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In special applications where 100 percent density is required, a hot isostatic pressing (HIP) process is used.Įconomical for small, complex parts in high volumesĭebinding furnace. Parts that distort during sintering can be coined or otherwise straightened afterward. MIM parts are often used as-sintered, but machining, heat treating, plating and other processes can be applied to the sintered part. They have a smooth surface finish, typically around 32 RMS (root mean square roughness).
#METAL INJECTION FULL#
After sintering, most MIM parts end up at 95 to 98 percent of full density they contain 2 to 5 percent of equally dispersed voids (pores). In the sintering furnace, the temperature rises until the remaining binder is gone and the metal particles approach 90 percent of their melting temperature, at which point they join together. For example, metals that form oxide on the surface of the particles might be sintered in a hydrogen atmosphere to remove the oxide layer. Sintering may be done in a vacuum or in a hydrogen or other gaseous atmosphere, depending on the requirements of the metals. The part is now a “brown” part and is about 40 percent porous.įinally, the parts are set on ceramic trays, supported by fixtures if necessary, and placed in a furnace to remove the last of the binder and sinter the parts. Debinding can be done with heat (thermally) or by a chemical process, either with solvents or with chemicals that react with the binder.Īfter first stage debinding, a small amount of binder remains to help the part hold its shape. This removes most, but not all, of the binder from the part. The next step is called first stage debinding. At this stage they are called “green” parts. The newly molded parts are the shape of the final part, but larger. The feedstock is heated and forced into the mold cavities.
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The binder is a mixture of materials such as plastic and wax materials that melt and hold the metal particles in suspension while the stock flows into the mold cavities A typical feedstock might be 60 percent metal powder and 40 percent binder by volume. The MIM process starts with mixing the feedstock, a combination of metal powder and binder. These very fine powders are made by a number of processes, including atomizing molten metal with a high-velocity stream of gas. “It feels like talcum powder,” said David Smith, senior sales manager at PCC Advanced Forming Technology (AFT), Longmont, Colo. MIM metal powder is very fine, with particles 20 microns (about 0.0008″) in size or smaller. MIM can also make it possible to replace an assembly of two or more parts with a single MIM part, eliminating the cost of assembling those parts. Since MIM can be used to fabricate complex parts economically in structural metals, it can provide significant cost savings to the savvy manufacturer. This does not include parts companies manufacture for their own in-house use. The worldwide market for custom MIM parts is more than $500 million, according to James Dale, vice president of member and industry relations, Metal Powder Industries Federation (MPIF), Princeton, N.J. MIM uses much finer powder than PM, and a completely different manufacturing process. There are several related processes that also use metal particles. PM parts are formed of metal powder compressed in a die and then sintered. You may be familiar with powdered metal, or PM, parts, especially as bearings, bushings and small gears. Industries that now use MIM parts include aerospace, medical, electronics, firearms and consumer products. MIM has been around for decades, but only in the last twenty years has found widespread commercial application. The process is called metal injection molding (MIM), or sometimes powder injection molding (PIM), and it can produce intricate parts in a wide range of metals, including steel, stainless steel, and even high-temperature alloys. Injection molding by mixing metal powder with plastic, molding it and then removing the plastic and sintering the part. To make a complex part in metal, you can cast it, or machine it - or injection mold it. Blade clamp for a power tool: Replacing a multiple-component assembly with a metal injection molded part.