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Perfectly balanced excavators

At thyssenkrupp System Engineering located in Wadern-Lockweiler, 130 employees make tools and produce small runs of stamped parts for the automotive industry, as well as for the Group’s own research projects such as InCar®plus. Prototype parts are also produced on site.

The employees share decades of experience in the automotive sector, and for a few years now, they have also been active in areas such as agricultural technology, construction machinery, and sanitary installations. “The customers from these new areas know to appreciate our expertise from the automotive industry. A lot of confidence is placed in us,” says Team Manager Volker Grünewald.

Liebherr has been a customer since 2006. The company was looking for a development partner to design steel-made counterweights for excavators. Previously, Liebherr had been making its counterweights from gray cast iron. There were two main reasons that made Liebherr reconsider: costs and design. At the time, both steel and cast iron prices were rising dramatically. Also, the rough cast iron didn’t provide a smooth enough surface

Heavy shells: After deep drawing, the hollow shell is lifted using a special handling tool.

The top supplier is part of the group

The project team put together an initial order to attract a suitable supplier. Because of the plate dimensions required, this wasn’t going to be easy. Faced with needing to deliver a width of around 1,925 millimeters, most suppliers simply had to pass. In the end, the solution was to stay in the family – and turn to thyssenkrupp Steel Europe.

For production, the prototype shop uses its heaviest press, which has 2,000 metric tons of slide force. This is entirely necessary, as the plates for Liebherr are three millimeters thick and require immense forces to form them. By comparison, most of the plates used in the automotive industry only have a thickness of 0.6 to 2 millimeters. In addition, an enormous draw depth of up to 450 millimeters is required. “We gradually optimized the process and equipped the production area with the necessary handling tools. This way, we were able to reduce production costs by around 60 percent,” says Grünewald.

Recommending materials for easier metal forming is part and parcel of the advice provided by ThyssenKrupp Steel Europe. “We work together very closely with our Technical Customer Support team,” says Meike Giesbers, who is part of the steel producer’s sales team and looks after EU construction projects.

A weighty match: Volker Grünewald, Meike Giesbers, Martin Metzing, Peter Weiter (left to right).

Concrete and scrap metal hold the balance

Up to seven parts are drawn per hour and then cut using a 3D laser. While the plate weighs a massive 160 kilograms to start out with, it slims down to 100-110 kilograms after processing.

Yet, how is this weight going to secure an excavator with a service weight of up to 34,750 kilograms? The answer: The actual weight is added later on. The shells are assembled into a frame, fitted with a locking plate, and then filled with concrete and solid scrap. On completion, the counterweights weigh between 4.5 and 8 metric tons.

So far, thyssenkrupp System Engineering has developed and manufactured tools for nine of Liebherr’s model ranges. All of the excavators from these ranges, which are exported from Europe to everywhere in the world, are fitted with counterweight shells made in Lockweiler with sheet steel from Duisburg.

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