Energy is everything in manufacturing, which forgers know as well as anyone. Energy must be available and affordable, but it also must be immediately accessible, reliable and manageable. And, the energy control and delivery functions must be efficient. All of these details matter just as much to manufacturing equipment designers and control engineers as to operators.
“Our new servo technology provides substantial energy savings for companies operating our presses,” according to Harald Barnickel, who heads the Electrical Engineering Department at Lasco Umformtechnik GmbH.
The builder of hydraulic forging presses and screw presses, as well as forging hammers, forging and cross wedge rolls, also has a line of automated hydraulic presses and related machines for producing sand-lime bricks.
“As a solution provider, we develop customized systems for optimized workpiece transport within the press as well as for feeding and removing workpieces,” Barnickel explained. Lasco emphasizes continuous improvement in its processes and technology, and the servo technology is that sort of technological milestone, as demonstrated by its implementation in a recently delivered deep-drawing press with a press force of 800 tons for up to 40 strokes per minute.
At the core of this solution — directly driving the hydraulic pump — is a Simotics 1PH8 servomotor, a product of Siemens Automation. This drive is controlled by the Sinamics S120 drive platform. A Simotion D445 motion control system handles the complete path, velocity, and position control of the axes.
With a response time of 250 µs, up to 256 axes can be synchronized quickly and precise axis motion and curve profiles are executed. “The initial applications have demonstrated that this type of servo technology provides outstanding results,” said Barnickel, noting the drive’s closed-loop control performance as well as its energy efficiency.
The challenge on the deep drawing press was to control the press force and press speed, based on a motion profile that could be set individually. The hydraulic force can be adjusted at the servomotor by means of the torque. The plunger speed is controlled by the motor speed and thus by the volumetric flow rate of the pump. Axial reciprocating pumps with a fixed displacement per revolution were used for the project described here.
Four such pump systems, connected simultaneously for a maximum pressure of 250 bar, supply the pressure line for the press stroke of the plunger; three additional pump systems are responsible for the return stroke of the press plunger. “The possibility of scaling, in other words adapting this kind of standard servo solution to the actual requirements, is another advantage of this new technology that certainly cannot be underestimated,” noted Barnickel.
The hydraulic oil tank of the deep drawing press holds about 2,377 gallons (9,000 liters). 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.