When companies from the automation industry submit an order to Murrelektronik, the Oppenweiler Logistics Center operates like clockwork. The ordered products are transported by conveyor belts to the picking and packing stations, and they are packed and on their way to their destination in no time at all.

To keep logistics operating at full speed, all picking and packing stations are fully staffed. When one employee goes on break, a coworker takes over the tasks immediately. When packaging material is about to run out, an internal logistics specialist intervenes so that bottlenecks do not occur.

A team managed by Oliver Behnke, Department Head of the Murrelektronik Logistics Center, undertook the task of simplifying this system. A decision was made to install an entire row of Modlight70 signal towers that are easily visible. Since then, employees in the operations area and colleagues in the control room of the Logistics Center can see at a glance whether all processes are running on schedule.

Employees at the picking and packing stations operate the lamps from their workstation by remote control. When the green LED light is illuminated, everything is running well. The yellow light indicates that an employee is taking a break, so a relief person can be ready to step in. Blue stands for a packaging material bottleneck; red means an interruption. The signals are unambiguous — nothing has to be done on call anymore.

The large Logistics Center proved to be a challenge, which became evident in an early phase of planning. Relying on radio signals to be clearly transmitted over long distances or even through walls seemed impractical to Oliver Behnke’s team. That’s why the team decided to transmit the radio signals digitally through cables using a decentralized installation solution based on the Cube fieldbus system.

The receivers were in control cabinets at multiple locations within the Logistics Center. These receivers control the inputs of the Cube20 IP20 fieldbus module. These input modules communicate with the PLC, which processes the signals and sends them to the Cube67 fieldbus system in the field, which controls the Modlight70 signal towers.

The use of Cube20 in the control cabinet is a cost-efficient solution: instead of many individual I/O cards, only one module has to be mounted on the DIN rail. The high packing density makes this possible. “Specifically, we had to install only one module in each control cabinet,” reports Oliver Behnke. In practice, single-channel diagnostics directly on the module has proven to be advantageous. “If there is an error anywhere in the wiring, the LED will light up at the affected port, and we can fix the error quickly without having to constantly look for the error.”

Practical modules with a direct Modlight signal connection are used to connect the actuators in the Cube67 system. These Cube cable modules have a 1.5-meter long connecting cable; the 8-pin M12 connector is connected directly to the signal tower. The individual connection modules are in turn connected to a system line that carries the signal as well as the power. “With this system, we do not need a separate power supply. This makes installation quick and easy.”

The Modlight70 signal towers can be assembled in a modular fashion from a connection element and several colored LED modules with a 70 mm diameter through a bayonet locking system. “In the Logistics Center, we assigned colors to certain functions which is why we use the signal towers in the identical configuration,” explains Oliver Behnke. He values the energy-saving LED technology, the long service life, and the maintenance-free modules.