The networking of drives and controllers is an accepted practice these days. Numerous network protocols are routinely employed in industrial environments across the world. Among these, Ethernet TCP/IP, perhaps by virtue of its being more synonymous with office applications, is less familiar on the factory floor than might be expected, explains Mark Daniels of Rockwell Automation.
Unlike decidedly blue-collar protocols like DeviceNet, ControlNet and ProfiBus, Ethernet TCP/IP was not conceived primarily as an industrial protocol. But while its apparent lack of industrial street-credibility might make the ubiquitous Ethernet seem a little too much of a ‘one-size-fits-all’ solution for industrial control applications, EtherNet/IP – the industrial ‘flavour’ of Ethernet – offers enough advantages over the native industrial protocols to make it a serious candidate worthy of consideration in industrial applications.
Ethernet as a network has been around for a long time and over that time has evolved to become a very efficient way of making information widely and easily accessible across a variety of platforms. It is, after all, the technology that forms the bedrock of the internet. Its long history and broad usage has made it a cost-effective and reliable networking solution that is readily understood by non-specialist engineering support personnel. Ethernet’s ability to move information around networks and across network boundaries also makes it a powerful tool in the industrial environment.
It’s 2am: are your drives still running? If they’re networked using EtherNet/IP, you could know the answer in seconds, no matter where you are. Production line problems invariably happen when it’s most inconvenient. The strength of EtherNet/IP networking is that it can effectively deliver drive information and control when and where it is required. What it lacks in robustness compared to ControlNet or scalability compared to DeviceNet, EtherNet/IP more than makes up for in connectivity. But connecting drives is just the start: Because of Ethernet’s plug-and-play connectivity with the wider network infrastructure, drives connected over an Ethernet IP network are able to deliver diagnostic information via a standard web browser, just like any website. If a drive triggered an alarm or became faulty, text messages to pagers or mobile phones can be delivered via the same medium.
The ability for information – be it diagnostic data or commands – to flow effortlessly internally and externally across network boundaries is a great strength of Ethernet connectivity. But that’s not all. In purely practical terms, there is a significant labour and material cost saving from not having racks of I/O modules and wires running everywhere just to communicate with drives.
Drives wired using discrete or point-to-point wiring require multiple discrete and analogue I/O modules, along with the associated wires snaking through panels and panel interconnects. Users also have to take the time to buzz out wiring during installation, or again if there are problems with I/O operations later on. All of this results in increased labour time that can be avoided with EtherNet/IP networking.
With Ethernet, a single cable removes the need to run a multitude of wires through conduit and trunking. Dozens of drives can be networked over just one cable and, once the Ethernet connection is made, functionality testing is simply a matter of ‘pinging’ the required device from any Windows PC.
Using readily available software tools, EtherNet/IP allows facility managers to have a virtual ‘window’ into the drive, providing complete access to metering data, diagnostic values, configuration parameters and fault information. Viewing this information gives staff time to correct production issues before they can impact the rest of the process. In addition, if a drive faults, the maintenance staff will have a significant amount of information available to enable them to troubleshoot the problem.
In a situation where a drive or motor is beginning to operate outside of established parameters, users will know because the drive or controller software can be set to inform them directly. Drive configuration options are available that can e-mail or page someone with an alarm before a problem occurs, after a problem or faults occur and after an alarm or fault has been cleared. A hyperlink included in the e-mail message can be used to launch a web browser connected directly with the drive that sent out the message.
Additional software tools can be launched from the browser to allow complete access to the drive’s information. Not only is this a very useful facility for front-line support, but EtherNet/IP also delivers a very cost effective way for OEM’s to troubleshoot when offering support contracts. Cost savings from being able to troubleshoot online are significant because often an engineer does not need to be dispatched over long distances to repair or adjust a system.
Readily available wireless Ethernet technology makes life even easier by allowing maintenance personnel to roam freely to wherever a problem occurs. A wireless Ethernet card in a laptop or hand-held device and wireless access points on the factory floor are all that’s required to keep ‘connected’ to the network. The laptop becomes both the means of alerting that a problem has occurred and the tool to fix it. That makes it a very powerful tool indeed.
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