Porcelain Enameling
Continuous Advantages

by Jill Russell, Assistant Editor

Radically redesigning its powder porcelain system, Maytag Corporation has significantly improved its production time and product quality at its Cleveland, TN, U.S. plant.

Producing freestanding gas and electric ranges, Maytag, with the help of supplier KMI Systems, Inc. (Crystal Lake, IL, U.S.), has eliminated the traditional problems associated with transfer coating systems such as knocking off loose powder, marring the coating, and excessive amounts of scrap material.

“ The whole thought process was, ‘what can we do to either minimize the problems we’re having with this or eliminate the process altogether,’” says Jeff Sellins, manager, Finishing Engineering Cleveland Cooking Products for Maytag.

Initially discussing the idea of a continuous powder porcelain system 5 years ago, the finishing system was installed in July 2000, with another system following shortly after in July 2002. “The no-transfer system at Maytag provides a high-quality porcelain enamel finish for the consumer that is very cost competitive with conventional powder paint,” explains Mike Horton, manager of Inorganic Systems, KMI Systems, Inc.

“ The no-transfer systems offer a porcelain enamel finish at a lower cost with higher gloss and quality over powder or wet, high-temperature paint finishes,” he continues. “A future porcelain enamel installation could be installed with less manufacturing area by using the no-transfer process.”

During the 2 years it took from system concept to installation, several obstacles had to be overcome in regard to the system hangers and the furnace and cleaning processes.

Since the system is continuous and parts are no longer moved from one type of hanger to another, the hangers had to be redesigned in order to withstand the furnace heat, which reaches temperatures exceeding 1,500°F to 1,550°F. “Normally, [in a transfer system] you use cold-rolled steel tools for the application process and cast-alloy tools for the furnace, which will withstand the heat,” explains Mr. Sellins.

Naturally, Maytag decided to simply install alloy hangers in the new system, as the metal would be durable enough to withstand the heat. However, this brought on another challenge. As the part is sprayed with the powder porcelain, the hanger and tools are coated as well. Therefore, Maytag and KMI needed to devise a way in which the tools could be cleaned, preserving them for future use.

“ Alloy tools are not expendable because they are very, very expensive,” says Mr. Sellins. “Once you fabricate the tooling, you probably have five to seven times the cost in an alloy hanger versus a regular, cold-rolled hanger. Also, you don’t want to have to take the hanger on and off the line to clean it, so you have to consider a continuous process, uninterrupted with as little labor input as possible,” he tells APPLIANCE.

As a solution, Maytag decided to use a steel-shot process to clean the porcelain off the hangers. “We had a good idea of what we wanted and what material we wanted to use. It was strictly trial and error as far as minimizing the wear and tear on the hangers [from the cleaning],” Mr. Sellins explains.

Once the challenges were overcome and preliminary testing was completed, the continuous system was installed and used as the primary means to keep production up. “In order to make the system work and to prove the design, we made tooling adjustments and tested them over several months. Once the existing conveyor system was demolished, Maytag depended on the success of the no-transfer system to keep the range plant running. This was a major risk with a big payback,” Mr. Horton tells APPLIANCE.

In fact, Maytag quickly started plans to install a second continuous system by the following year. “The first system was a major learning curve. The second system went in very, very easily,” says Mr. Sellins. “There were hardly any start-up problems.”

According to the appliance maker, the only other consideration with a continuous system is performing maintenance issues. With a traditional system, if a problem occurs, the line is shut down. On the contrary, with a continuous system, shutting one part of the line affects every part of the process. “The bottom line,” says Mr. Sellins, “is you don’t shut it down. You figure out a way to do maintenance on that line without stopping it. And the only reason the line stops is if you have a hang up and can’t run.”

As a result of using the new powder porcelain system, Maytag reported an increase in production and a decrease in both downtime and scrap. “We saw a yield improvement right away,” confirms Mr. Sellins. “Our yields on our back guards went from 80 to 85 percent to 95 to 97 percent because they were the main parts we damaged when we transferred because there were so many of them on our hanger,” he says.

The company also reduced scrap considerably. Overall, scrap was reduced 40 percent more than originally anticipated and downtime was reduced by 20 percent. “That was a major benefit in terms of our operating efficiency and our capacity improvement,” says Mr. Sellins.

In response to the overall effectiveness of the system, Mr. Sellins believes Maytag’s new continuous line is the most advanced in the industry. “I believe we’re the only company utilizing it,” he says. “I’m amazed that more people aren’t at least looking into it. But that’s okay, that gives Maytag an advantage.”