Servo-Electric Pump Drive Optimizes Hydraulic
German hydraulic-press builder Lasco Umformtechnik GmbH introduces a hydraulic pump directly coupled with a servomotor as an energy-efficient solution to “provide substantial energy savings for companies operating our presses,” says Harald Barnickel, the firm’s head of electrical engineering. At the core of the drive package is a Simotics 1PH8 servomotor from Siemens, which directly drives the hydraulic pump. With a response time of 250 µs, up to 256 axes can be synchronized and precise axis motion and curve profiles executed.
Plunger speed is controlled by motor speed and thus by the volumetric flow rate of the pump. Four axial reciprocating pumps, with a fixed displacement per revolution, are connected simultaneously for a maximum pressure of 250 bar, to supply the pressure line for the press stroke of the plunger. Three additional pumps are responsible for the return stroke of the press plunger.
The press’s hydraulic oil tank holds 9000 l, and because of the high flow rate of 16,000 l/min., filling valves are used for the fast downward motion of the plunger. The servo pumps provide the required flow rate for the actual pressing operation, with a speed of up to 100 mm/s.
Previously, high-precision control valves with zero overlap were required to obtain precise traversing profiles. Now, this function is handled by the motion-control system in conjunction with the servo pumps, which allows the valve systems in the press to be reduced by as much as 40 percent. The end result is a notable improvement in energy efficiency. The energy-saving effect is particularly apparent, says Barnickel, during the drawing operation, when drawing pressure is provided by a pump equipped with a servomotor with the motor of the die cushion pump operating as a generator.
Although the Simotion controller has been optimized for motion-control applications, it also can control the complete system. However, Lasco separates the various press tasks and uses a separate PLC for system control. The development of servo technology for large hydraulic presses, based on the Simotion motion-control system, also is suitable for modernization and retrofit projects.Lasco USA: 734/241 0094; www.lascousa.com
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