Metal Injection Technology, and More

Medical Design Magazine - Apr 1, 2007 12:00 PM, Dan Tasseff Director of Sales FloMet LLC, Deland, Fla. flomet.com

In the late 1970s, a group of engineers in Southern California got the idea to combine powdered metals, sintering technology, and plastic injection molding to produce what most call metal injection molding (MIM). Another firm spent the next ten years refining it into a reliable manufacturing process. Then, in 1991, the firm sold the technology rights to a group that founded FloMet as a standalone manufacturer. Since then, company engineers have focused on formulating feedstocks, mixtures of metal powders and plastic binders. FloMet calls its proprietary version of the process Metal Injection Technology (MIT) to stress it's a special union of material blending (powder metallurgy) with shape forming (plastic injection molding).

MIT works like this: a feedstock goes into an injection-molding machine that melts the binder and pushes the homogeneous material into a mold. Sintering then heats parts close to their melting point under a controlled atmosphere or vacuum until the material's particles bind into a high-density metal or alloy.

MIT differs from traditional MIM in that the older technology uses furnaces that look like long tunnels. Parts are put into containers and pushed or pulled through the furnace. Each end of the furnace is open to the atmosphere, which lets air in, and exposes parts to oxides. These cause finished parts to rust.

In contrast, MIT furnaces built by our company use an outer sleeve (shaped like large soda can) over an inner sleeve, in which molded parts sit. An O-ring seals parts off from the atmosphere. In this way, components being sintered are exposed only to hydrogen and argon, resulting in high density, low-carbon parts. With densities in the 98% range, parts are as durable as wrought iron. Low carbon refers to the carbon content in steel. Stainless steel allows up to 0.4% carbon. MIT parts, on the other hand, contain 0.002% or less carbon, which makes them non-corrosive. In other words, they do not rust.

Another plus for MIT is that it produces complex net-shaped parts in a variety of metals and alloys, and at lower costs than traditional wrought metal and cast parts. Applications range from needles to hearing aids, as well as implantables, and devices for suturing, orthodontic, laparoscopic, and endoscopic procedures. Typical parts weigh from 0.1 to 100 grams and are about 0.030-in. in diameter and 2-in. long. Some parts are even larger.