Páginas: 7 (1609 palabras) Publicado: 19 de agosto de 2012
In the present work, two analysis methods for analysing fixturing systems in machining processes are presented in order to determine the most suitable clamping regions. The first involves calculating the contact load at the fixture-workpiece interface using a simple and directmathematical tool, which simplifies the deformation minimisation problem. The second method starts from the contact load data obtained and solves several cases in which the clamping position varies. From these data, it is possible to ascertain the interpolating equations, where the load contact is defined as a function of the clamping position. Then, the border curves which limit the valid clampingregions are calculated by imposing two fixturing conditions on the interpolating equations.
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 theworkpiece 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 topredict 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.
Workpiece deformation must be controlled in thenumerical control machining process. Fixture layout and clamping force are two main aspects that influence the degree and distribution of machining deformation. In this paper, a multi-objective model was established to reduce the degree of deformation and to increase the distributing uniformity of deformation. The finite element method was employed to analyze the deformation. A genetic algorithm wasdeveloped to solve the optimization model. Finally, an example illustrated that a satisfactory result was obtained, which is far superior to the experiential one. The multi-objective model can reduce the machining deformation effectively and improve the distribution condition.
In any machining fixture, the workpiece elastic deformationcaused 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 clampingand 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 theworkpiece 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.
In machining fixtures, minimizing workpiece deformation due to clamping and cutting forces is essential to maintain...
Leer documento completo

Regístrate para leer el documento completo.

Estos documentos también te pueden resultar útiles

  • fixture
  • Fixture
  • Fixtures
  • fixture
  • Fixture
  • Fixture
  • Fixture
  • Fixture 2012

Conviértase en miembro formal de Buenas Tareas