Efficiently producing complex shapesOstseestaal’s products are used not just in buildings but also in works of art. The sculptures at Expo Milan and the “Wings” sculpture by American architect Daniel Libeskind at the Siemens headquarters in Munich are clad with individually formed metal plates. The olive tree on the façade of the Doha Exhibition and Convention Center was also designed from individual parts that were specially produced by the company based in Stralsund, Germany.
Using an innovative, model-based, closed-loop control system to quickly and precisely form sheet metal
“We produce individual parts according to our clients’ requirements, which are very specific in terms of shape and surface quality. We were running up against technological as well as commercial limits with our existing metal-forming systems – which is why we initiated a research project with Hochschule Wismar and Hochschule Stralsund universities of applied sciences to help us efficiently form these complex geometries,” explains Harry Schellhorn. He heads the research project at Ostseestaal, where a multi-ram press and an innovative closed-loop control system will reduce machining time and improve the quality of the elements being produced.
In many cases, each individual metal piece is a unique specimen and therefore costly and time-consuming to form, says Schellhorn: “Until now, we’ve pressed the sheets into shape manually, with correspondingly long setup and machining times. The whole process takes from thirty minutes to an hour. The sheet material, which is usually aluminum or stainless steel, is in itself inhomogeneous, which means that the results of the pressing process are influenced by many parameters. That’s why automatic forming requires a more complex closed-loop control system than has existed so far.”
Innovation for 3D formingWith this research project, Ostseestaal and Hochschule Wismar are continuing a longstanding tradition of cooperation between industry and engineering sciences in Mecklenburg-Vorpommern: Wismar has been a site for applied engineering education for over 100 years.
The right team for efficient, automatic 3D forming of metal sheets
The research being conducted in Wismar also covers automation technology and mechatronics. The combination of industry expertise and development expertise was one of the main factors contributing to the successful creation of the new close-loop control system.
The Stralsund-based company Ostseestaal specializes in the manufacture of complex, three-dimensionally formed components. In recent years the company has established a reputation as an innovative and competitive partner for metalworking, with a focus on products for architecture, ship building, renewables, and industry. Innovation and tradition go hand in hand – including cooperation with Hochschule Wismar.
We need a flexible and efficient solution for the large number of individual shapes that we form from metal sheets.Harry Schellhorn, Project Manager, Ostseestaal GmbH & Co. KG
Automatic generation of complex closed-loop control functions
Because the solution is extremely compact, press operators can monitor and operate both the Leica measurement system and the press from a single device. SIMATIC Target 1500S automatically converts the control algorithm for the Fuzzy Control Toolbox from Simulink to a corresponding function block that loads and executes the functions from the control program.
At the heart of the solution is a SIMATIC IPC Panel PC on which both the Windows operating system and the SIMATIC S7-1500 software controller are installed. A SIMATIC ET200M system connects the analog and digital modules for controlling the press’s hydraulic rams, sensors, and hydraulic pumps and the measurement system with the controller. Using the Panel PC’s touch display, operators can simply specify the target values and view the status of each individual ram at a glance.
Without closed-loop control, the press’s hydraulic rams can be only positioned with centimeter accuracy. To achieve millimeter precision, Hochschule Wismar developed a special closed-loop control algorithm. Because the proportional valves of the hydraulic cylinders have a nonlinear rangeability, and the setpoint must be reached without overshoots, the team used a fuzzy controller. After the closed-loop controller had been generated and parametrized in Simulink, SIMATIC Target 1500S was used to load it into the TIA Portal engineering framework, where a function block was automatically generated that can be retrieved just like any other internal PLC function block.
Thanks to the SIMATIC controller and the fuzzy closed-loop controller, we can position the hydraulic rams with the necessary precision.Alexander Martens, research assistant, Hochschule Wismar
Integrated solution facilitates implementation both in the test system and in operations
Schellhorn is also convinced: “Without the development of the closed-loop control system in Simulink and its combination with SIMATIC Target 1500S, this level of quality and precision could never have been achieved.”
According to Dr. Olaf Hagendorf, project manager for Hochschule Wismar, the main benefit of SIMATIC Target 1500S for the project team was the automatic implementation of the controller design in the PLC. “The manual programming of a comparatively complex, closed-loop control algorithm like the one needed for the PLC for this application would require considerable effort – and there’s always the risk of error. With SIMATIC Target 1500S, we automatically generate the function block, which is guaranteed error-free. The time savings are tremendous.”
For Schellhorn, the results of the project were of primary importance. The hydraulic rams’ closed-loop control system operates according to Ostseestaal’s precise specifications, and the overall quality also meets expectations. However, he’s also already considering the possibility of using the press system in production – and this is where Ostseestaal stands to benefit from the solution’s SIMATIC platform: “Here we use SIMATIC controllers practically throughout, and thanks to SIMATIC Target 1500S, we can also implement new, more complex press control using the same technology.” According to Hagendorf, Hochschule Wismar will also continue to use SIMATIC Target 1500S. “We use SIMATIC for our work in automation technology and MATLAB and Simulink for our work in closed-loop control engineering. With SIMATIC Target 1500S, we can now strengthen the link between our two main areas of training, which will also improve quality in teaching.”
SIMATIC Target 1500S was absolutely essential for implementing our ideas and achieving Ostseestaal’s goals.Dr. Olaf Hagendorf, Project Manager, Hochschule Wismar