By Brad F. Kuvin, Editor
With speed increases to 50 percent and positional precision down to the hundredths of a millimeter, hydraulic-press manufacturers are leading metalforming companies down new paths to productivity and profitability.
Servo-hydraulic technology appearing in newer hydraulic presses is rapidly convincing metalformers that now is the time to retire aging presses and bring in new models. Further, control-system updates from manufacturers of hydraulic presses deliver not only improved motion and force control, for faster and more accurate forming than ever before, but also the data-logging capability that remains a top priority among metalformers and their customers.
Lastly, modularity and flexibility inherent with hydraulic presses have spurred a whole new metalforming process-hot or warm forming-which has caught fire, literally, in the automotive industry.
Form it While it's Hot
"Hot forming is a trend in the automobile industry," says Peter Neubert of Muller Weingarten, a project manager for the construction of the firm's first hot-forming hydraulic press. The basic characteristics of hydraulic presses-variable slide speeds, adjustable pressure dwell times and easily adjustable tonnage-make the machines ideal for hot forming. Sheet steel is heated to approximately 1700 F and then formed in water-cooled dies that remain closed at bottom dead center for 8 to 10 sec. after forming. The process, originally developed for aluminum alloys, requires in some cases only one-third the press tonnage compared to cold forming. It hardens steel workpiece material to obtain twice to three times the strength of conventional parts, says Neubert. Typical automotive parts formed this way include A and B pillars and the frame tunnel. Click to Enlarge |
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| Muller Weingarten recently installed this hot-forming hydraulic-press line at Eagle Bend Mfg., a Magna Group company in Clinton, TN. The line, 165 ft. long, includes an oven to heat the blanks, and an 800-ton press that forms at speeds to 20 in./sec. |
Muller Weingarten recently has installed a hot-forming hydraulic-press line at Eagle Bend Manufacturing, a Magna Group company in Clinton, TN. The line, 165 ft. long, includes an oven to heat the blanks, and an 800-ton press that forms at speeds to 20 in./sec. Its success, after just a few months' time, led the firm to order a second identical line.
Schuler has had similar success moving hydraulic presses into automotive production for performing hot forming, and says that its customers typically start out with blanks of steel with initial tensile strength of 500 to 700 MPa and, after hot forming and cooling in the die, end up with parts strengthened to as high as 1300 to 1600 MPa. Schuler has delivered several hot-forming lines to automotive OEMs and their suppliers, primarily for production of safety-related parts such as side-impact supports, B-pillars, panel rockers, roof rails and floor-support elements. Six Schuler hot-forming lines are at work at the Volkswagen plant in Kassel, Germany, supplying components for the VW Passat.
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| One of six Schuler hot-forming lines at work at the Volkswagen plant in Kassel, Germany. |
One critical variable to the success of hot forming is forming speed, as the preheated blank must be formed before it cools any more than 100 to 150 deg. And an enabler of higher forming speeds is expanded application of servo-controlled axes, a recent technology development that most if not all builders of hydraulic presses are touting. AP&T is one such press builder.
"Servo control results in rapid forming, and provides high precision," says Mikael Karlsson, a project manager for the press builder. He boasts of positional precision down to the hundredths of a millimeter.
