A Small Displacement Torsor Model To Evaluate Machining Accuracy In The Presence Of Locating And Machine Geometric Errors

2021 ◽  
Author(s):  
Mondher Souilah ◽  
Antoine Tahan ◽  
Nabil Abacha
Keyword(s):  
Small Displacement ◽  
Machining Accuracy ◽  
Geometric Errors ◽  
Small Displacement Torsor

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.

An Analysis Model to Predict Rotation Accuracy of High-Precision Spindles Considering Part Errors and Deformation

2017 ◽  
Author(s):  
Yanhui Sun ◽  
Jun Hong ◽  
Junkang Guo ◽  
Yanfei Zhang ◽  
Shaoke Wan ◽  
...  
Keyword(s):  
High Precision ◽  
Design Stage ◽  
Small Displacement ◽  
Analysis Model ◽  
Transformation Matrices ◽  
Beam Elements ◽  
Fea Model ◽  
Small Displacement Torsor ◽  
Variation Propagation ◽  
Error Accumulation

High-precision spindles have significant influence on the machining precision and finishing quality largely due to their motion errors. However, the analysis of rotation accuracy is quite not easy in design stage because of the neglecting of geometric errors and deformations of parts in the traditional dimension chains. Hence, a theoretical analysis model is built in present study to do the prediction. The 3D error accumulation path is recognized by Datum Flow Chain (DFC) and the key tolerances are modeled by Small Displacement Torsor (SDT). Thereafter, the variation propagation is conducted by Homogeneous Transformation Matrices (HTM) and the geometric misalignment in the spindle is calculated. Then, an FEA model is built with Timoshenko beam elements and the deformation is calculated after the geometric misalignment is applied to the model. As spindle rotates, the trajectory of the spindle nose is obtained. Finally, the Monte Carlo (MC) method is used to get the distribution and the range of motion errors. To verify the feasibility and reliability of the analysis model, the radial and axial motion errors of a double supported high-precision spindle are analyzed.

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.

The Effect of Geometric Error on Machining Accuracy for Machining Center

2013 ◽  
Vol 690-693 ◽  
pp. 3244-3248
Author(s):  
Gui Qiang Liang ◽  
Ai Rong Zhang ◽  
Ting Ting Guo
Keyword(s):  
Great Influence ◽  
Geometric Error ◽  
Linear Displacement ◽  
Machining Accuracy ◽  
Geometric Errors ◽  
Lower Body ◽  
Body System ◽  
Research Results ◽  
Machining Center ◽  
Multi Body

In order to improve machining accuracy of machining center, the effect of geometric error on machining accuracy was researched by multi-body system theory. Taking a vertical machining center as example, topological structure of the machining center was described by lower body array. 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 great influence on the machining accuracy were identified. The research results show that, straightness errors and linear displacement errors in three directions have direct influence on machining accuracy, and the effect on machining accuracy caused by angle errors are related to the dimensions of the machining center and travel distance of the three axes. The research results provide guidance for analysis on sensitivity of geometric errors.

Semantic Representation of Flatness Based on ALC(R) and Mathematical Definition

2013 ◽  
Vol 662 ◽  
pp. 961-965
Author(s):  
Yun Feng Xie ◽  
Yu Lu Du ◽  
Yan Ru Zhong ◽  
Yu Chu Qin
Keyword(s):  
Semantic Representation ◽  
Heterogeneous Systems ◽  
Mathematical Representation ◽  
Small Displacement ◽  
3D Cad ◽  
Logical Language ◽  
Small Displacement Torsor ◽  
Tolerance Specification ◽  
Representation Language ◽  
Important Significance

The information of form tolerances in existing 3D CAD systems is just a kind of symbol and text which is lack of engineering semantic at present. Therefore, a reasonable explanation and Semantic representation of form tolerances has very important significance. In order to reduce the uncertainty and support the semantic interoperability in tolerance specification design, an approach for mathematical representation of flatness based on the Small Displacement Torsor (SDT) is proposed. Based on this, a representation of flatness using description logical language ALC(R) with concrete domain is proposed. Then flatness information is formalized using OWL, an ontology representation language devised by W3C, to be shared and interoperated between heterogeneous systems by building OWL ontology. At last, there is a practical example to verify the feasibility of this approach.

A small displacement torsor model for tolerance analysis in a workpiece-fixture assembly

2009 ◽  
Vol 223 (8) ◽  
pp. 1005-1020 ◽  
Author(s):  
J N Asante
Keyword(s):  
Effective Means ◽  
Experimental System ◽  
Tolerance Analysis ◽  
Geometric Error ◽  
Small Displacement ◽  
Small Displacement Torsor ◽  
Set Up ◽  
Workpiece Setup ◽  
Feature Constraints

Workpiece geometric error, locator geometric error, and clamping error are factors that influence workpiece setup in workpiece fixturing. These errors accumulate and propagate during fixturing. They may be the reason for a machined feature being out of tolerance after machining. This paper presents a methodology for modelling and analysing the combined effect of these errors on a machined feature. Deviation of a machined feature due to the combined errors is expressed in terms of the small displacement torsor parameters. Given a tolerance on the machined feature, constraints are specified for that feature to establish a relationship between the tolerance zone of the feature and the torsor parameters. These constraints provide boundaries within which the machined feature must lie. This is used for tolerance analysis of the machined feature. A case study example was used to illustrate the approach. An experimental system was also set up to verify the analytical model. The results show that this approach offers an effective means for fixturing tolerance analysis.

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.

scholarly journals Coupling and Decoupling Measurement Method of Complete Geometric Errors for Multi-Axis Machine Tools

2020 ◽  
Vol 10 (6) ◽  
pp. 2164
Author(s):  
Hongwei Wang ◽  
Yan Ran ◽  
Shengyong Zhang ◽  
Yulong Li
Keyword(s):  
Machine Tools ◽  
Measurement Method ◽  
Machining Accuracy ◽  
Geometric Errors ◽  
Homogeneous Transformation Matrix ◽  
Ultra Precision ◽  
Prediction And Control ◽  
Bar Test ◽  
And Control ◽  
Error Transfer

Precision and ultra-precision machining technology rely mainly on the machine tools’ accuracy. To improve it, the measurement, calculation, prediction and control of geometric errors are critical. The traditional measurement methods have lower precision because of ignoring small angle errors. To obtain complete geometric errors of multi-axis machine tools, this paper proposes a new method of coupling and decoupling measurement. Specifically, we used a laser interferometer and dial indicators to measure 36 items of complete geometric errors of multi-axis machine tools. A homogeneous transformation matrix (HTM) was applied to model the error transfer route. The transfer law of complete errors for each machining point was explored and derived. Furthermore, we selected and calculated integrated errors of 36 machining points. Finally, we proved the correctness of the method by comparing the measurement result of a ball bar test and coupling and decoupling measurement of geometric errors. We found that items of small geometric angle errors have a greater impact on machining accuracy than those of geometric displacement errors. Complete geometric errors measured via the coupling and decoupling measurement method can evaluate integrated errors more precisely and comprehensively.

Sensitivity analysis of machining accuracy reliability considering partial correlation of geometric errors for Horizontal Machining Center

2020 ◽  
pp. 095440542095884 ◽  
Author(s):  
Peng Niu ◽  
Qiang Cheng ◽  
Wenfen Chang ◽  
Xuemin Song ◽  
Yansheng Li
Keyword(s):  
Machine Tool ◽  
Partial Correlation ◽  
Correlation Coefficients ◽  
Working Time ◽  
Machining Accuracy ◽  
Geometric Errors ◽  
Analysis Method ◽  
Multibody Modeling ◽  
Modeling Technology ◽  
Machining Center

With the increase in working time, the geometric errors of a Horizontal Machining Center (HMC) will also increase under load, temperature, and wear conditions, decreasing the machining accuracy. As HMC is a high-accuracy machine tool with a high nonlinear system, there is a complex coupling relationship between errors. Therefore, how to thoroughly evaluate the ability of a machine tool to maintain its machining accuracy with the extension of working time is an important way for HMC to control its machining quality. In this paper, this ability is defined as machining accuracy reliability, that is, under specified conditions, the machine tool can work normally to achieve the corresponding machining accuracy ability. To solve this problem, a new analysis method is proposed for evaluating machining accuracy reliability based on the nonlinear correlation between errors. The nonlinear relationship between machining accuracy and errors was determined using multibody modeling technology. The effect of interaction between errors on machining accuracy reliability was analyzed by introducing and calculating partial correlation coefficients. Finally, the method was validated using a four-axis machine tool.

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