Cost savings from furnaces bale out Mahoney Foundry.

Many aluminum casters build and operate their own gas melting and holding furnaces as a way to limit capital expenditures. However, the higher operating costs and production limitations over time can offset the one time capital savings. That was the experience of Mahoney Foundry, Kendalville, Ind., and the reason that it decided in 1997 to begin a six-year melt system overhaul. It started by replacing its six, site-built, 600-lb. capacity gas fired bowl furnaces with five 1,000-lb. capacity gas fired bale-out crucible furnaces from Morganite Crucible Inc., Wallingford, Corm. Based on the success of those installations, Mahoney replaced its 4,500-lb. commercially built reverberatory furnace with four additional Morganite 1,000-lb. capacity crucible furnaces in 2002.

Mahoney casts aluminum components lot commercial lighting, electrical contacts, electric motors, valving and automotive brakes. For a quarter century, Mahoney had relied on its six site-built furnaces to supply aluminum. The furnaces fed six jolt squeezers, two Rotolift molding machines and one nobake line on a hand fed conveyor.

Because of the limitations of its site built furnaces and the growing demand for its castings, Mahoney decided in 1997 to install Morganite furnaces.

The new furnaces provided the firm with the ability to closely control temperatures and hold metal in the furnaces 24 hrs. a day. The furnaces are filled and held all night with a low flame, and metal temperature is slowly increased through timer controls so pouring temperature can be reached 1 hr. before the morning shift begins. This reduced gas usage by 19% and increased mold production by 23%, representing an annual energy savings of $23,000 at 1997 gas prices.

"A further benefit was longer crucible life," plant manager Steve Mahoney said. "With steady, around-the-clock heat, crucibles no longer suffered thermal shock and typically lasted longer than nine months, compared to 2-3 weeks with the old furnaces. One crucible even lasted a record 15 months."

The ability to closely control metal temperatures also enhanced Mahoney's metal quality. "Our new furnaces cooled to 1,300F (704C) overnight, and the melt had low gas levels when we arrived in the morning. We consistently exceeded our projected internal scrap reductions of 2-3%," Mahoney said.

Mahoney also noted that metal loss dropped by 50% us a result of the better temperature control.

In early 2002, Mahoney installed four gas-fired, 1,000-lb. Morganite crucible furnaces. Mahoney said gas consumption dropped by 39%, and a $42,000/yr. savings in fuel cost was realized. Mahoney also reported that the new furnaces lost only 2% of the metal melted, compared to the 10-12% lost with reverberatory furnace.

Another $3,600/yr. was saved because the Morganite furnaces require just 1 lb. of wall cleaning flux per day while the reverb required 10 lbs. of bath flux and 3-4 lbs. of wall cleaning flux per day. Labor costs dropped as well.

Before the removal of the reverberatory furnace, Mahoney Foundry had one employee tending to the reverberatory furnace and the five Morganite furnaces. With the new furnaces, that same worker tends the furnaces 60-70% of the time, leaving more tune to do other tusks, such as assist the molding line.

Safety, is another area that was improved when the new furnaces were installed. "The large open bath of the reverberatory furnace made molten metal splashes a constant danger, but the Morganite furnaces, with outside shell temperatures of 130F (54C), improved plant salary and working conditions," Mahoney said.

Mahoney also noted that while the firm's actual "molten" capacity had been slightly reduced with the new furnaces, its flexibility and utilization had in creased greatly.

"Today we have nine separate furnaces with individual temperatures, alloys and preparation procedures. We can switch from a 356 alloy to a 319 alloy in just hours or scale up or back the amount of metal we require in a day," he explained. "That gives us better cost control for each casting job. To meet a reduced demand for metal, we just shut one or more furnaces down. And to meet a greater metal demand, we are able to turn our Morganite furnaces three times in an 8-hr. shift. That means 3,000 lbs. of aluminum can be melted and cast per furnace in 8 hrs."

Select No. 002 at www.moderncasting.com/info