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Taking Advantage of MIM
For the right applications, the combined process proves advantageous
Design News Staff -- Design News, August 8, 2008
Competing against traditional machining, investment casting, die casting and press and sinter processes, metal-injection molding (MIM) can provide advantages that range from material and weight savings, improved surface finish, greater strength and hardness or elimination of secondary operations, depending on the technology. MIM processing combines the proven technologies of plastic-injection molding and sintered metals. The combination provides the capability to produce complex designs associated with plastic-injection molding with the strength of metal components. Common materials for MIM include alloy and stainless steel, as well as other nonferrous alloys such as titanium. In many instances, MIM provides capabilities for complex molding geometries and co-molding or bonding of dissimilar materials. Depending on the supplier's capabilities, other advantages can be obtained over competing technologies.
SPECIFYING MIM
Advanced Forming Technology views planning as a key element for success with metal-injection molding. Processing steps include compounding fine metal powder with polymer binder, injection molding, debind and sintering. The molded or green part and debound or brown part are the same size but the sintered part can shrink approximately 20 percent. Components designed for MIM processing can take advantage of plastics' capabilities for shape and the properties of the wrought material for strength. Common materials include low-alloy steels, austenitic steels, ferritic stainless steel, iron-cobalt-nickel-based, copper-based and more. With ideal components being those that will weigh from 0.1 to more than 150 gm, high volume provides cost reduction over competing techniques.
AUTOMOTIVE MIM
Well-suited for the high-volume manufacturing of small, complex components, MIM technology is used in high-volume industries including medical device, telecommunications, electronics and automotive parts' manufacturers. In one automotive application, Advanced Forming Technology provides a 316 stainless-steel MIM product that delivers the right physical and chemical properties for a high-pressure hydraulic system connection. Dimensional control was essential for hydraulic lines with the 90-degree insert withstanding burst testing up to 700 bar (10,150 psi). In addition, the combination had to pass pressure tests up to 225 bar (3,260 psi) and thermal cycling from -40 to 100C with pressure spikes during cycling. A MIM process with high statistical control capability provided the answer, including a cost savings.
COMPLEX, YET PRECISE
With the capability to mold metal parts in a variety of materials in sizes ranging from 0.0001 to 0.003 cubic inch while holding tolerances to as little as ±0.0005 inch, Phillips Plastics feels MIM technology can compete with other processing alternatives — especially when two or more components are combined into a single MIM design. Reducing the parts' count and additional assembly that could be required with stamping or conventional powdered metal give the cost advantage to MIM. In addition, MIM has greater design flexibility for molding in complex features such as blind holes, threads and wall thickness changes, instead of requiring additional processing. The more complex parts can also achieve high strength and excellent surface finish.
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