Editor's Choice


IP67 PLCs control autonomous conveyor modules

January 2023 Editor's Choice Motion Control & Drives PLCs, DCSs & Controllers

Krups Automation, a company with its main plant in Dernbach Rhineland-Palatinate, Germany, is a market leader in assembly and test automation. The company specialises in automation systems for the efficient linking of assembly and testing stations. With its LOGO!MAT eCart, Krups offers a highly available conveyor system that breaks new ground – with actively powered, intelligent workpiece carriers that can rotate, lift, clamp or tilt workpieces.

Philipp Krups, second-generation head of the company, explains the basic idea behind it: “In a conventional roller conveyor system, the drive is located in the conveyor track. This involves a lot of mechanical parts in the track, and also the associated amount of wear. With permanently installed systems, maintenance is therefore always a problem. That’s why we wanted to turn the system round and remove the maintenance from the track.

“We therefore developed a passive track that is completely maintenance free. The whole technology and electrical system is now located in the carts, the so-called eCarts. These electrically driven carts have a self-diagnostic function and can be discharged from operation, if required, for preventive maintenance. This means that downtimes are reduced and the track remains operational. It also makes any later expansions to the conveyor line very easy to implement. The eCart system furthermore makes it possible to implement more flexible production processes with smaller batch sizes. It could even be said that it is an Industry 4.0 conveyor.”

The system consists of a few standard modules: rotate modules, shuttle modules, stopper modules and indexers. These units are combined in a layout according to individual customer requirements and connected to the onsite control system of the plant. The conveyor system supplies the customer’s production system with report data and enables the implementation of bidirectional communication interfaces. Several large German automobile manufacturers are now using the systems in their battery production for electric vehicles.

Decentralised control for modular conveyor systems

“Previously there was always a main controller, to which all signals were routed. This partly involved point-to-point wiring, but increasingly often also decentralised I/O units. The problem here was the programming in one sequencer. However, if any condition at switch-on or after an emergency startup is present that is not represented in this sequencer, the users must move units by hand in order to restore a known situation,” explains Christian Mies, control developer at Krups. “A conveyor system has to be programmed differently in order to eliminate the need for manual interventions. Conditions and appropriate reactions have to be defined that are suitable for all situations.” Ideally, every module should be autonomously controlled.

Each module essentially operates as a ‘black box’ which simply communicates bidirectionally with the central controller via a bus connection. The module runs its program in order to perform its particular task: rotating, transferring, traffic monitoring and reporting of module status. Each module is therefore controlled – exactly according to the development – and perfectly implements all possible sequences. A plant controller is installed at the level above this and controls the overall flow. However, the actual positioning sequences and the monitoring of conditions is taken over by each controller at the module.

In this way, Krups no longer has to intervene in the control of the overall plant, nor does the plant operator have to control the conveyor system modules. Only the communication between the general controller and the modules has to be implemented at a base level. In-house, Krups calls these conveyor system modules which have their own intelligence ‘smart modules’. The company therefore looked for autonomous controllers ten years ago, which could be installed directly on the modules.

Self-built IP67 controller

“At that time we already looked for compact controllers with IP67 protection. However, there was nothing on the market,” Mies says. Krups therefore first helped itself: “We had our own controller built on a board, fitted all M12 plug connectors, and placed everything in a housing. This housing had to be provided with drill holes plus a pneumatic system and a display. These were very big units and relatively difficult to manufacture. We had to have the boards built, the housings assembled, and everything wired up. Although this was successful, it was a laborious task,” says Peter Krups.

Since Turck launched its TBEN-L-PLC block controller on the market a few years ago, Krups has been able to save the effort required for a self-build. The company is now using the IP67 controller in many machine models, not only in the eCart system. The control system for every conveyor system element was written in Codesys. The communication to the drives or valve blocks and other components of the module is implemented via a bus interface, with communication to the main controller mostly implemented via Profinet.

“We now have the benefit that the modules can be deployed immediately and without the need for any other field programming device. In the ideal situation, the customer just has to connect the 7/8-inch plug connector for 24 V and the Ethernet connector for the bus connection,” Mies adds.

For an international company like Krups, the sheer range of protocols offered by the compact controller means it pays for itself, he says: “We can serve the US market with Ethernet/IP in exactly the same way as the European and Asian market, where the protocols are mixed. We are currently concentrating on Ethernet/IP and Profinet, but Modbus TCP would also be possible in principle if this is required by a customer. The great thing here is also the fact that all the Codesys licences are contained in the Turck device. The licence is there and we can use it regardless of the fieldbus the customer uses. We can even use them when we sometimes need a small main controller, because the master licences are also available.”

eCart system saves power in battery production

The specifications of the eCart conveyor system in battery production already make it clear that the manufacturer is serious about e-mobility. With 130 self-driven carts on approximately one kilometre of conveyor track, the stage of small-series production has long been left behind. Krups usually installs around 70 turntables and about 140 stoppers on the track. Ten stoppers, and each of the rotary modules, use a TBEN-L PLC as a gateway to the customer’s main controller. This considerably reduces the number of bus nodes required for the customer.

To change direction, the carts are moved by transfer units to parallel tracks, or their direction is changed by turntables. Unlike most conventional systems, it is possible to communicate with the carts of the eCart system. NFC (near-field communication) units are provided at the stoppers in order to use the TBEN-L-PLC as a gateway to implement communication between the main controller and the carts. In this way, carts can be removed, depending on their state or the presence of warning messages. Another benefit: when the carts are waiting, they do not consume any power – unlike conventional roller conveyor systems in which the drives normally continue running – even if no boxes have to be moved.

The sensors and actuators of the modules are connected directly to the TBEN-L-PLC. The block controller provides eight universal channels on four sockets, which can be set automatically to the required configuration as inputs or outputs. If other I/Os are required, Krups can expand the number of signals required with the BL compact I/O module via a CAN bus connection. The BL compact modules are likewise designed with IP67 protection, and are mounted directly at the units.

IP67 protection saves wiring

It is not only Krups that appreciates the labour savings that lie in Turck’s IP67 technology, but customers are also convinced by the solution. “Just routing the 24 V cables and signals to the twelve controllers on the stoppers and labelling would be very labour intensive. The price of the TBEN-L-PLC covers this easily,” Mies says.

The eCart system is not only energy-saving and fail-safe, it also enables more flexible processes as per Industry 4.0 scenarios. Through communication with the workpiece carriers, greater product variance can be achieved.

For more information contact Turck Banner, +27 11 453 2468, [email protected], www.turckbanner.co.za



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