errors. The individual geometric errors of the motion parts are measured by laser interferometer. Then, the volumetric error for a machine tool with three motion parts is modeled based on the screw theory. Finally, the simulations and experiments are conducted to confirm the validity of the proposed method.

Sensitivity Analysis of Geometric Errors for Five-Axis CNC Machine Tool Based on Multi-Body System Theory

2012 ◽  
Vol 271-272 ◽  
pp. 493-497
Author(s):  
Wei Qing Wang ◽  
Huan Qin Wu
Keyword(s):  
System Theory ◽  
Sensitivity Analysis ◽  
Machine Tool ◽  
Geometric Error ◽  
Machining Accuracy ◽  
Geometric Errors ◽  
Body System ◽  
Cnc Machine ◽  
Multi Body ◽  
Five Axis

Abstract: In order to determine that the effect of geometric error to the machining accuracy is an important premise for the error compensation, a sensitivity analysis method of geometric error is presented based on multi-body system theory in this paper. An accuracy model of five-axis machine tool is established based on multi-body system theory, and with 37 geometric errors obtained through experimental verification, key error sources affecting the machining accuracy are finally identified by sensitivity analysis. The analysis result shows that the presented method can identify the important geometric errors having large influence on volumetric error of machine tool and is of help to improve the accuracy of machine tool economically.

Geometric accuracy allocation for multi-axis CNC machine tools based on sensitivity analysis and reliability theory

2014 ◽  
Vol 229 (6) ◽  
pp. 1134-1149 ◽  
Author(s):  
Qiang Cheng ◽  
Ziling Zhang ◽  
Guojun Zhang ◽  
Peihua Gu ◽  
Ligang Cai
Keyword(s):  
Sensitivity Analysis ◽  
Machine Tool ◽  
Operating Conditions ◽  
Numerical Control ◽  
Cnc Machine Tools ◽  
Machining Accuracy ◽  
Geometric Errors ◽  
Volumetric Error ◽  
The Cost ◽  
Five Axis

Machining accuracy of a machine tool is influenced by geometric errors produced by each part and component. Different errors have varying influence on the machining accuracy of a tool. The aim of this study is to optimize errors to get a desired performance for a numerical control machine tool. Applying multi-body system theory, a volumetric error model was constructed to track and compensate effects of errors during operation of the machine, and to relate the functional specifications on volumetric accuracy to the permissible errors on the joints and links of the machine. Error sensitivity analysis was used to identify the influence of different errors (especially the errors which have large influences) on volumetric error. Based on First Order and Second Moment theory, an error allocation approach was developed to optimize allocation of manufacturing and assembly tolerances along with specifying the operating conditions to determine the optimal level of these errors so that the cost of controlling them and the cost of failure to meet the specifications is minimized. The approach developed was implemented in software and an example of the geometric errors budgeting for a five-axis machine was discussed. It is identified that the different optimal standard deviations reflect the cost-weighted influences of the respective parameters in the equations of the functional requirements. This study suggests that it is possible to determine the coupling relationships between these errors and optimize the allowable error budgeting between these sources.

To Identify Key Geometric Errors of 3-Axis NC Machine Tool by Machining Accuracy Failure Mode Analysis

2019 ◽  
Author(s):  
Baobao Qi ◽  
Qiang Cheng ◽  
Zhifeng Liu ◽  
Dongyang Sun
Keyword(s):  
Machine Tool ◽  
Failure Mode ◽  
Failure Modes ◽  
Geometric Error ◽  
Mode Analysis ◽  
Major Influence ◽  
Work Piece ◽  
Machining Accuracy ◽  
Geometric Errors ◽  
Machined Surface

Abstract Machine tools usually cut two or more surfaces after the work piece clamped on work table. In order to improve the machining accuracy and optimize accuracy design, it is hoped that the geometric errors that influence the accuracy of machined surface prominently can be known beforehand, so the adjustment will be carried out with a definite objective rather than without any clue. Because the machining accuracy of each direction in 3-D space is different value, in this paper, machining accuracy failure mode was defined as the various combination of the machining accuracy of each direction according to whether it is up to the reserved objective value or not. A three-axis machine tool was selected as an example and there were 7 machining accuracy failure modes for it. Based on the generalized correlation analysis, the correlation relationships between 7 machining accuracy failure modes were analyzed, and the main failure modes that affect the machining accuracy of work piece to be machined were identified. For each machining accuracy failure mode, key geometric error that had major influence on it was identified based on sensitivity analysis. Finally, four stepped work pieces were milled by a 3-axis machine tool to illustrate the analytical method proposed in this study.

Geometric Error Modeling of a Vertical Machining Center

2013 ◽  
Vol 694-697 ◽  
pp. 1842-1845
Author(s):  
Gui Qiang Liang ◽  
Jun Xian Zhang ◽  
Fei Fei Zhao
Keyword(s):  
Coordinate Transformation ◽  
Transformation Method ◽  
Geometric Error ◽  
Error Modeling ◽  
Machining Accuracy ◽  
Geometric Errors ◽  
Lower Body ◽  
Body System ◽  
Machining Center ◽  
Multi Body

The effect of geometric error on machining accuracy was researched by multi-body system theory, as well as homogeneous coordinate transformation method. Taking a vertical machining center as example, topological structure of the machine tool was described by lower body array. Lower body array of the machining center, motion freedom between adjacent bodies and geometric errors of the vertical machining center were analyzed. Geometric errors of the bodies in the multi-body system were expressed by homogeneous coordinate transformation. Error model for machining accuracy was deduced and geometric errors having influence on the machining accuracy were identified. The research results provide guidance for analyze of geometric errors on machining accuracy.

Geometric Errors Sensitivity Analysis of Precision Vertical Machining Center Based on Multi-Body System Theory

2011 ◽  
Vol 108 ◽  
pp. 61-66 ◽  
Author(s):  
Qiang Cheng ◽  
Dong Sheng Xuan ◽  
Jie Sun ◽  
Zhi Feng Liu
Keyword(s):  
System Theory ◽  
Sensitivity Analysis ◽  
Machine Tool ◽  
Great Influence ◽  
Geometric Error ◽  
Machining Accuracy ◽  
Geometric Errors ◽  
Body System ◽  
Machining Center ◽  
Multi Body

Parts of geometric error coupled into space error is the main reason that affects machining accuracy of machine tools; therefore, how to determine the effect of geometric error to the machining accuracy and then assigning geometry precision of parts economically is a difficult problem in machine tool designing process. Therefore, based on multi-body system theory, a sensitivity analysis method of geometric error is put forward in this paper. Let’s take precision vertical machining center for an example. Firstly, an accuracy model of machining center is established based on multi-body system theory, and with 21 geometric errors obtained through experimental verification, key error sources affecting the machining accuracy are finally identified by sensitivity analysis. The example analysis shows that the proposed method can effectively identify the main geometric errors of parts that have great influence on volumetric error of machine tool, and thus provides important theoretical basis to improve the accuracy of machine tool economically.

scholarly journals A Recognition Methodology for the Key Geometric Errors of a Multi-Axis Machine Tool Based on Accuracy Retentivity Analysis

Complexity ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-21
Author(s):  
Shijie Guo ◽  
Shufeng Tang ◽  
Dongsheng Zhang
Keyword(s):  
Machine Tool ◽  
Screw Theory ◽  
Operation Time ◽  
Geometric Error ◽  
Machining Accuracy ◽  
Fruit Fly Optimization Algorithm ◽  
Geometric Errors ◽  
Spatial Error ◽  
Feature Extraction Method ◽  
Fruit Fly Optimization

This paper proposes a recognition methodology for key geometric errors using the feature extraction method and accuracy retentivity analysis and presents the approach of optimization compensation of the geometric error of a multiaxis machine tool. The universal kinematics relations of the multiaxis machine tool are first modelled mathematically based on screw theory. Then, the retentivity of geometric accuracy with respect to the geometric error is defined based on the mapping between the constitutive geometric errors and the time domain. The results show that the variation in the spatial error vector is nonlinear while considering the operation time of the machine tool and the position of the motion axes. Based on this aspect, key factors are extracted that simultaneously consider the correlation, similarity, and sensitivity of the geometric error terms, and the results reveal that the effect of the position-independent geometric errors (PIGEs) on the error vectors of the position and orientation is greater than that of the position-dependent geometric errors (PDGEs) of the linear and rotary axes. Then, the fruit fly optimization algorithm (FOA) is adopted to determine the compensation values through multiobjective tradeoffs between accuracy retentivity and fluctuation in the geometric errors. Finally, an experiment on a four-axis horizontal boring machine tool is used to validate the effectiveness of the proposed approach. The experimental results show that the variations in the precision of each test piece are lower than 25.0%, and the maximum variance in the detection indexes between the finished test pieces is 0.002 mm when the optimized parameters are used for error compensation. This method not only recognizes the key geometric errors but also compensates for the geometric error of the machine tool based on the accuracy retentivity analysis results. The results show that the proposed methodology can effectively enhance the machining accuracy.

Research on Volumetric Error Measurement, Modeling and Compensation for NC Machine Tools

2014 ◽  
Vol 513-517 ◽  
pp. 4202-4205
Author(s):  
Hong Xin Zhang ◽  
Qian Jian Guo
Keyword(s):  
Machine Tool ◽  
Error Compensation ◽  
Machine Tools ◽  
Thermal Error ◽  
Error Modeling ◽  
Cnc Machine Tools ◽  
Machining Accuracy ◽  
Volumetric Error ◽  
The Impact ◽  
Thermal Error Compensation

With the increasing requirements of the machining accuracy of CNC machine tools, the impact of thermal deformation is growing. Thermal error compensation technology can predict and compensate the thermal errors in real-time, and improve the machining accuracy of the machine tool. In this paper, the research objects of thermal error compensation is expanded to the volumetric error of the machine tool, the volumetric error modeling of a three-axis machine tool is fulfilled and a compensator is developed for the compensation experiment, which provides scientific basis for the improvement of the machining accuracy.

Application of Ant Colony Algorithm to Volumetric Thermal Error Modeling and Compensation of a CNC Machine Tool

2012 ◽  
Vol 170-173 ◽  
pp. 3487-3490
Author(s):  
Qian Jian Guo ◽  
Qing Wen Qu ◽  
Jian Guo Yang
Keyword(s):  
Machine Tool ◽  
Error Compensation ◽  
Ant Colony Algorithm ◽  
Error Modeling ◽  
Ant Colony ◽  
Machining Accuracy ◽  
Cnc Machine Tool ◽  
Cnc Machine ◽  
Volumetric Error ◽  
Volumetric Errors

Volumetric errors are the major contributor to the dimensional errors of a workpiece in precision machining. Error compensation technique is a cost-effective way to reduce volumetric errors. Accurate modeling of volumetric errors is a prerequisite of error compensation. In this paper, a volumetric error model was proposed by using neural networks based on ant colony algorithm. Finally, a volumetric error compensation system was developed based on the proposed model, and which has been applied to a CNC machine tool in daily production. The results show that the volumetric errors are reduced and the machining accuracy of the machine tool is improved.

Sign in / Sign up

Export Citation Format

Share Document