Molding, the fourth part of our blog series on MIM, is focused on the pellets of the compounding being loaded into a MIM machine and producing a “green part”. This part is about 20% larger than the final part, but has the same geometry as the final. The percentage is based on the type of metal that is used, and each metal’s percentage will be known before the mold is completed. This allows for the tool to be created correctly, so that the final part meets the exact specifications of the customers needs.
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When the pelletized feedstock is fed into either our standard or multi-slide MIM machines, it is heated and then injected into a mold cavity. This injection happens at a high pressure, which is when the part is referred to as “green”. The part is then allowed to cool, which happens very quickly. After it has cooled it is ejected from the mold. Only the binders melt in the molding phase, and the tooling can have multiple cavities, which means higher production rates. As a general note, 70% of MIM defects are a result of tooling and another 15% is a result of molding. These two pieces are extremely important to ensuring that the final part is correct and free of defects. Now, let’s learn more about the MIM machines we offer at OptiMIM.
OptiMIM utilizes conventional MIM machines that have a typical cycle time of about two shots per minute. It is ideal for larger parts and for parts that have multi-cavities and are also high-volume production. Conventional MIM machines require complex tooling, long runner systems, and long material residence time in the machine and mold. Some of the tools for conventional MIM machines could have shorter lives depending on the complexity of the part.
In part five of this series, you’ll learn how the part goes from “green” to “brown”. The next blog will focus on the debinding portion of the MIM process. What else would you like to know about molding? Are there additional pieces you would like to get more details on? If so, please let me know. I’m here to answer all of your MIM questions.
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