共查询到20条相似文献,搜索用时 15 毫秒
1.
N. Kaya F. Öztürk 《The International Journal of Advanced Manufacturing Technology》2003,21(6):411-419
In this paper, a workpiece–fixture layout verification approach with the application of frictional contact and chip removal
effects using a finite-element technique, is presented. The objective of the proposed system is to overcome the deficiencies
of existing fixture design approaches. Workpiece–fixture layout verification analysis is carried out for time varying machining
forces to ensure that the workpiece will be held against the cutting and clamping forces. The chip removal effect and frictional
contact between the workpiece and the fixture elements are taken into account using a material removal approach based on element
death technique and nonlinear finite-element analysis. A case study illustrates the application of the proposed approach.
ID="A1"Correspondance and offprint requests to: Professor F. ?ztürk, Department of Mechanical Engineering, Mühendislik-Mimarlik Fakültesi, G?r¨kle Kampusu, Bursa 16059,
Turkey. E-mail: ferruh@uladag.edu.tr 相似文献
2.
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
3.
B. Li S. N. Melkote S. Y. Liang 《The International Journal of Advanced Manufacturing Technology》2000,16(2):79-84
This paper presents a model for analysing the reaction forces and moments for machining fixtures with large contact areas,
e.g. a mechanical vice. Such fixtures transmit torsional loads in addition to normal and tangential loads and thus differ
from fixtures using point or line contacts. The model is developed using a contact mechanics approach where the workpiece
is assumed to be elastic in the contact region and the fixture element is treated as rigid. Closed-form contact compliance
solutions for normal, tangential, and torsional loads are used to derive the elastic deformation model for each contact. A
minimum energy principle is used to solve the multiple contact problem yielding unique predictions of the fixture–workpiece
contact forces and moments due to clamping and machining forces. This model is then used to determine the minimum clamping
force necessary to keep the workpiece in static equilibrium during machining. An example is given to demonstrate its effectiveness
in analysing the clamping performance of a mechanical vice during machining. 相似文献
4.
Shaopeng Tian Zhengdong Huang Liping Chen Qifu Wang 《The International Journal of Advanced Manufacturing Technology》2006,30(1-2):76-86
In this paper, we present an approach for optimally selecting the locating positions of workpieces and identifying feasible clamping regions that meet the requirements of the form-closure principle for fixture layout. This approach firstly finds an optimal configuration of locating points on a set of faces of the workpiece which minimizes the error transfer from locating points to machining features. In the formulation of the optimization, the error transfer is modeled using an error transfer matrix. The eigenvalues of the matrix are used as objective functions of the optimization. Secondly, this approach computes the clamping wrench cone and its member wrench can form a form-closure fixture layout, together with the formerly selected locating points. Finally, it generates the feasible clamping regions by projecting the clamping wrench cone onto faces of the clamping feature faces. An example is included to illustrate the effectiveness of the proposed approach. Compared with traditional methods in which only error transfer from the locating points to the workpiece’s mass-center is considered, the error transfer control in this approach is more effective and of greater efficiency. In addition, the clamping wrench cone projection method for the generation of feasible clamping regions is more suitable for handling cases with concave clamping faces than traditional convex-combination-based methods. 相似文献
5.
Y.G. Liao S.J. Hu 《The International Journal of Advanced Manufacturing Technology》2001,17(11):810-818
Surface quality is a major factor affecting the performance of a component. The machined surface quality is strongly influenced
by the external loads during the fixturing and machining processes. In machining process development, it is highly desirable
to predict the quality of a machined surface. For this purpose, an integrated finite element analysis (FEA) model of the entire
fixture–workpiece system is developed to investigate the influence of clamping preload and machining force on the surface
quality of the machined workpiece. The effects of fixture and machine table compliance (from experimental data), and the workpiece
and its locators/clamps contact interaction, and forced vibration, on the machined surface quality are taken into account.
This simulation model provides a better understanding of the causes of surface error and a more realistic prediction of the
machined surface quality. The deck face of a V-type engine block subjected to fixture clamping and a face milling operation
is given as an example. A comparison between the simulation result and experimental data shows a reasonable agreement. 相似文献
6.
阐述在轮毂的数控车削加工过程中,由于受到夹具的夹紧力和切削力的作用,致使工件在加工时产生变形,尺寸精度大大超差,严重时甚至工件会脱落于夹具,导致工件报废。经过本人认真研究,通过改进夹爪、调整工件夹紧位置,适当改变夹头夹紧力及优化加工工艺等,从而大大提高了加工精度和生产效率,降低了劳动强度,节约生产成本。希望以上的方法能对从事相关工作的人员有一定的借鉴作用。 相似文献
7.
S. Selvakumar K. P. Arulshri K. P. Padmanaban K. S. K. Sasikumar 《The International Journal of Advanced Manufacturing Technology》2013,65(9-12):1573-1586
In machining fixtures, minimizing workpiece deformation due to clamping and cutting forces is essential to maintain the machining accuracy. This can be achieved by selecting the optimal location of fixturing elements such as locators and clamps. Many researches in the past decades described more efficient algorithms for fixture layout optimization. In this paper, artificial neural networks (ANN)-based algorithm with design of experiments (DOE) is proposed to design an optimum fixture layout in order to reduce the maximum elastic deformation of the workpiece caused by the clamping and machining forces acting on the workpiece while machining. Finite element method (FEM) is used to find out the maximum deformation of the workpiece for various fixture layouts. ANN is used as an optimization tool to find the optimal location of the locators and clamps. To train the ANN, sufficient sets of input and output are fed to the ANN system. The input includes the position of the locators and clamps. The output includes the maximum deformation of the workpiece for the corresponding fixture layout under the machining condition. In the testing phase, the ANN results are compared with the FEM results. After the testing process, the trained ANN is used to predict the maximum deformation for the possible fixture layouts. DOE is introduced as another optimization tool to find the solution region for all design variables to minimum deformation of the work piece. The maximum deformations of all possible fixture layouts within the solution region are predicted by ANN. Finally, the layout which shows the minimum deformation is selected as optimal fixture layout. 相似文献
8.
James N. Asante 《The International Journal of Advanced Manufacturing Technology》2008,39(5-6):578-588
Contact forces between workpiece and fixture define fixture stability during clamping and influence workpiece accuracy during machining. In particular, forces acting in the contact region are important for understanding deformation of the workpiece at the contact region. This paper presents a model that combines contact elasticity with finite element methods to predict the contact load and pressure distribution at the contact region in a workpiece-fixture system. The objective is to determine how much clamp forces can be applied to generate adequate contact forces to keep the workpiece in position during machining. The model is able to predict the normal and tangential contact forces as well as the pressure distribution at each workpiece-fixture contact in the fixturing system. Model prediction is shown to be in good agreement with known industry practice on clamp force determination. The presented method has no limits on the types of materials that can be analyzed. 相似文献
9.
B. Li S.N. Melkote 《The International Journal of Advanced Manufacturing Technology》2001,17(2):104-113
Workpiece motion arising from localised elastic deformation at fixture-workpiece contacts owing to clamping and machining
forces is known to affect significantly the workpiece location accuracy and, hence, the final part quality. This effect can
be minimised through fixture design optimisation. The clamping force is a critical design variable that can be optimised to
reduce the workpiece motion. This paper presents a new method for determining the optimun clamping forces for a multiple clamp
fixture subjected to quasu-static machining forces. The method uses elastic contact mechanics models to represent the fixture-workpiece
contact and involves the formulation and solution of a multi-objective constrained oprimisation model. The impact of clamping
force optimisation on workpiece location accuracy is analysed through examples involving a 3-2-1 type milling fixture. 相似文献
10.
夹具布局和夹紧力大小影响切削变形的大小和分布.基于遗传算法和有限元方法,提出一种夹具布局和夹紧力优化设计方法.该方法将同步优化夹具布局和夹紧力大小以及施加变夹紧力相结合,首先以加工变形最小化和变形分布最均匀为目标同步优化夹具布局和夹紧力大小,然后在优化后的夹具布局的基础上求解使得加工变形最小的变夹紧力大小.使用该方法进行底座薄壁零件的夹具优化设计,结果表明优化得到的设计优于经验设计和多目标优化方法,该方法有效地降低了加工过程中工件的变形,提高变形均匀度. 相似文献
11.
针对主减速器壳体在立式多刀半自动车床上加工时,采用标准液压三爪卡盘无法有效定位夹紧工件的问题,依据工件的结构特点,设计制造一种能在一次装夹下完成粗精两序加工的专用车削工装夹具,彻底解决了由于多刀同时粗加工、车削抗力大,工件夹持不可靠的安全问题。通过夹紧力的高低压转换,有效防止工件夹紧变形。生产实践证明,该夹具简单可靠,便于操作,提高了生产效率,保证了加工精度。 相似文献
12.
A Clamping Design Approach for Automated Fixture Design 总被引:2,自引:1,他引:1
J. Cecil 《The International Journal of Advanced Manufacturing Technology》2001,18(11):784-789
In this paper, an innovative clamping design approach is described in the context of computer-aided fixture design activities.
The clamping design approach involves identification of clamping surfaces and clamp points on a given workpiece. This approach
can be applied in conjunction with a locator design approach to hold and support the workpiece during machining and to position
the workpiece correctly with respect to the cutting tool. Detailed steps are given for automated clamp design. Geometric reasoning
techniques are used to determine feasible clamp faces and positions. The required inputs include CAD model specifications,
features identified onthe finished workpiece, locator points and elements. 相似文献
13.
基于遗传算法的夹具布局和夹紧力同步优化 总被引:7,自引:0,他引:7
夹具设计是机械加工中一个重要步骤。夹具优化旨在得到最合理的夹具布局和夹紧力。为了弥补分步优化夹具布局和夹紧力以及应用传统优化算法而存在的不足,本文提出了应用遗传算法同步优化夹具布局和夹紧力的方法。使用该方法进行夹具优化的算例结果表明优化得到的设计优于经验设计,该方法是一种有效的夹具优化方法。 相似文献
14.
15.
J.J.-X. Liu D.R. Strong 《The International Journal of Advanced Manufacturing Technology》2003,21(6):426-437
This paper presents a fixture configuration verification methodology for nonlinear fixture systems, which is developed on
the basis of optimal clamping forces and total restraint. This method can be applied for validating the feasibility of a fixture
with point, line and area contacts in two stages: fixturing and machining. The "∞-∞-∞" principle for nonlinear fixture location
is proposed. The automatic fixture verification system is modelled as a nonlinear optimisation problem with respect to minimum
clamping forces. The method provides a simple and effective means for: (a) verifying whether a particular fixturing configuration
is valid with respect to locating stability, deterministic workpiece location, clamping stability and total restraint and
(b) determining minimum variable clamping forces over the entire machining time. Two case studies are presented to demonstrate
the effectiveness and the capabilities of the methodology.
ID="A1"Correspondance and offprint requests to: Prof. D. R. Strong, Department of Mechanical and Industrial Engineering, The University of Manitoba, Winnipeg, Manitoba,
Canada R3T 5V6. E-mail: strong@ms.umanitoba.ca 相似文献
16.
Y. Kang Y. Rong J. C. Yang 《The International Journal of Advanced Manufacturing Technology》2003,21(10-11):842-849
In fixture design, a workpiece is required to remain stable throughout the fixturing and machining processes in order to achieve safety and machining accuracy. This requirement is verified by a function of the computer-aided fixture design verification (CAFDV) system. This paper presents the methodologies of fixturing stability analysis in CAFDV. A kinetic fixture model is created to formulate the stability problem, and a fixture stiffness matrix (FSM) is derived to solve the problem. This approach not only verifies fixturing stability, but also finds the minimum clamping forces, fixture deformation, and fixture reaction forces. The clamping sequence can also be verified with this approach. 相似文献
17.
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
18.
Zhihui Liu Michael Yu Wang Kedian Wang Xuesong Mei 《The International Journal of Advanced Manufacturing Technology》2013,67(5-8):1267-1279
The fixture determines the workpiece position in a machining process; therefore, an increasing amount of attention has been given to fixture layout design. While machining, the workpiece position is affected by two major sources: (a) the locator displacement and (b) the force–deformation of the workpiece–fixture system. In the beginning of this paper, a geometric model considering the shape of a locator is developed to analyze the location performance, followed by the presentation of a simplified solving method and a location layout performance index. Second, to complete the force–deformation analysis, a finite element method-based force–deformation model is built and accelerated by a new method with a lower computer memory cost. Based on these two models, multiple objects of fixture layout optimization problems are proposed, and a multi-objective genetic algorithm-based optimization method is constructed. Finally, testing examples are approved to examine the validity of the method represented in this paper. These methods can provide a more accurate prediction of the locating performance in more widely used cases, and they have faster calculating speeds with lower computer memory costs. 相似文献
19.
Low weight and good toughness thin plate parts are widely used in modern industry, but its flexibility seriously impacts the machinability. Plenty of studies focus on the influence of machine tool and cutting tool on the machining errors. However, few researches focus on compensating machining errors through the fixture. In order to improve the machining accuracy of thin plate-shape part in face milling, this paper presents a novel method for compensating the surface errors by prebending the workpiece during the milling process. First, a machining error prediction model using finite element method is formulated, which simplifies the contacts between the workpiece and fixture with spring constraints. Milling forces calculated by the micro-unit cutting force model are loaded on the error prediction model to predict the machining error. The error prediction results are substituted into the given formulas to obtain the prebending clamping forces and clamping positions. Consequently, the workpiece is prebent in terms of the calculated clamping forces and positions during the face milling operation to reduce the machining error. Finally, simulation and experimental tests are carried out to validate the correctness and efficiency of the proposed error compensation method. The experimental measured flatness results show that the flatness improves by approximately 30 percent through this error compensation method. The proposed method not only predicts the machining errors in face milling thin plate-shape parts but also reduces the machining errors by taking full advantage of the workpiece prebending caused by fixture, meanwhile, it provides a novel idea and theoretical basis for reducing milling errors and improving the milling accuracy. 相似文献