The Deformation Researches In Mask Projection Stereolithography

Along with development of the modern industrial technology and the computer application level, the progress of the micro-machine has made a great breakthrough. It is an integrated disciplines which assembles the mechanical technology and the computer technology. The micro-machine has a lot of outstanding advantages such as high efficiency, small volume, low energy consumption, higher performance and so on. Therefore, it is widely used in the various industrial fields, and has a broad development prospects. At present, in the scope of the world, the rapid prototyping technology which faces the tiny structure making has become the hot spot of the research and exploitation. Mask projection stereolithography as a kind of the rapid prototyping technology is a new light curing technology, it is the most widely used in present research of the micro-machine.Deformation is an inevitable phenomenon in the rapid prototyping technology, and it is a puzzle should be settled immediately. Deformation restrict the development of photo-curable rapid prototyping technology (SL) seriously. It affects the precision, exterior quality, assembly and practical performance, also its fabrication process is hard to control, so the deformation should be tried to avoid. In order to meet the customers’needs, reduce the deformation and improve production precision of the molding parts, the deformation problem of the mask projection stereolithography is studied systematicly in this paper.Firstly, forming principle of the mask projection stereolithography is described, and the deformation mechanism is expounded theoretically. In addition, the concept of contraction center theory and shrinking stress is analyzed. On the basis of the theoretical analysis of the deformation mechanism, geometry model and mathematical model used for the theoretical analysis are built, so as to a little deflection temperature stress bending differential equation is constructed. And the quantitative relation between the deformation (deflection g) and layer numbers n, temperature difference T and the position dimensions x and y are concluded. In addition MATLAB fitting software is used to fit the mathematical model of the deflection equation g(x,y).Secondly, considering the production condition in the mask projection stereolithography, the method of "life and death unit" in the ANSYS software is used to simulate the contraction deformation. In process of the simulation, a series of simulation datas are obtained through the preliminary treatment(PREP7), solution (Solution) and the post-processing(POST1, POST26). The excel software is used to dispose the simulation datas. The relationship between deformation and the main influence factors were analyzed through the control variable method, which is found that the more layer numbers, the less distortion, and the deformation occurs mainly in the first several layers. In addition, the smaller the temperature difference, the closer the distance from the deformation center, the smaller the deformation.And then, deformation in the mask projection stereolithography is researched with experiments, so the deformation datas in different conditions are got. The relationship between the product’s deformation and the main influence factors are researched, so the correctness of theoretical analysis and software simulation is verified, and the cause of the deformation are expounded in this paper. According to the research conclusion above, a series of measures of decreasing parts deformation are put forward such as setting support, choosing the right process parameters and so on, which can provide the theoretical basis for reducing the deformation of the parts and improving the production precision of parts.Finally, in order to decrease the deformation effectively, two new exposure modes contain regional exposure mode and crisscross exposure mode are studied in this paper. These two kinds of exposure modes mean the same curing layer is divided into multi-area firstly, thus the exposure area is become small, and then these regions are in exposed in different periods of time respectively. So every single curing area can have a free contraction deformation, the internal stress have enough time to release, and finally the whole resin curing layer is formed with smaller deformation. The results of theoretical analysis and experiments show that the two new exposure modes can reduce the deformation of parts effectively.The research has very vital significance for reducing deformation and improving production precision in the mask projection stereolithography.