Transmission system accuracy optimum allocation for multiaxis machine tools’ scheme design

2013 ◽  
Vol 227 (12) ◽  
pp. 2762-2779 ◽  
Author(s):  
Sarina ◽  
Shuyou Zhang ◽  
Jinghua Xu
Keyword(s):  
Genetic Algorithm ◽  
Machine Tools ◽  
Transmission System ◽  
Error Model ◽  
Numerical Control ◽  
Optimum Allocation ◽  
Design Stage ◽  
Manufacturing Cost ◽  
Motion Error ◽  
Error Matrix

Transmission components are the main mechanical elements in a machine system, the accuracy level of the transmission system is one of the major sources of the machining error of multiaxis machine tools. This article investigates motion error analysis, volumetric motion error model for transmission system and the accuracy allocation method for multiaxis machine tools during the early design stage. For this purpose, a transmission system volumetric motion error model, which is based on the motion error matrix and screw theory, is derived for mapping transmission components’ error parameters to the volumetric motion errors of machine tools. The volumetric motion error matrix combines motion errors along the machine tools’ kinematic chains. Subsequently, the volumetric motion error model is expressed as a volumetric motion error twist, which is formulated from the volumetric motion error matrix. Additionally, the transmission system volumetric motion error twist model is used as design criteria for accuracy optimum allocation, with constraints on the twist magnitude and design variable limits. Then, design optimization is performed by using a multiobjective nonlinear optimization technique to minimize the manufacturing cost and volumetric motion error twist pitch. To solve this multiple objective optimum problem, this study proposes an approach integrating Lagrange multiplier and gradient descent operator with non-dominated sorting genetic algorithm-II (NSGA-II). Modified non-dominated sorting genetic algorithm-II searches for an allocation scheme Pareto optimal front. Consequently, VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) determines the best compromise solution from the Pareto set. Finally, a numerical experiment for the optimal design of a numerical control machine tool is conducted, which highlights the advantages of the proposed methodology.

Modelling and real-time compensation of cutting-force-induced error on a numerical control twin-spindle lathe

2009 ◽  
Vol 224 (4) ◽  
pp. 567-577 ◽  
Author(s):  
H Wu ◽  
H J Chen ◽  
P Meng ◽  
J G Yang
Keyword(s):  
Neural Network ◽  
Cutting Force ◽  
Real Time ◽  
Bp Neural Network ◽  
Machine Tools ◽  
Error Model ◽  
Numerical Control ◽  
Machining Process ◽  
Nc Machine ◽  
Nc Machine Tools

Cutting-force-induced errors are one of the major sources of error in numerical control (NC) machine tools. The error compensation technique is an effective way to improve the manufacturing accuracy of NC machine tools. Effective compensation relies on an accurate error model that can predict the errors exactly during the machining process. In the present paper a robust and accurate cutting-force-induced error model is built using a back-propagation (BP) neural network and a genetic algorithm (GA) for an NC twin-spindle lathe. The GA—BP neural network modelling technique not only enhances the prediction accuracy of the model but also reduces the training time of the BP neural network. A real-time compensation system of the cutting-force-induced error on the lathe is developed based on the cutting-force-induced error model. The errors were reduced by about 38 per cent after real-time compensation in a machining experiment.

Research on Geometric Error Compensating Technique of CNC P3G Grinding Machine

2012 ◽  
Vol 462 ◽  
pp. 287-294 ◽  
Author(s):  
Yi Jian ◽  
Qian Qian Li ◽  
Hong Cheng ◽  
Bin Wu Lai ◽  
Jian Fei Zhang
Keyword(s):  
Machine Tools ◽  
Geometric Error ◽  
Error Model ◽  
Error Modeling ◽  
Numerical Control ◽  
Geometric Errors ◽  
Real Time Control ◽  
Time Control ◽  
Applied Software ◽  
Grinding Machine

Kinematic accuracy is a key reason which influence workpiece's geometric error precision on traditional working process of precisely CNC（Computerized Numerical Control）P3G（polygon profile with 3 lobes） grinding machine. A systematic geometric error model has been presented for CNC P3G grinding machine， proposed multi-body system theory integrate with the structure of CNC P3G grinding machine tools, researched on the machine's space geometric errors. By means of separate geometric errors from the machine tools, build geometric mathematical error model. Then, identify 21 error parameters through method of 9 lines, analysis and calculate the total space geometric errors of the workpiece and wheel. Finally, formed a parameter-list and applied software error compensational technique ， achieved real-time control to the motions of workpiece and wheel. Experimental results shown that the geometrical error modeling technique is accurate and efficient, and the precision of CNC P3G grinding machine is highly raised 70%.

Accuracy enhancement of kinematic error model of three-axis computer numerical control machine tools

2016 ◽  
Vol 231 (11) ◽  
pp. 2021-2030 ◽  
Author(s):  
Mostafa Pezeshki ◽  
Behrooz Arezoo
Keyword(s):  
Machine Tools ◽  
Laser Interferometer ◽  
Error Model ◽  
Numerical Control ◽  
Accurate Estimation ◽  
Kinematic Error ◽  
Positioning Errors ◽  
Volumetric Errors ◽  
Kinematic Error Model ◽  
Kinematic Errors

Accurate estimation of volumetric errors is an important issue in machining operations. For this purpose, a kinematic error model is used to characterize machine tool’s related errors on its workspace. In this research, it is shown that when measuring the linear and positioning errors using a laser interferometer, part of the angular errors are converted to linear and positioning errors and their magnitudes are overestimated. These values are calculated twice in the models which use homogeneous transformation matrix since Abbe’s principle is not considered. In this article, a kinematic error model is proposed which eliminates this overestimation. This model’s methodology is based on rigid body kinematic and errors measurement by laser interferometer and can be generalized for all three-axis machine tools. A software package is developed to integrate the kinematic errors with the NC-codes. A workpiece is machined in the virtual environment and compared with a workpiece machined in real environment. It is shown that the kinematic error model developed in this research predicts the kinematic errors more accurately.

Emulating and Modeling for Position Errors of Ultra-Precision Aspherical Grinding

2007 ◽  
Vol 10-12 ◽  
pp. 291-296
Author(s):  
Dong Ju Chen ◽  
Yong Zhang ◽  
Fei Hu Zhang ◽  
H.M. Wang
Keyword(s):  
Neural Network ◽  
Genetic Algorithm ◽  
Motor Coordination ◽  
Error Model ◽  
Position Error ◽  
Numerical Control ◽  
Training Data ◽  
Position Errors ◽  
The Neural Network ◽  
Ultra Precision

In the process of the ultra-precision grinding, the machining path of the aspherical is the result of motor coordination by several axes for the numerical control system. Since the motion of each axis have errors, there are big errors between the real positions and the theoretical positions, and the position error of the wheel infects the accuracy of the workpiece greatly. This paper analyses the position error property of the wheel and finds the machining approach path has nothing to do with the position error, just do with to the present machining point. In order to solve the problem, the method using the Neural Network optimized by the Genetic Algorithm to establish the position error model is introduced. A three-layer error back propagation (simplified as BP) Neural Network is used to establish the position error model, the position coordinates (x, z) of the program instruction is input layer, and the corroding measured error value ( Δx , Δz ) is output layer. Before training data sample, using the Genetic Algorithm to optimize the Neural Network to improve the predicting accuracy of the Neural Network, and reduce the training time. The emulation results indicate that using the Neural Network model optimized by the Genetic Algorithm can predict the position error in a high degree of accuracy, and at the same time, according to the predicting results, compensating the position error of the wheel is possible.

scholarly journals Performances and Shapes of Acceleration-deceleration Curve of Kinematical Linkages

2020 ◽  
Vol 14 ◽  
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Mobile Element ◽  
Industrial Robots ◽  
Numerical Control ◽  
Design Stage ◽  
Contour Error ◽  
Maximum Acceleration ◽  
Positioning Accuracy ◽  
Acceleration And Deceleration

The transient duty has a very important role within the kinematical linkages of the numerical control machine tools and industrial robots. The acceleration and deceleration of the movable element of the kinematical linkage participates directly to achieving the positioning accuracy and to the path error. This work presents the main shapes of the acceleration- deceleration curve of the kinematical linkage, as well as their performances. Shapes of the acceleration-deceleration curve are presented for positioning linkages as well as for contouring linkages. The extent of influence upon the contour error in case of the linear and exponential acceleration-deceleration of kinematical linkage is also presented. The works is also giving recommendations on the way of choosing the type of curve being used in case of various transient processes, by the machine tool builders, with a view to obtaining high dynamical performances. In general, the recommendations are considering the inertia of the mobile element and the imposed path error. By knowing the acceleration shape, the machine tool designer and builder can know, even from the design stage, the area of the transient duty where the acceleration is maximal. The maximum acceleration imposes the rate of the impulsion torque of the drive servomotor based on which the kinematical linkage is sized, in terms of its components.

Measurement Method for Measuring Circular Motion Error of CNC Machine Tools

2008 ◽  
Vol 381-382 ◽  
pp. 145-148
Author(s):  
K.H. Lin ◽  
Ya Hui Hu ◽  
C.A. Chan ◽  
Ming Chang
Keyword(s):  
Measurement System ◽  
Machine Tools ◽  
Measurement Method ◽  
Circular Motion ◽  
Numerical Control ◽  
Cnc Machine Tools ◽  
Small Scale ◽  
Large Radius ◽  
Cnc Machine ◽  
Motion Error

The dynamic characteristic of CNC (computer numerical control) machine tools is a critical role to decide the accuracy and speed of machine. It is very important to improve the precision and reduce the motion error so as to manufacture complex and fine products. In general, the motion error is estimated by a two or three-dimensional ball bar measurement system. Although this technology is capable of dynamical measurement, its condition should be confined to a low speed or a large radius. A new measurement method for measuring circular motion error of CNC machine tools is proposed in this paper. The instrument consists of a dual-frequency laser interferometer, a beam splitter and two corner cubes. In order to evaluate the exactness of the results we get from our measurement system, we use RSF’s grid encoder to do another experiment and compare both the results. According to the results shown, our measurement system can measure both of the X and Y axes of the plane of the CNC stage in a small scale at the same time and can simplify the calibration procedure as well as shorten the time of measurement. This method can accomplish the two-axis measurement at a high speed, without being restricted by radius variations. It is a good, simple and effective measurement method.

scholarly journals Study of Machining of Gears with Regular and Modified Outline Using CNC Machine Tools

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2913
Author(s):  
Rafał Gołębski ◽  
Piotr Boral
Keyword(s):  
Machine Tools ◽  
Coordinate Measuring Machine ◽  
Optical Microscope ◽  
Numerical Control ◽  
Cnc Machine Tools ◽  
Cnc Milling ◽  
Cnc Machine ◽  
Cylindrical Gears ◽  
Measuring Machine ◽  
Five Axis

Classic methods of machining cylindrical gears, such as hobbing or circumferential chiseling, require the use of expensive special machine tools and dedicated tools, which makes production unprofitable, especially in small and medium series. Today, special attention is paid to the technology of making gears using universal CNC (computer numerical control) machine tools with standard cheap tools. On the basis of the presented mathematical model, a software was developed to generate a code that controls a machine tool for machining cylindrical gears with straight and modified tooth line using the multipass method. Made of steel 16MnCr5, gear wheels with a straight tooth line and with a longitudinally modified convex-convex tooth line were machined on a five-axis CNC milling machine DMG MORI CMX50U, using solid carbide milling cutters (cylindrical and ball end) for processing. The manufactured gears were inspected on a ZEISS coordinate measuring machine, using the software Gear Pro Involute. The conformity of the outline, the tooth line, and the gear pitch were assessed. The side surfaces of the teeth after machining according to the planned strategy were also assessed; the tests were carried out using the optical microscope Alicona Infinite Focus G5 and the contact profilographometer Taylor Hobson, Talysurf 120. The presented method is able to provide a very good quality of machined gears in relation to competing methods. The great advantage of this method is the use of a tool that is not geometrically related to the shape of the machined gear profile, which allows the production of cylindrical gears with a tooth and profile line other than the standard.

Multi-objective optimization of a recuperative gas turbine cycle using non-dominated sorting genetic algorithm

2011 ◽  
Vol 225 (8) ◽  
pp. 1041-1051 ◽  
Author(s):  
H Sayyaadi ◽  
H R Aminian
Keyword(s):  
Genetic Algorithm ◽  
Gas Turbine ◽  
Heat Exchangers ◽  
Mixed Integer ◽  
Design Stage ◽  
Tube Length ◽  
Pareto Optimal ◽  
Multi Objective Optimization ◽  
Multi Objective ◽  
Gas Turbine Cycle

A regenerative gas turbine cycle with two particular tubular recuperative heat exchangers in parallel is considered for multi-objective optimization. It is assumed that tubular recuperative heat exchangers and its corresponding gas cycle are in design stage simultaneously. Three objective functions including the purchased equipment cost of recuperators, the unit cost rate of the generated power, and the exergetic efficiency of the gas cycle are considered simultaneously. Geometric specifications of the recuperator including tube length, tube outside/inside diameters, tube pitch, inside shell diameter, outer and inner tube limits of the tube bundle and the total number of disc and doughnut baffles, and main operating parameters of the gas cycle including the compressor pressure ratio, exhaust temperature of the combustion chamber and the air mass flowrate are considered as decision variables. Combination of these objectives anddecision variables with suitable engineering and physical constraints (including NO x and CO emission limitations) comprises a set of mixed integer non-linear problems. Optimization programming in MATLAB is performed using one of the most powerful and robust multi-objective optimization algorithms, namely non-dominated sorting genetic algorithm. This approach is applied to find a set of Pareto optimal solutions. Pareto optimal frontier is obtained, and a final optimal solution is selected in a decision-making process.

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