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Brick on Brick

KUKA Robots help to reconstruct baroque façades of Berlin City Palace

21 September 2015

© Berlin Palace–Humboldtforum Foundation / Architect: Franco Stella with FS HUF PG
They provide valuable support with their precision and speed: KUKA robots are helping with the reconstruction of the façades of the Berlin City Palace. KUKA Robots carry out pre-milling of the sandstone. Stonemasons and sculptors then perform detailed work on these pre-milled raw parts. The object of the exercise is to restore the north and south façades of the Berlin City Palace to their former glory using around 8000 tonnes of sandstone.

The decision to rebuild

Der The monumental building in the former East German part of the city was severely dam-aged during the war and was demolished in 1950. It is being rebuilt to plans by the Italian architect Franco Stella. In 2007, the German parliament took the decision to rebuild the Berlin City Palace at the end of the prestigious “Unter den Linden” boulevard. There was a major challenge: after demolition, the stones used for the original building were dis-persed over several major disposal sites and could no longer be found under the rubble caused by the wartime bombing. What did remain, however, were thousands of construction files dating back to renovation work carried out since the 18th century. It is this archive material that is now serving as the basis for the reconstruction. It is the final baroque extension, complete with its decorative façade ornamentation, that is being reconstructed. This requires replica sculptures, faithful to the original, in natural stone, which is precisely where Bamberger Natursteinwerk Hermann Graser and KUKA come in.

The reconstruction process

How does one go about reconstructing an entire palace, with a natural stone façade that is true to the original, and with completion scheduled for 2018? What is needed are exact drawings, good 1:1 models of all sculptural façade elements and an extremely large quantity of high-quality sandstone. It also takes the know-how of experienced companies with a high performance capacity who are able, on the one hand, to work manually with natural stone, while at the same time having a comprehensive grasp of the intelligent use of high-precision 3D images and contemporary CAD/CAM and robotic technologies. In order to be able to manufacture sculptural elements from natural stone, the sculptor first has to prepare a plaster model; in a second step, this plaster model is transferred to a self-contained 3D model by means of non-contact and non-destructive scanning techniques. In a third step, this model serves as a template for the robot as it produces a 1:1 raw part in natural stone for manual finishing work by masons and sculptors to ensure that it corresponds to the historic original. When it comes to architectural sculpture, no two parts should look exactly alike. The individual finished parts are finally taken, together with a laying plan, to the construction site where the Bamberg-based masons and others are building the baroque façades.

Three KUKA robots in operation at Bamberger Natursteinwerk

As a test partner for KUKA Robotics, Bamberger Natursteinwerk Hermann Graser GmbH put Germany’s first stoneworking robot into operation in 2008. Three KR 500 L480 MT robots equipped with the KUKA KR C4 controller work together with 25 stonemasons and sculptors, and not just for this major contract. In the bid for tenders for the reconstruction of Berlin City Palace, Bamberger Natursteinwerk Hermann Graser was awarded contracts for the courtyard façades on the north and south sides, as well as Portals I and V providing access to the Schlüter Courtyard. For the reconstruction, sandstone for approximately 2,400 m³ of high-quality masonry work, such as window surrounds, cornices and columns, as well as around 600 complete sculptures, will be required in a short space of time from various different quarries.