"Thicker in the Press," Feature Article, October 2003

thicker in the press

A sheet extrusion process can add strength where it's needed.

by John DeGaspari,
Associate Editor

It's not uncommon for a press to combine stamping, deep drawing, and cold forming to produce complex parts. But sheet metal extrusion processes are normally expected to thin out a sheet as it runs through the press.

According to Textron Fastening Systems in Troy, Mich., the company is bringing to the United States a system that can thicken parts in areas where more strength is needed. Textron, which has been operating the system in Germany, is installing a 1,000-ton press at its Jackson, Mich., stamping facility and plans to offer the process by May of next year, in time for automakers' 2005 models.

The process was developed by Sükosim, a German company acquired by Textron about five years ago. Textron has five presses for the system, ranging from 500 to 1,000 tons, at a site in Dürbheim, Germany. The company is installing a sixth press, of 3,000 tons, there later this year. Müller Weingarten, which built the presses in Germany, has a U.S. unit in Madison Heights, Mich., that is building the press in Jackson.

In Germany, the Sükosim process has been used primarily to supply heavy-duty components for automotive customers, including Daimler-Chrysler, BMW, and the Audi Group. Textron is exploring new applications for its Sükosim system in off-road, heavy manufacturing, and appliance areas, said Scott Nelson, director of product management of engineered products. The focus is on load-bearing parts and high volumes, he said.

According to Textron, its Sükosim system can more than double metal wall thickness in selected areas to produce components that will withstand high stress loads. In Europe, the process has been used to provide automotive chassis system components and load supporting assemblies. Other applications include seat anchor plates, engine mounts, tow hooks, and floating fasteners.

"If you take this material and create a shape that is unfriendly, it has a tendency to fail or split. We are able to get over that obstacle," Nelson said. "Through the tooling pressures, you are forming the metal and pushing it in the areas that you want it to be in."

Textron's Sükosim tooling selectively thickens the areas where more strength is needed, producing lighter and stronger load bearing parts (top photo).

Nelson said cold forming gives the parts structural integrity. Textron claims the finished parts have no corrosion points and no need for heat treating, which can lead to hydrogen embrittlement. Thicker walls also allow redrilling, retapping, and rethreading.

The process competes with machining, forging, and casting. For the most part, Textron is forming parts of low carbon steel because of its better formability, Nelson said. It is also pressing parts of higher carbon steel for specialized applications, he added.

Mercedes-Benz has been using fastener parts formed on the Sükosim press for 20 years, and today uses it for components in all of its passenger car models. According to Rodolfo Schöneburg, director of safety, NVH, and durability for Mercedes-Benz, fasteners formed on the Sükosim press include mountings for door hinges, seats, and seatbelts, and powertrain parts, including engine and transmission mounts.

According to Schöneburg, advantages include part reduction, elimination of weld seams, and weight savings of about 10 to 15 percent. For example, the rear transmission mounting, shaped by the Sükosim system, combined six components into a single bracket.

Mercedes is using the Sükosim process to form low carbon steel parts with a yield strength of up to 340 megapascals. Mercedes is also looking into the possibility of using the Sükosim system to form an aluminum part. Schöneburg has worked with Textron Fastening Systems on relatively large and complex parts.

Andy Osborn, account manager for Müller Weingarten, said the new 1,000-ton press would have a die area of about 178 inches by 48 inches. Textron said that can handle 20 to 45 die stations, depending on product size.