| Summary: | 碩士 === 國立中央大學 === 機械工程學系 === 106 === Metal Injection Molding (MIM) has taken a place in the production of precision metal parts due to the advantages of high productivity and high complexity. Control of the injection molding stage, the quality, and the feedstock is the important issue. Especially for combination of feedstock which is composed of binder and metal powder also makes the rheology more difficult to know. The situation of powder binder separation often occurs during the filling process. In this study, molding simulation was used to optimize the parameters, and to improve the problem of green parts warpage and powder concentration uniformity for MIM.
The analysis process is separated into two major stages. In the first stage, the initial simulation is performed to verify the short shot of experiments. Furthermore, the working window for injection molding is established. In the second stage, the experimental design of the Taguchi method is adopted to get the optimization for warpage and powder concentration uniformity.
The results of first stage show that the experimental short shot similar to simulated one. In addition, the position of the welding line can also be well predicted. The optimization results of the Moldex3D Design of Expert (DOE) show that the maximum improvement on warpage achieves 11.6%. When these optimized parameters are used in experiments, the maximum improvement on warpage can achieve 57.78%, and the average improvement achieves 20%. Moreover, the optimized parameters can reduce the cycle time of 3s compared with the original design, which brings significant benefits to the dimensional precision and production efficiency.
Before optimization of powder concentration uniformity, the original powder concentration percentage was between 56.8169% and 62.7930% and its average powder concentration was 60.0313%. After optimization, the powder concentration percentage is between 58.6520% and 60.2703% and its average powder concentration is 60.0145%. Therefore, the powder concentration becomes uniform. In other words, this parameter adjustment can reduce the local powder accumulation or the powder binder separation.
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