Money no longer has to go up in smoke inside the ovens at Harris Metals thanks to the research of Mechanical Engineering Associate Professor Glenn Cunningham and Manufacturing and Industrial Technology Associate Professor Fred Vondra.

Through a Department of Energy Industries of the Future Aluminum grant, Cunningham and Vondra recruited Harris Metals, along with four other small- to medium-sized companies, for a program offering energy assessments and money-saving ideas unique to the industry. At Harris Metals, the focus quickly turned to the furnace and bake-out ovens that consumed a lot of energy and maintenance hours.

“It was costing around $30,000 a year in natural gas to run four large ovens used to break down the sand molds,” says Cunningham. “Although we analyzed the furnace’s efficiency with an infrared camera to reduce costs, it became apparent that we might eliminate the need altogether for the ovens if we could find a different way to break the sand molds away from the metal castings.”

In the industry, molten aluminum or iron is poured into almost rock-hard sand molds to create a casting. Sand molds are formed from “green sand,” which is mixed with a binder to make it sticky and hold its shape. When the sand/binder mixture sets up and hardens, the hot liquid metal is poured into the mold.

After the metal cools, sand molds mixed with a traditional binder break away only after being baked at 600-700 degrees for five to six hours inside the bake-out ovens. The finished products are then placed on shake-out tables were the sand is removed from inside and out by shaking.

“With this process, there’s often a queue of castings waiting to be processed,” says Harris Metals President Dale Kondas. “Often there would be a week or more wait that affected our inventory and how quickly we could respond to orders.”

Vondra noticed the sand within many castings was too hard to shake out without extensive baking. Making the sand/binder mixture softer and easier to remove also presented challenges.

“The goal is to keep a handle on the different variables that change each time you change the composition of the sand,” says Vondra. “You have to be careful not to weaken the mixture because it must withstand the process and handling, but fall apart at just the right moment.”

Vondra saw the process could be improved by using a binder that would break down gradually from the heat of the aluminum poured inside, completely eliminating the time and money spent baking each mold. He worked with Fairmount Minerals in Illinois, where a former student of his worked, to choose the appropriate binder for Harris Metals’ needs, and gradually the new sand/binder molds were worked into production. The results were astounding.

“Because we no longer need natural gas to fire the ovens, our expenses dropped almost $30,000 a year,” says Kondas. “Plus, we’ve reduced our lead time by a week and a half by eliminating the baking step, and we detect problems and make corrections faster.”

In addition to the savings and efficiency created by using the new binder, Cunningham and Vondra detected loss of heat and energy at other sources with the infrared camera. Kondas says they solved a recurring problem with a 600 amp fuse that kept blowing by using the device.

“The cooperation I receive from Tennessee Tech has created a terrific relationship that is responsive to industry needs,” says Kondas.