30 n MACHINE BUILDING April 2026 www.drivesncontrols.com Digital twins ease the development of Swiss tram-washing system A new tram-washing system in Zurich's Oerlikon district is special in several ways. Instead of the usual two washing cars designed to clean tram surfaces – the new system uses four individually movable washing cars, resulting in thorough cleaning with short washing times and low energy usage. For BHB Waschanlagen, the German mechanical engineering company that designed and built the machine for Zurich’s public transport operator, Zürcher Verkehrsverbund, the challenging project also represented a milestone in its own digital transformation. It was the first time that it had used digital twins in combination with simpler low-code programming. This made it possible to plan the complex system with much less effort, and resulted in quicker commissioning than usual. BHB’s 20-person machine manufacturing team was supported by Atina, a Stuttgart-based engineering firm and software specialist. “Customer demands for flexible, networked and resource-efficiency systems are increasing, especially amid the skilled labour shortages,” says BHB managing director, Tobias Straub. “This means new digital concepts are required.” “We came into contact with Atina, which has provided us with significant support in our digitalisation efforts,” Straub reports. “This enabled us to use a digital twin and the new low-code programming solution for the first time in the Zurich project.” Atina's low-code programming language eliminates the need for hard-coded, line-by-line programming. Washing programs can be parameterised easily using Excel spreadsheets, even by people who lack programming expertise. This saves time, reduces errors, and facilitates subsequent revisions. And with only 200 lines of text, instead of 4,000, the programs are clearer and easier for service personnel to understand. The programs, created in Excel, can be transferred directly to control systems via a simple CSV export. In addition to the scripting language, BHB used a digital twin for the first time for the Zurich project. All of the washing system’s mechanical and electrical components are stored as functional 3D models and can be controlled by a real Mitsubishi PLC. Because the programs can be tested accurately by someone sitting at a desk, on-site commissioning is greatly accelerated and is almost error-free – an enormous economic advantage, especially on complex projects. However, digital twins and low-code programming alone would not have been enough to meet the customer’s needs. At the heart of the control system is Mitsubishi’s compact Melsec FX5U-64MR/DS PLC. In addition, Mitsubishi FR-E800 drives allow flexible motor control, cutting energy and water consumption, and helping to operate the plant economically. The BHB project could serve as a model for mid-sized machine-builders. Thanks to close cooperation with its partners, the company drove forward its digital transformation at the right time. The result is a machine that meets the demand for sustainability and efficiency, while showing how digital technologies can help mid-sized machine-builders to remain competitive and attractive to skilled workers. n A new washing machine that is used to clean trams in Zurich was developed and commissioned much faster than usual by using a combination of digital twins and low-code programming techniques. The programs are also clearer and easier for service personnel to understand. Four wash cars move along the sides of a tram as it is parked in the washing machine Digital twins allowed the tram-washing system to be tested at a desk, cutting commissioning times dramatically. The virtual model is controlled by a real PLC to ensure that the simulation is realistic.
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