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Unmanaged switches simplify networking of robot cells

23 May, 2022
HandlingTech finds that 16-port switches offer advantages when handling large amounts of data

The German automation specialist HandlingTech develops and implements modular handling systems for industrial manufacturing sites. In its robot cells, it uses unmanaged 8-port and 16-port switches to simplify the networking of Ethernet nodes.

Managing director Jörg Hutzel founded HandlingTech in 1994 in his parents’ basement. Today, the company is well-known for its robot automation expertise and specialises in creating customer-specific systems based on standard robot cells. Its automation systems enable full automation of industrial processes as either stand-alone machines or as machine adaptations. The modular systems can be adapted easily and economically to customers' machine-specific requirements.

Since the start of 2019, HandlingTech has been using unmanaged 8-port and 16-port switches simplify the networking of Ethernet nodes in standard robot cells. The “door openers” were 8-port switches which use push-in terminals for the power connection simplify the wiring of the individual switches. The Murrelektronik Xelity devices prioritise Profinet protocols and thus give preference to Profinet data over Ethernet data. They can transfer data packets at speeds of up to 100 Mbit/s.

HandlingTech connects the switches to its industrial PCs, robots, and safety and remote maintenance systems via an Ethernet TCP/IP interface on the outside of the control cabinet so that it does not have to be opened for service work. This means that most of the ports are occupied, leaving one or two ports as a reserve for measuring tasks in the cell. 

Eight-port switches can reach their limits when large amounts of data are involved. In such cases, HandlingTech is using Murrelektronik Tree16 TX 16-port unmanaged switches with two Gigabit Ethernet uplink ports and 14 Fast Ethernet downlink ports. Unlike some other switches on the market, these do not consist of two interconnected 8-port switches which are not designed to handle large amounts of data. “Our device is a pure 16-port switch with a matching controller chip,” explains Dennis Zimmer, Murrelektronik’s product manager for switches. “The composite switches may be less expensive, but our 16-port switch is reliable and has the necessary power." 

In applications where several large robot and processing modules are networked together, Gigabit ports on 16-port switches can be essential. For example, in some large systems for machining shafts, machine tools are positioned between two HandlingTech  robot cells. The first cell removes the workpieces from a grid box and loads the machine tool. The workpieces are fed to the system via a grid box in which the shafts are placed randomly.

The robot uses path planning based on a point cloud to grip the components. A point cloud is generated based on data from a vision system above the grid box to calculate the best approach point for the robot gripper. The robot, equipped with an interchangeable gripper system, picks up the component with a magnetic gripper and deposits it on a clipboard, where it is aligned. It then loads the tool to machine the part. The robot in the subsequent cell unloads the machined shafts from the tool and packs the parts directly into cartons with a blister layer. 

The camera data is processed autonomously on a separate computer. In this system, the 16-port switches are responsible for the communication between the robot systems. The two Gigabit ports ensure communication with a higher-level controller, while the remaining 100 Mbit ports collect data from the various participants in the cell.

Henning Schultz, an electrician and electrical designer in HandlingTech’s production department, says that the small size of the unmanaged switches “allows them to fit easily next to a power supply, contactor or relay without having to create extra space on the DIN-rail or in the cable ducts. I also find the push-in terminals very practical as many competitors still have an additional plug with screw caps, which complicates the connection.”

Not only are new plants are equipped with the switches, but older ones are as well during retrofits. Many older plants rely on Ethernet and are not yet equipped with a bus system. HandlingTech’s electrical engineers have installed many unmanaged switches during retrofits at customers’ requests. In retrofits, space is often the limiting factor, and compact switches are a big advantage.

Each HandlingTech robot cell now uses two switches to separate Ethernet and Profinet where possible. “Even if only four or five ports are occupied, in the highest expansion stage, we need all of them,” explains Schultz. “It is also important for us, as well as for the control cabinet-builders, to have a certain design standard. Murrelektronik switches are now part of almost every installation of ours.”


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