Using a range of low alloy steels, stainless steels, tool steels, magnetic alloys and tungsten alloys, the Metal Injection Molding (MIM) process produces complex three dimensional shapes. Like plastic injection molding and high-pressure die casting, MIM processing can produce similar shapes and configuration features, according to the Metal Powder Industries Federation (MPIF).
For the right type of products, the MIM process simplifies the manufacturing process and reduces or completely eliminates machining operation(s), providing a significant cost reduction. Some of the newest aspects include the latest materials that are being used, especially for higher-end applications such as super alloys and aerospace materials. A superalloy, or high-performance alloy, can withstand extreme temperatures. However, consumer and medical applications continue to drive the technology, as well.
MIM Migration
With the addition of a new debind sintering furnace early next year, Phillips Plastics Corp. will basically double their capacity, says Tony Pelke, engineering manager, MIM area of Phillips Plastics. “We are seeing a lot of opportunities for quotes and it seems like people are certainly designing more for the process than what they were several years ago,” he says. Parts that approach 250 gm are not common, because the raw material cost is expensive and it becomes more economical to use investment casting or other metal-forming technology, says Pelke. Also, it is difficult to maintain dimensional control on extremely large parts that encounter internal micoporosity and voids. “The best fits for the MIM’s process is relatively small, less than 30 gm, intricate, complex, very detailed geometry,” says Pelke. This is the focus area for Phillips Plastics. Its MIM Design Guide provides insight to potential and existing MIM users.
Single-Piece Unit
Indo-US MIM Tec reduced a dot matrix printer part that originally consisted of two sheet metal parts and nine pins riveted from the back side to a single-piece assembly using MIM technology. Machining of the initial assembly for critical dimensions had an overall process yield of less than 60 percent. With post sintering, the MIM part is finish machined to eliminate gate remnants on the back side improving the overall yield to more than 90 percent. As a result, the production cost was reduced more than 50 percent. With mold design principles similar to plastic injection molding, typical wall thickness for the company’s MIM process ranges from 0.5 to 8.0 mm. Tolerances within ±0.3 percent of the base dimension can be achieved in the “as sintered” condition.
Medical MIM
Alberox Products div. of Morgan Advanced Ceramics uses metal injection-molded technology to manufacture laproscopic instruments for medical applications. Constructed from a variety of metals including 17-4PH, 304L and 316L stainless steels, these instruments meet the specific needs of the medical market. The MIM process components require virtually no additional machining and several components can be molded together as one unit. Molds with multiple cavities can reduce tooling costs while meeting medical customer’s specifications. A MIM design guide informs engineers of the capabilities of Metal Injection Molding and explains the criteria useful in designing a part in order to optimize the MIM process and achieve a cost-effective product.
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