Based on the "Bridge the Gap" principle, Stöber has launched an energy-efficient solution on the market with the lean motor and presented it for the first time at SPS IPC Drives in Nuremberg 2017: The consistently encoderless drive is significantly lighter and smaller than an asynchronous drive and cheaper and more robust than a servo drive while delivering the same performance. Speed and torque can be infinitely adjusted from standstill to maximum speed with full torque control. With an efficiency of up to 96 percent, the lean motor corresponds to efficiency level IE5. To achieve this, Stöber has combined the drive with the SC6 and SI6 controllers. The speed deviation is less than one percent and the positioning accuracy is plus/minus one degree.

"To produce the blanks for the new lean motor, we developed a fully automated assembly system consisting of three Scara robots and a rotary indexing table with five stations for the individual processing steps," explains Heiko Berner, Product Manager PLC at Stöber. Together with his colleague Heiko Bismarck, Product Trainer & Supporter, he was responsible for the complete automation. "To safely handle the 16 axes in total, we use our SI6 double-axis bayed drive controllers," reports Bismarck. "These only require a width of 40.5 centimetres in the control cabinet, including the PS6 supply module."

Low-backlash planetary or bevel gearboxes are used at all points where high precision and repeat accuracy are required. This applies in particular to the axes in the robots and in the rotary indexing table. They are controlled centrally via the MC6 motion controller. This is suitable for cycle-synchronous control via Ethercat and also handles the entire human-machine interface. All calculations for path planning and interpolation of the three robots are also performed centrally. "We have kept the interface as simple as possible for the application programmer," says Berner. "The programmer can position the robots directly via point-to-point (PtP) and - if necessary - use taught positions in the program sequence."

The SI6 double-axis bayed drive controllers require very little space in the control cabinet. © Rummager

The visualization integrated in the system can be used by the user directly at the machine for operation and information. Language switching is also included, as is user administration. The latter ensures that the employee can operate the machine in a user-friendly manner, with customized settings and intervention options on the integrated touch panel.

"Our Automation Control Suite AS6 development environment includes all the functions for motion control and programmable logic controllers contained in Codesys V3," explains Bismarck. "High-performance Drive&Motion libraries are available to us for program creation, with which the application can be supported with significantly reduced programming effort." In numerous application examples of the cost-neutral 30-day trial version of AS6, it is possible to see not only the implementation of format management but also how operating menus are structured or how comprehensive alarm management is structured. Format management is used in this system for a quick changeover of the blank format. The format-dependent parts of the machine to be changed can be visualized on the control system. The change must be acknowledged accordingly. At this point, it is conceivable to play a video or display PDF documentation on the motion controller if larger conversions are involved.

The lean motor from Stöber © Rummager

The machine consists of four stations. At the first, a four-axis scara robot places the blank on a holder. The robot then removes it from the rotary indexing table in its finished state. The machine is loaded and unloaded via two buffer sections consisting of conveyor belts. At the next station, a second robot places the correct number of additional blanks and positions them in station three for the next processing step. The third Scara robot applies a liquid mass at station four. The important thing here is that the quantity of material and the linear path must harmonize. This is the only way to ensure an optimum result, even with different circular blank sizes. To do this, the system carries out an automated measurement and corrects the path accordingly. In this process, a linear path is explicitly run, while at other points in the machine, the path planning automatically calculates the fastest connection between two points in space. as

The automated magnet assembly in the video.