Making robot cells safe

A plant manufacturer automates small and medium-sized robot cells for its SME-level customers. The perfect coordination, monitoring, and visualization increases production quality, efficiency – and safety.

A mat pullout pushes the finished wire-frame mat from the welding machine and right under the industrial robot’s special gripper. This gripper holds and lifts the wire frame, rotates it 180°, and transfers it to a second gripper, which then sets it down with millimeter-level accuracy.


The next wire frame is placed on the stack by the industrial robot, without being turned over beforehand. The next frame is turned again. “Thanks to this action, the longitudinal wires on the wire frame are always on one level, reducing the stacking height,” says Andreas Pfeifer, Head of Project Engineering at Krüger Industrieautomation GmbH. “That means more wire frames will fit on the truck, and that reduces transport costs.”

New mission for robots

Krüger specializes in plant engineering and robotics for small and medium-sized enterprises. The machine builder also upgrades its robots so they can be reused in new or existing plants. Just like this robotic cell with a lifting portal and gripper solutions for a metal construction company.

Controller for communication and safety

Like in other systems with one or two robots, Krüger uses a fail-safe Simatic S7-1200F  programmable logic controller as standard. “It enables us to control and monitor all components in the robot cell independent of the robot program,” Pfeifer says. “In addition, all communication between the robot and the welding machine goes through the controller and the open industrial Ethernet standard Profinet.”

As well as standard communication, this also applies to safety-related communication. “The robot is also linked to the welding machine with safety functions like an emergency stop system and shared protection areas,” explains Pfeifer. Because the robot has the Safe Operation option, there are safety areas for both operators and robots.

All information on the safety functions, including emergency stop, safety doors, and end-position sensors, is available right in the controller and is visualized on a panel. “This allows the customer to quickly diagnose faults all the way down to channel faults,” Pfeifer says.

More efficient engineering

There are major benefits in engineering, too: With just a single software program and programming language, programmers can develop standard modules for plants of different sizes. Because the safety function is integrated in the Simatic S7-1200F, complex wiring for safety communication is no longer necessary. And input and output modules on each gripper also collect the signals from the sensors in order to communicate them through a single Profinet cable. “Because there’s now very little cabling between the controller and the robot, engineering time is reduced by about 50 percent,” says Pfeifer.

Diagnostics via Web server

Krüger Industrieautomation would like to offer its customers a new service in the near future: The Web server integrated in the controller will be used 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,” Pfeifer says enthusiastically.

Because there’s now very little cabling between the Simatic S7-1200 and the robot, engineering time is reduced by about 50 percent.
Lars Krüger, CEO of Krüger Industrieautomation GmbH 

March 2019

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