Master Caster

Intermet Corp.'s headquarters in a heavily wooded office park in Troy, MI, is nearly impossible to see from the road.

The building's setting is analogous to Intermet's product offerings. The supplier makes components that are largely invisible to consumers, such as brake parts, camshafts, differential cases, knuckles, transmission components and structural frames.

It's also not well known throughout the industry that Intermet, historically recognized for decades as a supplier of iron components, also casts aluminum, magnesium and zinc parts.

Intermet refers to its position as “master caster,” says Gary Ruff, the company's president and chief operating officer.

It's an interesting slot for Intermet to fill considering many auto makers have narrowed their casting expertise, leaving a gap Tier 1s have been reluctant to fill. In some cases, Intermet is in the ironic position of taking away business from itself by replacing cast-iron applications with aluminum or magnesium parts.

Ductile iron still dominates Intermet's sales. In 2001 it accounted for 59% vs. 34% for aluminum and magnesium combined. But Intermet forecasts iron will account for 50% of its sales in 2003, eventually dropping as low as 40%.

Leading Intermet's shift away from iron is a new process the company developed for aluminum structural components called Pressure Counter Pressure Casting (PCPC). It controls how molten aluminum fills a casting to ensure uniform metal flow, and it prevents the entrance of gases. The result, Intermet claims, is outstanding strength and ductility for components, such as steering knuckles, and a roughly 40% weight savings.

“Even if you think you're filling uniformly, you're really not because there's always changes in section sizes,” explains Ruff, who spearheaded the PCPC effort along with Thomas E. Purcha, director-Process Research, and Donald L. Roberts, director-Manufacturing Development.

Ruff uses a garden hose as an analogy. When there is no nozzle on the end, the water flows out uniformly. If the end of the hose is manipulated by a nozzle or a person's thumb, the water flows out faster, farther and unevenly. When a metal enters a cast, it may appear to flow uniformly. But as the metal fills the cast and moves through interior channels or curves that are narrow or sharp, pressure increases and the metal rushes through the passage and into the next chamber of the cast at an irregular rate.

Traditional light-metal casting and molding processes, such as hot- and cold-chamber die casting and low-pressure, vacuum and squeeze casting, have turbulent and non-uniform metal flows.

PCPC uses a similar mold positioning and sealed furnace, like low-pressure and vacuum low-pressure processes. With PCPC, the casting cavity is placed entirely inside a pressure chamber.

Upon closure of the casting cavity, the casting chamber and furnace chamber are pressurized with equal force. The pressure in the casting chamber is slowly exhausted while the pressure in the casting furnace is increased. This allows metal to rise in the filling tubes and into the casting cavity at a controlled rate. Multiple cavities and multiple fill tubes can be used.

Intermet didn't supply any aluminum knuckles in 2000. With PCPC, its goal is to supply 5 million by 2005. Current annual volume is about 1.8 million for steering knuckles on many GM midsize cars and minivans. Intermet will add steering knuckles for another GM vehicle as well as Chrysler Group's Dodge Durango within 12 months.

It also plans to expand use of PCPC for chassis and suspension components.