Harmonious human-machine interaction

The historic Berlin Palace and its reconstruction are integral parts of German history. The rebuilding of the sandstone façade, including the production of three portals and an elaborate coat of arms cartouche, tells a special story. The team of Schubert Steinmetz- und Steinbildhauer from Dresden carried out this demanding and arduous work, actively supported by a robot and electric spindles from HSD Mechatronics.

The craftsmanship, artistic skills and expert knowledge of company founder and manager Sven Schubert and his team of 25 were particularly in demand when it came to the fine details. A robust robot assisted them during their hard work with a lot of dust and sweat. The heart of this machine tool comes from HSD Mechatronics: hard-wearing and reliable electric spindles that withstand even extremely aggressive treatment with contaminated cooling water.

The quality of these spindles is the result of extensive expertise: the company based in one of the most beautiful places in Italy has been developing, manufacturing and selling electric spindles, two-axis milling heads and technologically advanced components for the machining of metal, composite alloys and wood for over 30 years. This experience is reflected in the worldwide distribution of tools from Gradara, Italy. “Many renowned machine manufacturers use HSD spindles. We are an important supplier for our partners, as the motor spindle or milling head is always the heart and most important component of any machine tool.” As HSD area sales manager, Ferdinand Dannenmann knows about the importance of durable and functional products for lasting success and customer satisfaction.

With a light touch

Customers benefit from the mechanical engineering background and the user-oriented way of thinking of the HSD manager: “When using electric spindles in combination with a robot, it is always important to consider the size of the robot. This determines the additional weight that can be attached to the robot’s arms. In practice, the most important thing for our customers is how this payload – in this case a motor spindle – can be picked up quickly and easily for changing. This means that the adapter plates, the connector solutions, the coupling of hoses and cables must be correspondingly reliable and easy to handle.” This not only sounds promising to Sven Schubert, it also makes his and his team's work considerably easier – resulting in high quality of their work.

Over three decades of experience

The master stonemason and stone sculptor can draw on a wealth of experience. “We reconstruct historical buildings, do typical stonemasonry work and carve stone. We might work on cornices, façades or sculptures.” His company has been working in this field since 1990; and Schubert has actively and knowledgeably contributed to the success of several symbolic and culturally significant buildings throughout Germany. A prominent order came from the German capital, for the reconstruction of the Berlin Palace: the stone sculptors made the largest single sculpture in multiple parts and chiselled decorative elements in sandstone for the palace façade, altogether three thousand pieces such as eagles, putti, flower festoons and column capitals.

“A big job, a very big one. And it made us determine to get a robot. By now, we have been working with it for 13 or 14 years. It takes the hard work off our hands, the sweaty and dust-intensive jobs, so we can concentrate on the finer points.” Formerly a backyard workshop, the company now has modern machinery and has been embracing modern production methods for several years.

Cut in stone

At the beginning of each project there is a rough block of stone. And a small clay model, which the stonemasons scan to create a virtual 3-D copy. They can then create toolpaths for different milling bodies, depending on how accurate the figure is to be. Then the robot is released on the stone block and works through the programs. “In stone processing, a lot of the work is done with cooling water. This cooling water is contaminated with abrasive material from the stonework and is therefore very aggressive.”

The heart of the machine

“Schubert uses our ES796 series. All external materials and components that come into contact with cooling water are made entirely of stainless steel; this makes the spindles immune to corrosion.” Dannenmann knows about the various benefits of HSD spindles. “Another advantage is the special design of the rotary union. Since this is an overpressure system, the excess pressure can drain off to the side, so to say. The spindle in our Dresden operation has a maximum power of 18 kW with about 40 Nm and a maximum speed of 12,000 revolutions. This is absolutely sufficient for stone processing, as we tend to work in the low-speed range.”

The final touch

As a graduate geologist, Edgard Scheidewig has a profound understanding of the composition and structure of minerals. As a stonemason, he has learned how to work with natural stone from scratch. He gives the workpiece the finishing touches after the robot has prepared it. “Based on the work sheet, we check carefully which corners still need to be carved deeper and how much. Naturally, this is a manual job.”

Unfortunately, not many people have this ability anymore nowadays. Sven Schubert is glad that his employees are also artists, historians, planners and 3-D digitization professionals. He employs stone sculptors, restorers and geologists. In total, there are between 15 and 25 employees, depending on the order situation. And while the past plays an important role for the company, Schubert has his sights on the future and is committed to promoting young talent: over the years, the master craftsman has trained several apprentices.