Together with its customer, Maschinenfabrik Herkules,Baumüller has converted an EDT (Electrical Discharge Texturing) machine to decentralized drive technology. The changeover has increased the efficiency of the machine, reduced the amount of cabling and the footprint, improved serviceability and simplified installation.

The Herkules EDT machine uses spark extrusion to process the surface of steel rollers, which in turn are used for sheet metal processing. The structure of the roller is transferred to the sheet metal and thus improves its properties during painting and deep drawing. Texturing the surface also extends the service life of the rollers. Herkules texturing machines are characterized by high performance, productivity and availability and meet high standards of accuracy. The machines cover a wide range of roller sizes and diameters.

Structure in the surface

For processing, the roller lies in a bath of dielectric, usually non-conductive oil. It is inserted into a headstock and set in rotary motion around the longitudinal axis by a DA1 main drive with b-maXX-5100 mains inverter and b-maXX-5300 axis units from Baumüller. Servomotors move the electrodes towards the roller. Generators produce a voltage at the electrodes, which creates an electric field between the negative pole on the roller and the positive pole on the electrode. If the distance is correct, a defined discharge occurs. The resulting electric arc burns a microscopically small crater into the surface. The structure can be precisely programmed so that a homogeneous surface quality is achieved. The permissible tolerances during processing are very tight. The distance between the roller and the individual electrodes is crucial for a perfect surface; the distance must be constantly readjusted. This is where the decentralized Baumüller b maXX 2500 drives are used in the latest generation of EDT machines. By minimally readjusting the position of the electrodes, the drives can compensate for run-out tolerances of the roller caused by the tension.

The decentralized drives

Decentralized drive concepts shift the control and power electronics from the control cabinet to the drive. Optimized cooling concepts and innovations in power components have paved the way for decentralized drive technology. This plays into the hands of the trend towards machine modularization. It also improves efficiency in system construction, reduces cabling costs and increases compactness.

The decentralized drives with hybrid connection technology. © Baumüller

The most important requirement for the drives that move the electrodes to the roller was positioning accuracy. Depending on the expansion stage, between 27 and 50 decentralized drives from the b maXX 2500 series are installed in the Herkules EDT machine for positioning the electrodes. These are highly dynamic servomotors with directly mounted controllers. Baumüller combines its b maXX 3300 servo drives with the DSD2 servo motors to create a compact positioning drive with protection class up to IP65 and various connection options such as plug connectors for single cables, hybrid cables and connection cables.

The idea of converting the texturing machine from centralized to decentralized drive technology was initiated by Baumüller. An important advantage, considering the large number of up to 50 drives, is the reduced wiring effort. The changeover has eliminated numerous annoying cable ducts, and the wiring effort has been significantly reduced, particularly through the use of the hybrid connector, which combines DC link connection, electronics supply and fieldbus. Service-friendliness has also improved thanks to the use of the hybrid connector. Drive units can be replaced quickly. By relocating the inverters from the control cabinet directly to the motor, external main motor connection and encoder cables are no longer required. This means that EMC measures can be implemented with significantly less effort. The combination of decentralized drive technology with a power supply unit with integrated safe DC link disconnection makes the STO safety function easy to implement. Another important advantage is the improved efficiency in the planning and construction of the Herkules machine. One reason for this is the air conditioning of the control cabinet, which is now smaller. The smaller control cabinet size has also led to an overall reduction in the machine's footprint.

Conversion without new construction

The conversion of the system to decentralized drive technology was possible without mechanical redesign or new construction. The flange and shaft dimensions of the drives remained the same, and no adjustments had to be made in terms of fieldbus communication or connection to the machine control system. The operating software for the drives is still the tried-and-tested ProDrive; no training in new software was necessary. "Thanks to the compatibility of the decentralized drives with the other Baumüller servo drives, the changeover was uncomplicated and quick to implement," praises Harald Kraft, Senior Director Electrics at Herkules.

The partnership between drive and automation specialist Baumüller and Maschinenfabrik Herkules goes back many years. Herkules is the world's leading specialist for roller processing machines. Herkules roll grinding and turning machines are used wherever high-performance machine tools are required for high-precision machining of workpieces. With over 100 years of history, the family-owned company stands for tradition paired with innovation and the continuous optimization of its machine tools.

Partnership of family businesses

Herkules particularly appreciates the fact that Baumüller relies on the Customized Standard for its products. This means that products can be designed flexibly to a certain extent and there is a wide range of options. This benefits the machine factory's individual machines. "Baumüller is also a medium-sized, family-run company, which fits in well with Maschinenfabrik Herkules, which is also family-run," says Harald Kraft. As a medium-sized company, Baumüller also has service centers around the world that are available to support end customers.

Susanne Reinhard, Press and Public Relations, Baumüller