Robotics for small and medium-sized enterprises

Plant engineering specialist Krüger Industrieautomation GmbH relies on SIMATIC S7-1200F for the automation of small and mid-sized robot cells in order to increase production quality, efficiency – and operator safety.
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Robot cells tailored to customer requirements

Founded in 1999 and based in Wipperfürth, Germany, Krüger Industrieautomation GmbH specializes in plant engineering and robotics for small and medium-sized enterprises. The company’s second major division is closely related to this: Krüger upgrades its robots so they can be reused in new or existing plants. One of the new plants developed and built in close cooperation with its customers includes a robotic cell with a lifting portal and gripper solutions for a metal construction company.

A mat pullout pushes the finished wire frame mat from the welding machine directly under the special gripper of the industrial robot. This gripper holds and lifts the wire frame, rotates it 180°, transfers it to a second gripper attached to a lifting portal, and then returns to the removal position. Meanwhile, the lifting portal lowers and places the gripper with the wire frame to a calculated position above the stack.

The next wire frame is placed on the stack by the industrial robot itself, without being turned over beforehand, so stacking is always in alternating fashion. “Thanks to this procedure, the longitudinal wires of the wire frame are always on one level, reducing the stacking height,” says Andreas Pfeifer, Head of Project Engineering at Krüger. “For large quantities, more wire frames will fit on the truck, reducing transport costs for the customer.”


Controller for communication and safety

As with other systems with one or two robots, Krüger uses a SIMATIC S7-1200F Basic Controller as standard. The advantages of this fail-safe programmable logic controller (PLC) won over Andreas Pfeifer, Head of Project Engineering at Krüger.

“It enables us to control and monitor all components in the robot cell independently of the robot program. In this case, it’s the end position sensors for monitoring the gripper position,” Pfeifer says. “In addition, all communication between the robot and the welding machine goes through the SIMATIC S7-1200F and via Profinet.”

In addition to standard communication, this also applies to safety-related communication. “The robot is also linked to the welding machine in terms of safety, with an emergency stop system and shared protection areas,” explains Pfeifer. “They are interconnected using Profisafe.” Since the robot has the Safe Operation option – that is, its actions can be limited to certain areas – the operator can also use the controller to block or enable specific traverse paths depending on signaled states of the welding machine. “This makes very flexible safety areas for operators and robots possible,” Pfeifer emphasizes.

All information on the safety functions, including emergency stop and safety doors as well as end position sensors, are directly available in the controller and are visualized on a SIMATIC 
KTP700 Basic Panel. Pfeifer says: “This allows the customer to quickly diagnose faults all the way down to the channel fault.” The operator also selects the recipes on the panel, depending on the type of wire frame or stack, which are then communicated to the robot via the controller just like the signals from the welding machine or gripper sensors.


Consistency across the board

Shorter commissioning times, simple operation, and last but not least, low costs – SIMATIC S7-1200 impresses Krüger with its numerous advantages.
Because there is now very little cabling between SIMATIC S7-1200 and the robot, engineering time is reduced by about 50 percent.
Lars Krüger, CEO of Krüger Industrieautomation GmbH

In previous years, Krüger used a SIMATIC S7-300 CPU as standard in its robot cells, combined with safety relays or special safety controllers. “Since switching to TIA portal, we have been using SIMATIC S7-1200F for smaller plants and SIMATIC S7-1500F for larger plants,” explains Pfeifer. “This is the optimal solution for us: a CPU with Profinet interface for communication with the machines, including safety functionality – and all this at a lower price than in the past.”


The programmer only has to know one software and programming language and is able to develop standard modules for both controller families. Information about the safety devices can now be easily visualized, and complex wiring for safety communication is no longer necessary. “This shortens commissioning time,” Pfeifer emphasizes. “SIMATIC ET 200SP input and output modules on each gripper also reduce the amount of wiring we have to do. They collect the signals from the end position sensors on site in order to communicate them further through a single Profinet cable.”

The future: diagnostics via web server

“Support with circuit diagram macros, manuals, and sample projects is exemplary at Siemens,” adds Pfeifer. In the future, he also wants to make use of the web server integrated in SIMATIC S7-1200 and develop pages for standardized diagnostics. “This will enable us or the customer to do initial diagnostics from home or on the road using a computer or mobile phone.”

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