At this steel mill, great force is applied with a delicate touch. The master computer sends all the data on the workpiece to the leveling system, which then sets parameters in regard to diameter, material and the required degree of accuracy. The electric motor for the pump drive starts up with a purr before a hydraulically powered ram presses the workpiece against two anvils. This is done so carefully that the remaining deviation is less than 0.1 mm at forces up to 25,000 kN. The large-scale leveling unit from MAE Götzen GmbH (Erkrath, Germany) is an entirely new generation of machinery in the tough steel mill setting. With a modern, multi-stage concept, the leveling system can be used for a multitude of products, from large steel rollers to delicate profiles. “Our development goal was to create a series of modularized units that would cover the entire range of needs for leveling long parts, from relatively low forces with manual charging to extremely powerful, fully automatic concepts,” explains Manfred Mitze, the chief executive of MAE Götzen.
To achieve these goals, the engineers at the leveling and joining specialists in Erkrath needed exactly the right drive. Mitze searched for a highly capable co-developer for the company’s patented drive concept that could partner in all the automation and provide motion control, electro-mechanical components and pneumatics. He chose Bosch Rexroth AG (Lohr am Main in Germany) to work hand-in-hand with MAE and design a complete drive system. This signiﬁcantly simpliﬁed the hydraulic conﬁguration.
At the heart of the system is a Sytronix variable-speed pump drive that uses an intelligent regulator and a servomotor to drive two adjustable axial piston pumps on a shaft. The drive positions the diﬀerential cylinder directly, without a control valve. Whenever the process requires only partial power, the speed drops to meet that need. In this way, the pump drive can reduce energy consumption by up to 80 percent when compared with a constant-velocity unit. In addition, mean noise emissions may fall as much as 20 decibels. There are other advantages as well. The hydraulic fluid hardly heats up at all, eliminating the oil cooler unit. The volume of hydraulic ﬂuid is reduced by about half compared to conventional designs. The pumps, driven with this degree of eﬃciency, move a diﬀerential cylinder inside a closed control loop at great precision that follows the specifications issued by the RICOS leveling measurement control, which was developed by MAE.
SET-UP WITHOUT DANGER
Located below the machine controls, the drive-based IndraMotion MLD logic system by Rexroth completes the control loop governing the cylinder position, force, and speed of the pump drive. “They built wide-ranging experience with hydraulics into their software,” notes Mitze. “The drive-based motion control eases the work for our process controls. Depending on the size of the machine, we can utilize hydraulic or electric drive solutions without additional eﬀort.” In its largest version, the leveling machine may involve up to 20 servo drives. Mitze is also highly satisﬁed in terms of machine safety. By integrating the Safety on Board concept into the drives, the operator can, with the guard door open, set up and load the machine without any risk at all.
The new large-scale leveling systems are already in operation in Europe, the U.S., and Asia.
Bosch Rexroth AG, Maria-Theresien-Str. 23, 97816 Lohr am Main, Germany, +49 (0) 9352-18 0, Fax: +49 (0) 9352-18 3972, www.boschrexroth.com.
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