| Metal Powder Injection Molding (MIM), the combination of traditional powder metallurgy and thermoplastic injection molding, is one of high- tech. As one of the hot researches of current advanced manufacturing technology, it can be used to mass-produce complicated products of fine quality with less cost, which meets the requirements for precise key parts with irregular shape and high performance in many industries such as national defence, communication, machinery, automobile and medical device. Some key issues of flow process in injection molding were studied with theoretic analysis, experimental test and software simulation, which are as follows:In the common assumption research of MIM fluid model, dimensional analysis was firstly adopted in analyzing each item's dimension in momentum equation of feedstock melt in order to study the influence of gravity and inertial force on flow process. The result shows that the dimension of viscosity force is at least 2-3 orders bigger than gravity and inertial force's in flow analysis of MIM while the density of metal powder feedstock is 5-10 times bigger than polymer's. So the viscosity force is a primary control factor. It not only can simplify fluid model with less analytical time and cost, but also makes no need to consider the layout of runners in injection mold design that neglect the influence of gravity and inertial force on flow process of feedstock melt.In the research of rheological equation of MIM feedstock, the flow process of Non-Newtonian fluid was firstly studied by using Cross-WLF Seven-Parameter model. For solution of feedstock viscosity model parameters and shortage of regress function in current molding analysis software, a Quick Self-adaptive Genetic Algorithm was built and the package was developed. Then the algorithm was used to get the seven parameters of viscosity model of W-Ni-Fe heavy alloy and 316L stainless steel feedstock, which provide the necessary material data for quality forecast of mold core part made of stainless steel and heavy alloy tungsten ball, and for optimal design of mold and process parameters, which establishes the foundation of material database of MIM.In the research of visual simulation software development, in order to build the software system model and flow analysis algorithm based on Cross-WLF viscosity model, and realize functions such as pre-processor, solver, parameter regress, data management, graph operations, some advanced software methods as OOSE (Object Oriented Software Engineering) and UML (Unified Modeling Language) were applied to set up user model, static model and dynamic model of MIM simulation software. These models describe system function, event flow, structure and relation of classes, object interaction, structure of database and I/O file format. Finally, simulation software was developed with Visual C++ and Delphi for 2D molding analysis of MIM, which affords facilities for the quality forecast of 2D thin wall parts and optimal design of mold and process parameters.In the research of molding performance of MIM feedstock, for the shortcoming of capillary rheometry, it was propounded that using spiral mold test molding performance of feedstock, and a set of spiral mold was creatively designed with quickly exchange gates and closed mold cavity. With the spiral mold, an orthogonal experiment was made on getting regress equation of flow length Lm of the heavy alloy feedstock. Then the rule of Lm varying with Qm, Pm, and A Tm was discovered. Qm ranks first in the influence on process parameters of molding performance, Pm and A Tm second. Therefore the injection rate Qm should be controlled primarily to improve the flow performance of feedstock.In the application research of MIM simulation software, simulation and injection experiments have been made on the stainless steel mold core and heavy alloy tungsten ball. The former analysis results show that because of "Runway effect" , there is serious disequilibrium flow on two sides in injection molding with single gate, there are four obvious wave crests...
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