&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Historically, the metal injection molding (MIM) is a fairly young injection molding technique which can realize parts with a complex exterior that are otherwise highly difficult to produce, and thus significantly widens the application scope of powder metallurgy. Many hi-tech 3C products and medical appliances require MIM to manufacture metal parts with complex structures and proper strength, currently, and even in the future.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; MIM is a near net-shape manufacturing method combining plastic injection molding process with powder metallurgy process. The MIM process includes several technical steps from the blending of metal powder and plastic binder, mold design, injection molding, and the post-processing of de-binding, sintering and other secondary operation to products. Since MIM involves the widespread process characteristic, product often ends with unstable quality. Especially, the defect of warpage is usually inspected after sintering. However, the quality control of green part is important before the part is sintered. This study aims to improve MIM green part quality in the injection molding step.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; MIM is a special molding technology developed in recent decades, which combines the features of powder metallurgy and conventional injection molding. MIM has taken a place in the production of precision metal parts due to the advantages of high productivity and high complexity. MIM has been developed as a powerful method for manufacturing high value-added metal components. Control of the injection molding process is the important issue. Especially for combination of feedstock which is composed of binder and metal powder also makes the rheological behavior more complicated. Therefore, the situation of powder-binder separation often occurs during the filling stage. The injection molding simulation is an effective tool for predicting the molding process.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; The procedure for analysis is separated into two major steps. In the first step, the flow front simulation is performed to validate the experimental short-shot results. In the second step, the experimental design of the Taguchi method is adopted to get the optimal process parameters for reduction of green parts’ warpage. This approach can avoid the uncertainties relying on operators’ personal experiences.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; The short-shot results demonstrate that the simulated flow front similar to experimental one. In addition, the position of the welding line can also be well predicted. The Taguchi method for minimized warpage show that the improvement on dimensional precision. Moreover, the optimal process parameters can reduce the cycle time of 3 sec compared with the original process parameters, which brings significant benefits to the dimensional precision and production rate.

Optimization of Injection-Molding Parameters for the Warpage of Green Parts of Metal Injection Molding by the Taguchi Method of injection-molding parameters for the warpage of green parts of metal injection molding by the Taguchi method

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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