共查询到20条相似文献,搜索用时 31 毫秒
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Achieving workpiece high accuracy at low cost is one of the greatest challenges in the manufacturing industry. A repetitive
error measurement and compensation scheme to improve the workpiece diameter accuracy for machining centres is des-cribed.
The scheme entails an on-machine measurement and error compensation technology between machining processes. The workpiece
diameters are measured along the workpiece length by using a fine touch sensor. The workpiece diameters in the compensation
program are modified for implementation of next pass error correction. The technology is realised on a CNC turning centre.
This method works well in hard machining and turned workpieces with large length–diameter ratios where the machining process
induced errors are significantly greater than errors from other sources. It demonstrates that the work-piece can obtain maximum
possible machining accuracy by this repetitive measurement and compensation technique. 相似文献
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Optimisation of workpiece setup for continuous five-axis milling: application to a five-axis BC type machining centre 总被引:1,自引:2,他引:1
Xavier Pessoles Yann Landon Stéphane Segonds Walter Rubio 《The International Journal of Advanced Manufacturing Technology》2013,65(1-4):67-79
When machining complex geometries on five-axis machining centres, the orientation and positioning of the workpiece in the machine workspace are generally chosen arbitrarily by the operator from the Computer-Aided Manufacturing software. Nevertheless, these two factors have considerable influence on the machining time. The present article firstly studies the choice of workpiece orientation. Relying on analysis of the machine’s kinematic behaviour, orientations of the workpiece in the machine workspace are proposed minimising the overall distance travelled by the rotary axes. Secondly, choice of workpiece positioning in translation is studied. To this purpose, the work volume in five-axis machining is identified so as to avoid overshooting the machine travels when the program is executed. The optimum positioning is chosen to minimise the overall distance covered by the machine’s axes of translation. Finally, the proposed method provides for a workpiece setup to be adopted that minimises the distances covered by the machine axes. This leads to reduced machining time with concomitant gains in productivity and greater respect for the cutter/workpiece relative feed rate for enhanced quality. 相似文献
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On-line Estimation of Workpiece Height by Using Neural Networks and Hierarchical Adaptive Control of WEDM 总被引:2,自引:0,他引:2
M. T. Yan Y. S. Liao C. C. Chang 《The International Journal of Advanced Manufacturing Technology》2001,18(12):884-891
Wire breakage and unstable machining drastically reduce the machining efficiency and accuracy in wire electrical discharge
machining (WEDM). When a stair-shaped workpiece is machined, poor electrolyte flow around the steps leads to wire rupture
or unstable machining. This paper presents a WEDM adaptive control system that maintains optimal machining and improves the
stability of machining at the stair section where workpiece thickness changes. A three-layer back propagation neural network
is used to estimate the thickness of a workpiece. The developed adaptive control system is executed in the hierarchical structure
of three control loops, using fuzzy control strategy. In the first control loop, the total sparking frequency is controlled
within a safe level for wire rupture suppression. In the second control loop, the proportion of abnormal sparks is maintained
at a pre-determined level for process control purposes. Based on the estimated thickness of a workpiece, adaptive parameter
optimisation is carried out to determine the optimal machining settings and to provide the reference targets for the other
two control loops. Experimental results demonstrate that the workpiece height can be estimated by using a feed-forward neural
network. The developed adaptive control system results in faster machining and better machining stability than does the commonly
used gap voltage control system. 相似文献
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数控车床加工零件时工件原点一般选择在工件右端面,但有时采用这种方案却很难实现零件的加工要求。结合一盘形端盖零件的加工,说明灵活运用工件坐标系能实现零件的高效、精确加工。 相似文献
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利用数控机床工作台的回转中心设置工件零点的技巧 总被引:1,自引:0,他引:1
工件零点是工件坐标系的原点,在加工中心上一次装夹需要设置多个工件零点。利用工作台的回转中心可以同时设置多个工件零点,既准确方便,又节省辅助加工时间。 相似文献
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Development of a finite element analysis tool for fixture design integrity verification and optimisation 总被引:2,自引:1,他引:2
Nicholas Amaral Joseph J. Rencis Yiming Rong 《The International Journal of Advanced Manufacturing Technology》2005,25(5-6):409-419
Machining fixtures are used to locate and constrain a workpiece during a machining operation. To ensure that the workpiece is manufactured according to specified dimensions and tolerances, it must be appropriately located and clamped. Minimising workpiece and fixture tooling deflections due to clamping and cutting forces in machining is critical to machining accuracy. An ideal fixture design maximises locating accuracy and workpiece stability, while minimising displacements.The purpose of this research is to develop a method for modelling workpiece boundary conditions and applied loads during a machining process, analyse modular fixture tool contact area deformation and optimise support locations, using finite element analysis (FEA). The workpiece boundary conditions are defined by locators and clamps. The locators are placed in a 3-2-1 fixture configuration, constraining all degrees of freedom of the workpiece and are modelled using linear spring-gap elements. The clamps are modelled as point loads. The workpiece is loaded to model cutting forces during drilling and milling machining operations. Fixture design integrity is verified. ANSYS parametric design language code is used to develop an algorithm to automatically optimise fixture support and clamp locations, and clamping forces, to minimise workpiece deformation, subsequently increasing machining accuracy. By implementing FEA in a computer-aided-fixture-design environment, unnecessary and uneconomical “trial and error” experimentation on the shop floor is eliminated. 相似文献
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Evaluating the influence of geometric errors in rotary axes is a common method used by a five-axis machine tool for improving the machining accuracy. In conventional geometric error models, the table coordinate system is considered as the final workpiece coordinate system. In this study, an additional workpiece coordinate transformation was proposed to identify the influence of geometric error. First, a cubic machining test was conducted. Second, the necessity of workpiece coordinate transformation was analyzed, and a method for coordinate transformation was proposed. In addition, both machining simulation and an actual machining experiment of the cubic machining test were conducted to verify the efficiency of the proposed method. The results indicate that the workpiece coordinate transformation is an essential part of the geometric error model for accurately simulating the geometric error influence. The method for identifying the geometric error influence considering the workpiece coordinate transformation is applicable in manufacturing. 相似文献
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Machining fixture layout design using ant colony algorithm based continuous optimization method 总被引:3,自引:2,他引:1
K. P. Padmanaban K. P. Arulshri G. Prabhakaran 《The International Journal of Advanced Manufacturing Technology》2009,45(9-10):922-934
In any machining fixture, the workpiece elastic deformation caused during machining influences the dimensional and form errors of the workpiece. Placing each locator and clamp in an optimal place can minimize the elastic deformation of the workpiece, which in turn minimizes the dimensional and form errors of the workpiece. Design of fixture configuration (layout) is a procedure to establish the workpiece–fixture contact through optimal positioning of clamping and locating elements. In this paper, an ant colony algorithm (ACA) based discrete and continuous optimization methods are applied for optimizing the machining fixture layout so that the workpiece elastic deformation is minimized. The finite element method (FEM) is used for determining the dynamic response of the workpiece caused due to machining and clamping forces. The dynamic response of the workpiece is simulated for all ACA runs. This paper proves that the ACA-based continuous fixture layout optimization method exhibits the better results than that of ACA-based discrete fixture layout optimization method. 相似文献
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X. Cerutti K. Mocellin 《The International Journal of Advanced Manufacturing Technology》2016,82(1-4):489-499
The manufacturing of aluminium alloy structural aerospace parts involves multiple steps, the principal ones being the forming (rolling, forging etc.), the heat treatments and the machining. During this last step, the final geometry of the part is obtained. Before machining, the workpiece has therefore undergone several manufacturing steps resulting in unequal plastic deformation and metallurgical changes which are both sources of residual stresses. On large and complex aluminium alloy aeronautical parts, up to 90 % of the initial workpiece volume can be removed by machining. During machining, the mechanical equilibrium of the part is in constant evolution due to the redistribution of the initial residual stresses.The residual stress redistribution is the main cause of workpiece deflections during machining as well as of post-machining distortion (after unclamping). Both can lead to the non-conformity of the part with the geometrical and dimensional tolerance specifications and therefore to a rejection of the part or to additional conforming steps. In order to improve the machining accuracy and the robustness of the process, the effect of the residual stresses has to be considered for the definition of the machining process plan. In this paper, a specific numerical tool [2] allowing to predict workpiece deflections during machining and post-machining distortion is used to study the influence of the machining sequence on the machining quality in taking into consideration the initial residual stresses. A first machining process plan defined as the reference case is simulated. Simulation results are then compared with experimental ones showing the feasibility to use the developed tool to predict the machining quality depending on the initial residual stresses, the fixture layout and the machining sequence. Using the computational tool, a method to optimise the machining quality depending on the initial workpiece and on the machining sequence is presented. A machining process plan allowing to respect the tolerance specifications is then defined. This demonstrates the feasibility to adapt and to optimise the machining process plan to ensure conformity of the part with the tolerance specifications. 相似文献
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Jin-Ho Lee Sun-Kyu Lee 《The International Journal of Advanced Manufacturing Technology》2004,23(1-2):102-109
This paper describes a system that compensates for machining errors resulting from chucking with separated jaws. In machining a chucked cylindrical workpiece, degradation in machining accuracy, such as out-of-roundness, is inevitable due to variation in the radial compliance of the chuck workpiece system caused by the position of jaws with respect to the direction of the applied force. To compensate for the machining error induced by chucking compliance, the roundness profile of the workpiece due to chucking compliance after machining should be predicted first. Then, using this prediction profile, a compensating tool feed trajectory can be generated. By synchronizing the cutting tool drive system with the rotation of the workpiece, machining errors induced by chucking compliance can be reduced. To satisfy the condition that the cutting tool feed system must provide both high speed and high position accuracy, a brushless linear DC motor is used. In this study, first, the variation in the radial compliance of the chuck workpiece system is obtained through a force-deflection experiment with a workpiece-chucked lathe. Next, using mathematical equations and the results of the cutting experiment, a workpiece profile prediction and its compensating tool trajectory are generated. Then, the configuration of the compensation system based on a linear motor is described, and a proportional integral derivative (PID) controller is designed to improve the system performance. Finally, the tracking performance of the system is confirmed by experiment. A real cutting experiment shows significant improvement in roundness. 相似文献
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INFLUENCE OF WHEEL STRUCTURAL PARAMETERS ON MACHINING ACCURACY OF ULTRA-PRECISION PLANE HONING 总被引:1,自引:0,他引:1
Guo Yinbiao Department of Mechanical Electrical Engineering Xiamen University Xiamen ChinaHu Jianyu Zheng Xiaoguang Katsuo SyojiXiamen University Chongqing University Tohoku University Japan 《机械工程学报(英文版)》2002,15(4):344-347
A new idea for designing wheel patterns is presented so as to solve the problems about machining accuracy ofworkpiece and wear of honing wheel in ultra-precision plane honing. The influence factors on motion principle and pattern structures are analyzed and optimization machining parameters are obtained. By calculating effective cutting lengthon the surface of workpiece cut by wheel's abrasive and the orbit of one point on the surface of workpiece contactingwith wheel, the wear coefficient of different kinds of wheels and accuracy coefficient of workpiece machined by corresponding wheels are obtained. Furthermore, the simulation results show that the optimal pattern structure of wheel turnsout to have lower wheel wear and higher machining accuracy. 相似文献
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电解加工是利用金属在电解液中发生阳极溶解反应而去除工件上多余的材料、将零件加工成形的一种方法。电解加工的加工精度不仅与加工间隙有关,还与机床、工艺装备、工具阴极、工件、工艺参数等诸多因素有关,通常采用混气电解加工、脉冲电解加工、小间隙电解加工和改进电解液等措施提高加工精度。其中混气电解加工是将具有一定压力的气体与电解液按一定比例混合在一起,然后将这种混合物加入到工件的加工间隙中去进行电解加工的一种方法。混气电解加工可以缩小加工间隙,提高电解加工的加工精度和复制精度,但混气电解加工的微观不平度和不直度还不理想。从气液混合比、混气电解加工的特性以及混气电解加工的工艺三个方面对混气电解加工的原理进行一定的探讨,希望摸索一种提高电解加工精度的方法。 相似文献
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Suping Fang Yongsheng Liu Hisashi Otsubo Tsuneto Sumida 《The International Journal of Advanced Manufacturing Technology》2012,61(1-4):303-309
The stage of precision machining center will deform under the weight of large workpiece which is put on it. The deformation will cause the workpiece to incline, and moreover, affect the machining accuracy, which cannot be neglected especially in large-scale combined precision machining centers. To resolve this problem, after simulating the deformation of the stage, this paper introduced an automatic leveling method for the precision stage and gave a method to calculate the regulating variables of each supporting point of the stage. In order to verify these methods, an experiment was done on an experimental stage which was designed and built on the basis of the stage of precision machining center. Experimental results showed that the tilt error of the stage can be reduced with these methods and the machining error of the workpiece declined by 90% after leveling. The experiments also verified the accuracy and feasibility of the automatic leveling method. 相似文献