Papers by Keyword: Error Compensation

Abstract: The leaf blade manufacture precision's influencing factors are numerous, and they have coupling relationship each other. So it is difficult to peel out a single factor on the influencing regularity of the blade's machining accuracy. By researching the engine blades of helical milling state under the existing fixture, the leaf blade deformable model based on the instantaneous milling strength was established. Meanwhile, the off-line multi-level error compensation plan was proposed based on the processing surface static error forecasts and compensation. In order to revise the primitive NC tool path code and eliminate the processing distortion inaccuracy, the elastic deformity on each knife position spot is solved on the basis of iterative solution, using the finite element simulation and milling strength model. By using ANSYS finite element simulation, it receives the real-time error compensation of the tool path. And then The experiment has proven the accuracy and the usability of the compensation plan.

Abstract: With the wide use of NC, higher accuracy in machining is increasingly required for premium mechanical components. However, machining accuracy is affected by many factors, especially by the way of the tool positioning and the geometry of the tool nose. This paper, based on the actual NC lathe tool and turning, generalized and abstracted the machining process by establishing the imaginary tool nose and the tool tip’s arc centre as the cutter-contact point, and analyzed systematically the influence of the factors, including the way of the tool positioning, the nose, and the tool tip’s arc radius, on the machining accuracy when machining transverse, cylindrical-surface, circular cone, quarter-circular and some surfaces can be expressed by formula etc.. Derived the error calculating formulas for turning in different surfaces. Put forward two error compensation methods, direct calculating method and enveloping method of error compensation. Experiments were carried out and results have shown that the two error compensation methods can considerably reduce the machining error in NC turning operations.

Abstract: With the rapid development of opto-electronics communications, optics, aerospace and other industries, ultra-precision aspheric glass lenses are widely used in middle/high-grade optical opponent because of its high resolution and imaging quality. To achieve ultra-precision molding pressing of micro-lens, ultra-precision mold must be fabricated firstly. In this paper, some key new technologies were proposed for fabricating ultra-precision mold of small-size aspheric optical lens. A method of finite element simulation was employed to predict mould pressing process of the glass lens for correcting molds and improving the formation efficiency. An ultra-precision inclined-axis grinding and error compensation technology was also used to improve form accuracy of micro lens mold.

Abstract: A computational model for position and posture error of 6-DOF parallel machines is proposed based on D-H transformation matrix and the inverse kinematics. The model is used to construct a linear least-square identification model for geometric parameter errors. Error identification program and compensation method are also presented. Simulation results indicate that the effects on position and posture of machines are almost equivalent from calculated least-square solution and from real values. The pose error of moving platform can be decreased up to 90% if error compensation is performed by modifying the input kinematic parameters of driving joints.

Abstract: One of the difficult issues in thermal error modeling is to select appropriate temperature variables. In this paper, two selection strategies are introduced to overcome this difficulty. After measuring the temperatures and thermal errors of a heavy-duty CNC milling-boring machine tool by a laser tracker, four temperature variables which are the foundation of thermal error modeling are selected for each feed axis from fifteen temperature variables according to major factor strategy and non-interrelated strategy.

Abstract: The purpose of this research is to fulfill thermal error modeling and compensation of an INDEX-G200 turning center. This paper presents the whole process of thermal error modeling and compensation by using back propagation neural networks. Results show that the BP model improves the prediction accuracy of thermal errors on the turning center and the thermal drift has been reduced from 39 to 11 after compensation.

Abstract: This research presents a design of a thermal deformation errors compensation system for CNC machine tools which can compensate thermal deformation of Z-axis during the working time. The thermal deformation errors compensation system includes three instruments: displacement tester, temperature tester and thermal errors compensator. Displacement and temperature testers have been designed in the early researches, and the thermal errors compensator is designed in this research. The compensation process includes two parts, modeling part and compensation part. Modeling part focuses on making a model of thermal deformation, and compensation part focuses on using the model to compensate the thermal deformation of Z-axis during the working time.

Abstract: To improve the accuracy of the on-line inspection system used by a large-scale turning-milling machining center, its error sources were analyzed and some calibration methods were researched, including error calibration in Z, Y, -X and any angular directions. The error compensation method based on embedded HMI control and CNC variables control was proposed. The EN86N touch system with TT25G probe of Marposs is calibrated on the five-axis turning-milling machining center HTM125. The experiments improved that the calibration methods and the compensation method are reasonable and effective.

Abstract: The neural network (NN) is extensively used for error predication and compensation in CNC machining. However, the training samples are finite and have some noises which limit the training accuracy of the neural network. Furthermore, the weight matrixes and the valve values of the NN are fixed which limit the generalization performance of the trained NN. To solve the problems, some optimization techniques are proposed in this paper. A standardized formula is proposed to standardize the training samples. The data filter is designed to eliminate the noise. A correction strategy is proposed to realize the generalization performance of the trained NN.

Abstract: Thermal 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 thermal errors. Accurate modeling of errors is a prerequisite of error compensation. In this paper, a thermal error model was proposed by using projection pursuit regression (PPR). The PPR method improves the prediction accuracy of thermal deformation in the CNC turning center.