Research On The Flexible Fixture Technology Based On Phase Change Materials

Flexible fixture is a vital part in modern manufacturing, it directly affects development cycle, process efficiency, quality and cost of the new production. Existing flexible fixture is mainly modular fixture. It is difficult to achieve high-precision, adjustment and optimization of clamping arrangement due to the drawbacks of poor rigidity and the limits of holes and sinks. Further research of several main phase fixture was needed because of the poor rigidity of clamping, a large waste of materials during processing and useless cutting. Both authentic phase-change clamp and pseudo phase-change clamp are used for fixing the work-piece directly. There have been no studies on indirect clamping by fixing fixture components.So an idea of new type of flexible fixture is proposed in this paper. Adding low-melting point alloy as phase change materials after prior clamping. Connection is achieved when materials are cooled between fixture components, clamping body and work-piece. The idea will truly reflect the flexibility of the work-piece clamping. That is, a set of fixture can clamp arbitrarily shaped work-piece in certain size range. Based on the above idea, the main contents of the paper are as follows:1. Studying the quick cooling methods of phase change materials and selecting the relative optimal cooling method that is shower cooling at zero degrees centigrade.2. Optimizing the critical components of flexible fixture which is locators, clamps and clamping body. And designing the floor of clamping body and four kinds of framework structures. And also designing a series of locators and clamps as characteristics of phase change materials fixture.3. Illustrating the positioning strategy in several ways of the choice of locating datum,the arrangement of locators, the judgment criterion of deterministic location and the evaluation of fixture locating stability. Describing the selection principles and methods of locating datum and the arrangement of locators. The methods of the judgment criterion of deterministic location and the evaluation of fixture locating stability are given.4. Presenting the clamping strategies aimed at the characteristics of phase-change material fixture which can be arranged freely. Then analyzing the contact spinor and constraints in the process of the clamping. The clamping stability model is established with friction-less and friction. Determining whether the clamping sequence is reasonable by using the theory of linear programming to solve the model. Calculating every clamping force by using the clamping stability model under cutting forces. Finally, illustrating the stability in the clamping process and machining process by using example.