Using MicroCare Fluids for Dewaxing in Metal Injection Molding (MIM)

Dewaxing Process Enables Major Improvement in Through-put and Safety

A MicroCare client was among the very first companies in the US to deploy Opteon  SF79 fluid. Importantly, this product isn’t used in a traditional degreasing application but in another process. It is used to remove wax from parts made using metal injection molding (MIM). This innovation helps the company reduce operating costs, speed through-put and improve worker safety.

Background:

After years of research, the U.S. Environmental Protection Agency approved the commercialization of a  molecule, called MPHE. MPHE is optimized for critical cleaning. The molecule is marketed as Opteon  SF79 and MicroCare is the authorized source for these fluids in many parts of the world. MicroCare made the first commercial shipments of drums and pails of the new product to customers in the U.S.

With a Kb value of 103, Opteon SF79  fluid is a very powerful degreaser. It can replace aggressive hydrocarbon, chlorinated or brominated solvents including nPB. With an 8-Hour TWA exposure limit of 200 ppm the product generally is safer for people. The cleaner can be used in standard vapor degreasing equipment. These characteristics make Opteon  SF79 an outstanding choice for dewaxing metal parts after injection molding.

The MIM Application:

In previous years, this particular customer produced a large number of precision metal components that required very tight tolerances. Those tolerances were maintained through industry-standard machining processes. But, those processes were expensive, time-consuming and required highly skilled operators.

The client moved to a process of making the same parts and shapes using the MIM process. This process uses a dry powder mixture of different metals. The metal powder is mixed with wax to form a viscous non-Newtonian fluid. The fluid is injected into molds to shape the metal. The semi-finished parts then are sintered at thousands of degrees in a specialized oven where the metal powder melts into a single, unified metal alloy of exactly the right dimensions and strength.

This is very efficient but the wax must be removed prior to follow-on processing.

The Results

After numerous tests, the testers discovered that solvents could penetrate into the porous molded parts, dissolve the wax and remove it from the molded parts. The first attempts used hydrocarbon solvents but these slow drying liquids took days to evaporate out of the molded parts. MicroCare introduced an improved fluid in a vapor degreasing process, using the Bromothane™ precision cleaners which are based on a chemical called nPB. This process worked very well.

However, to enhance worker safety the client wished to migrate to solvents safer than nPB. So MicroCare presented the Opteon  SF79 cleaner. This fluid evaporates quickly, has an excellent toxicity profile, is better for the environment, is affordably priced, and has sufficient cleaning “muscle” to dissolve the wax. This innovation was a win-win for everybody. In terms of cost, it made an enormous difference to the client because almost all of the skilled labor machining costs were replaced. Through-put was improved because instead of taking three days to dewax the process now takes 4-8 hours. Lastly, but most importantly, worker safety is greatly enhanced by the elimination of the nPB-based dewaxing fluid.

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Author: Mike Jones, MicroCare Vice President