In the most basic sense, mechanical presses, like the people on the bus in the old song, go up and down. But the advent of complex, larger tooling and the need for stampers, especially in the contract realm, to be flexible, call for changes in the ways presses are designed, built and delivered. Nowadays, as press manufacturers will tell you, the process of mechanical-press construction is more customer-driven than ever. Manufacturers add flexibility to presses at a cost that withstands the quality and price requirements demanded by stampers.

If you haven't looked closely at mechanical-press offerings in the past five to 10 years, sure, they still go up and down, but a whole lot else has changed.

Frames Showing Their Mettle

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Transfer presses such as this employ large front-to-back designs to handle larger parts.

Time was when cast iron formed the majority of the main press frame. Then, the only way to bolster rigidity was to throw more cast iron at it. Not any more. Today, press frames include fabricated steel plate in a larger percentage than ever before, especially in straightside presses, while many gapframe machines still hold a cast-iron frame.

"When cast iron was cheap, it was easy to throw more on," recalls David Stone, stamping consultant for Amada America Inc., Buena Park, CA, which in the past couple of years has rolled out its gap-frame and straightside models (to 500 tons) to the North American market." But no one really knew what effect throwing more cast iron on had. Also, the casting patterns for frames are very expensive, so once you design one you had better offer it for a long time."

Cast iron frames do offer some advantages, however.

"They can be shipped in one piece and require less machining and fabricating to produce," notes John Matthews, vice president of sales and marketing for Enprotech Mechanical Services, Inc., Lansing, MI. The company recently purchased Danly and Verson assets, two big names in American press-building history. Today, Enprotech offers repair and rebuild services and has entered the new press business, supplying straightsides through the Verson acquisition. "But, of course, cast-iron frames can't be taken apart and there are some machining challenges," Matthews continues, noting that one-piece construction is most viable for straightsides in the 300-ton-or-less range.

The advent of computer technology, to test frame designs for rigidity and reliability, has made steel plate more accepted for frame construction. In some cases, stampers still specify more cast iron due to its dampening characteristics, which are higher than that of plate steel and help decrease vibration.

"Today, we conduct a finite-element analysis (FEA) on the designs of all stressed frame components," says Denny Boerger, national sales manager for Aida-Dayton Technologies Corp., Dayton, OH, describing the efforts of his company and the press-manufacturing industry as a whole. "Then we try to redistribute the material so that it is most effectively used. The result is a stronger machine with, in some cases, less material in it."

Others agree, noting that the technology helps hold down press costs to stampers.

"Because of CAD and FEA, manufacturers, for example, can use 11⁄8-in.-thick plate for certain areas of the frame whereas before they used 1.5-in.-thick plate," explains Tony Mase, general sales manager for The Heim Group, Chicago, IL, which provides gap-frame and straightside models for general-purpose work.

Fitting those plates together correctly also has been addressed, with an eye toward enhancing press life.

"In the past, manufacturers would weld based off the stress but as stampers increasingly use higher-strength stock, manufacturers are starting to weld for fatigue as well," notes Pat Ontrop, director of contract market segment for Minster Machine Co., Minster, OH, which builds gap-frame presses and straightsides to 1600 tons.

Bigger and Stronger

Responding to stamper demands, manufacturers across the board also are providing presses with ever-increasing bed areas, oversized windows and decreased deflection characteristics.

The use of more complex tooling and wider materials has brought presses with ever-increasing bed areas.

"There's been a shift in the size of parts produced, in transfer presses for example, so we must have exceedingly large front-to-back designs," says Bob Budz, director of automotive sales for Fagor Arrasate, in Florence, KY. With U.S. operations centered in Bensonville, IL, this Spain-based company has operated in North America with its own staff for two years, supplying turnkey transfer-press systems with large straightside presses.

Dies are larger and do more today than ever before, as wider material finds its way into stamping presses. Manufacturers have built larger work areas into their offerings to adapt to this trend and accommodate transfer, lube and other equipment.