Efficient wiring for complex machines

The southern Germany based company, Transnova Ruf Verpackungs und Palettiertechnik GmbH (to give it its full title – TR from now on) is a successful packaging machinery manufacturer, employing around 250 people and producing turnkey machines and systems for secondary and end-of-line packaging operations.

TR’s machines pack products for shipping and distribution; single units are placed in a box or prepared in shelf-ready packaging, then the boxes are stacked on pallets. This requires a multi-stage packaging process, requiring efficient systems that are able to link a series of consecutive process actions. Since the mid-1990s, the company has been using robots in many applications, ensuring a high level of automation.

TR doesn't produce ‘ready-made’ machines for its customers; instead, the company divides individual machine functions into modules that can be assembled, as needed depending on the application. This approach enables TR to meet a wide range of customer requirements; it also gives the company another important advantage as machines can be designed to fit into any environment. 

Essentially, TR’s machine modules are designed as ‘virtual templates’ with defined hardware and software components, significantly reducing the engineering effort. Key components such as inspection systems, labelling devices or printers are bought in and integrated into the machines, as required.

In addition to its small and compact case packer systems, TR also builds large, bespoke packaging systems – some of them as much as 80m in length. A machine of this size has to be very modular in terms of its design, not simply from an installation standpoint, but also for transportation, which would require the use of several delivery vehicles.

As a consequence of this, TR has opted for decentralised design principles as far as the electrical installations are concerned, and these are addressed at the earliest planning stages for the machine. As TR’s hardware planning specialist, Hermann Schindler puts it: “We want to keep the installation lean, and don’t want to have to route cables 50 or 100 metres into the cabinet.” As part of this strategy, the company uses decentralised frequency converters located close the machine sections they control, rather than being housed in remote cabinets.

TR is currently working on a project for a Swiss pharmaceutical company. Here, pharmaceutical products are packed in small boxes that are subsequently conveyed on any one of ten production lines via supply routes, from where they are transported to a lower level via spiral conveyers and then routed to branch terminal lines.

Two robots place the packages on pallets that are carted away on linear carriages. The filled pallets are shrink-wrapped before undergoing a contour check and having an information label applied. At the end of the process, the finished pallets are transported to a high-bay warehouse. The system operates fully automatically, only requiring manual replenishment of shrink-wrap film once every four hours. 

A large number of sensors and actuators are integrated into this system in order that the products are correctly identified and routed in a timely manner towards the appropriate packaging station. This inevitably involves a great deal of cable routing and interconnections, and to minimise complexity TR uses Murrelektronik's Cube67 fieldbus system as the backbone of the system’s electrical installation.

Since the Cube67 fieldbus modules are easily connected together using prepared cable sets, TR's engineers were able to implement a flexible arrangement whereby modules could be quickly assembled or disassembled to meet future modification or expansion requirements. Cube67 is easy to work with and offers a convenient ‘plug-and-play’ approach. For example, an additional Cube67 module can be integrated into the system simply by connecting it to nearby module using a Murrelektronik hybrid (data and power) cable. These double-ended hybrid cables are also designed to reduce the risk of wiring errors.

Some15 Cube67 ProfiNet bus nodes are installed on the machine destined for the Swiss pharmaceutical customer. The modules collect information from sensors (mainly light curtains that detect the position of the product) and transfer appropriate command signals to the machine’s valves and actuators.

The fieldbus system oversees some 70 drives in this installation. These SEW motors, located at various positions along the conveyor line, are equipped with integrated frequency converters. This arrangement avoids the need for field switch boxes and terminal boxes, thus saving space. The drives are connected into the Cube67 system using Murrelektronik’s Movimot function module.

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

With Cube67, TR has been able to build a system that is both practical and versatile. Moreover, thanks to the modular nature of this fieldbus system, future expansions and modifications can be accomplished quickly and easily.