Don't Over-Specify Ethernet Switches

Feb. 9, 2012
Industrial Ethernet Can Operate in Harsh Environments. But for Light Manufacturing and Assembly Operations, Industrially Hardened Ethernet Switches Can Be Overkill.
About the Author
By Scott Wohnrade, Scott Wohnrade is a network engineer at Yaskawa America's Drives & Motion Division ( facility in Oak Creek, Wis.When you think about selecting an Ethernet switch for a production line application, your first thought might not be of a switch primarily designed for office use. But using such a switch can be much more cost-effective than purchasing an industrial-hardened component.

Industrial Ethernet switches typically can operate in very harsh environments and withstand high temperatures, high levels of electrical noise, and/or large amounts of airborne dust and dirt. These industrial switches also feature very high mean time between failure (MTBF) rates, and often can be configured easily to operate in redundant modes—making them ideal for heavy manufacturing applications that can't abide any downtime.

But for light manufacturing and assembly operations, industrially hardened Ethernet switches can be overkill, with added features that are not worth the high upfront costs. This is particularly true in operations where some downtime can be tolerated. If assembly of a component is interrupted for a few minutes, the costs and consequences are generally minimal.

If your requirements tend more toward a long list of useful features at a competitive price, and if your manufacturing operations are relatively "clean," then an office-grade Ethernet switch can be the best option. We found this to be the case when we recently selected an Ethernet switch for our light manufacturing and assembly line.

Typical switch requirements include the right number and type of Ethernet ports. The switch should also be well constructed, provide electrical isolation, show status at a glance, provide management features, and have built-in troubleshooting tools.

[pullquote]At the Drives and Motion Division of Yaskawa America, we assemble products to order for our customers. For this particular application at our facility in Oak Creek, Wis., we assemble and test high-horsepower ac drives.

Each unit is assembled and tested based on Product Build Orders received from the Yaskawa business system. The build information is recorded as the operator moves to the next step in the process. Every unit gets an RFID tag as it moves from production to the test station. This movement of information is controlled by the Ethernet network, in which the Ethernet switches play a key role.

We use the Cisco Model SG300-20 for our application. Our selected switch has the right number of ports, specifically 18 10/100/1000 Ethernet ports, and two Gigabit Ethernet combo ports that can be connected to fiberoptic or copper cable. The fiberoptic connection option is particularly important for us as our environment includes a high level of electrical noise because we test motors and drives.

We can view switch status at a glance and easily determine power on, ports connected, speed and activity. Although our manufacturing floor environment isn't a high dust or dirt environment, we still required a fanless switch, a requirement met by convection cooling.

The ability to see port data transmission statistics is very helpful when looking for Ethernet network errors. Errors can be caused by speed/duplex mismatch, bad network cabling or misbehaving network cards.

Our selected switch also gives us the ability to add port descriptions, very useful for line device location and troubleshooting tasks. A further troubleshooting aid is a Port Copper Test feature.

The Link Aggregation Control Protocol lets us combine multiple switch ports to increase bandwidth. Alternately, this feature provides link redundancy between two devices, so one port can fail and the other in the group can stay connected.

Web-based and command-line interfaces are available for those who prefer text configuration, and port and VLAN mirroring is very useful in troubleshooting network and application problems. Switch traffic on a port can be mirrored to another port for analysis via a network analyzer.

Although the reliability of this office-grade switch might not equal industrially hardened switches in certain environments, we found that uptime was sufficient for our operations, and Cisco includes a limited lifetime hardware warranty in case of switch failure. The combination of features, low cost and acceptable reliability made these switches the right choice for our light manufacturing and assembly operation—and maybe for yours.