When Trench Germany in Bamberg, a subsidiary of Siemens Energy, moves the insulators it manufactures itself, heavy equipment is required. The largest ones are more than four and a half meters high and weigh several hundred kilograms despite being made of lightweight GRP composite material. The tube of such an insulator is coated with a ribbed silicone structure, which is applied by injection molding. Burrs remain on the silicone shell, which have to be removed for reasons of functional safety. Until now, this was a laborious process that kept the workers busy for hours: they used a small hand-held grinder to remove the burrs from each individual silicone rib at the seams.

Automation with industrial robots

Trench Germany decided to automate this complex process as far as possible in order to increase production capacity while maintaining the same number of employees. However, a corresponding system did not yet exist. In summer 2020, Trench therefore commissioned Potzi in Trainau near Lichtenfels to build a special machine. Potzi develops and manufactures customized systems, and the specialists also provide the software and commissioning themselves. At the heart of this application is an industrial robot with six degrees of freedom, which guides the grinding device instead of the worker and also directly extracts the silicone chips using a narrow nozzle. The insulators to be cleaned are rotated slowly in order to achieve the best result. The robot moves precisely along the insulator.

The rotary drive for the insulators with energy chains. © SEW-Eurodrive

The requirements for the deburring station at Trench were particularly high: the system has to cope with overall lengths of between 700 and 4,500 mm and diameters of 158 to 440 mm. The corresponding workpiece weights are between 22 and 306 kg. On the one hand, the special machine has to handle the deburring process automatically, but on the other hand it also has to enable manual post-processing, for example to fill cavities. Blowholes are small holes and unwanted cavities created during the casting process. The deburring station is therefore operated alternately on both sides: While an insulator is still being processed automatically on one side, a worker is already putting the finishing touches to the silicone ribs on the other.

Drive technology for a wide range of requirements

"We found drives that can cover such a wide range of requirements at SEW-Eurodrive," reports Stefan Götz, Technical Manager at Potzi. Two DRN series asynchronous motors from SEW-Eurodrive with Spiroplan right-angle gearboxes are used to rotate the isolator on each side of the system. They are operated as a group drive, with one of the two motors reporting back the position using a rotary encoder. "The second application is height adjustment," explains Daniel Bautz, head of the Nuremberg technical office at SEW-Eurodrive. Here too, two drives are installed on each side of the system, in this case synchronous servomotors from SEW-Eurodrive's CMP series. Like the drives for the rotary movement, they are equipped with Spiroplan angular gearboxes and absolute encoders. All drives are controlled by Movidrive modular frequency inverters: Two single-axis modules from the Movi-C modular automation system supply the rotary drives in group mode, while two double-axis modules control the servos for height adjustment independently of each other.