Cube67 fieldbus system: efficient wiring in complex machines

Transnova Ruf Verpackungs- und Palettiertechnik GmbH in Southern Germany is a successful packaging machinery company. About 250 employees design and produce turnkey machines and systems for secondary and end-of-line packaging. These systems pack products for shipping and distribution: single units are put into a box, or prepared in shelf-ready packaging; then the boxes are stacked on pallets. This requires a multi-stage packaging process; therefore, the engineers have to design and implement comprehensive and efficient systems that are able to link a series of consecutive processes. Since the mid-1990s, Transnova Ruf has been using robots in many applications, making the automation level very high.

Transnova Ruf does not produce "ready-made' machines for their customers. The company uses a modular approach where the individual functions are split into modules that can be assembled, as needed depending on the application. Michael Ruf, TR executive board member explains: "This gives us room for a wide variety of solutions." It also enables Transnova Ruf to meet the complex needs of their customers.

This approach also has another important advantage - it makes it possible to develop a winning system even under less than ideal conditions, such as installing a packaging machine in a small hall with many corners. The modules are designed as virtual templates with defined hardware and software components, which significantly reduces the engineering efforts. Transnova Ruf buys the components such as inspection systems, labelling devices or printers and integrates them into the machines.

Transnova Ruf produces not only small and compact systems, like "Case Packers' in their production halls; they also manufacture large, comprehensive systems with dimensions of up to 70 or 80m. A machine of this size has to be very modular not only for installation but also for transportation since that usually requires several trucks. As a result, decentralisation principles are given priority when it comes to the electrical installation of the systems, already in the early planning stages.

Hermann Schindler, who is responsible for the hardware planning, says: "We want to keep the installation lean. We don't want to have to route cables 50 or 100m into the cabinet." As a result, Transnova Ruf moved the frequency converters, which are quite numerous in a packaging system, from the cabinet into the field.

Autonomous system

Transnova Ruf is currently working on the logistics for a new production plant for a Swiss pharmaceutical company. Medical products are packed in small boxes that are then are conveyed on any one of 10 production lines via supply routes to make a round trip. From there they are transported to a lower level with spiral conveyers and then routed via switches to branch terminal lines. Two robots place the packages on pallets that are then carted with a linear carriage. The filled pallets are shrink wrapped before undergoing a contour check and receiving an information label. At the end of the process, the finished pallets are transported to the high-rack warehouse. The system operates by itself; Hermann Schindler explains: "Once every four hours it's necessary for a worker to replenish the film at the wrapping unit."

A large number of sensors and valves are integrated into this system. The data matrix codes printed on the primary packaging help to bring the boxes into the system at the right time and transport them to the right packaging station.

Transnova Ruf uses Murrelektronik's Cube67 fieldbus system as the backbone of the system's electrical installation. Since the fieldbus modules are connected with pluggable cables, Transnova Ruf's engineers along with Mr Schindler were able to put together a very flexible system that can be quickly assembled and disassembled as needed. Furthermore, the system is easily expandable. It does not require a lot of modifications from the electro-technical point of view. Often another Cube67 module can be integrated simply by connecting it to nearby module with a Murrelektronik hybrid (data and power) cable. The double-ended hybrid cables also lower the risk of wiring errors.

15 Cube67 ProfiNet bus nodes are installed in this system. The modules collect information from the sensors (mainly light curtains that detect the position of the product) and transfer the signals to the valves. The fieldbus system is responsible for about 70 drives in this installation. These SEW motors, located at various positions along the conveyor line, are equipped with integrated frequency converters. Hermann Schindler says: "This solution doesn't require any switch boxes and terminal boxes in the field, where the space is already confined." Using Murrelektronik's Movimot function module, Transnova Ruf connects a component for the Cube67 system that makes these motors easy to connect.

Because each port on a Cube67 module can handle two signals, Transnova Ruf's engineers use T-couplers to split the signals in some applications. In these cases the T-couplers connect M8 cables. To connect the data transfer unit that sends information from the palletising unit to the high-rack warehouse, Transnova Ruf's engineers use a Cube67 valve module with 16 contacts for the exchange of digital signals.

By implementing Cube67, Transnova Ruf achieves a practical and versatile installation concept. It fits into the new packaging system and, due to its modular design, it is a practical option that offers the potential for future expansions.

For more information about Murrelektronik's Cube67 fieldbus system please go to www.murrelektronik.co.uk.