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Drilling with Ethernet
Specialty machine toolmakers embrace modern controls
Joseph Ogando, Senior Editor -- Design News, December 7, 2008
Walking around the recent IMTS show, the growing reliance on Ethernet-based controllers was plain to see among the new offerings from the world's biggest machine tool vendors. But makers of smaller specialty machine tools have been embracing Ethernet, too.
One case in point is Kays Engineering, a maker of gun drills. In past machines, Kays relied on PLCs to control its servo-driven drills. A simple gray scale display served as the operator interface.
And that kind of simple control system did the trick in the past. As Kays' Controls Engineer Brandon Snell explains, gun drills have relatively simple motion requirements. “You obviously have to control the feed rate of the drill and spindle speed,” he says. “Beyond that, we have to carefully control position in the drilling axis, usually to less than a thousandth of an inch.”
PLCs can handle that kind of control task without a hitch. Yet, Snell says there were opportunities to deliver on emerging customer preferences by moving to a new controls architecture. Gun drills, for example, have tended to be stand-alone pieces of equipment. “What we heard from our customers is that they wanted to incorporate our machines into their plant-wide automation networks,” Snell says. Customers also showed a preference for scaleable control systems, easier programming through structured-text and ready-to-go function blocks, and operator interfaces with Internet connectivity and rich media capabilities.
To meet these goals, Kays moved to a Windows-based, DIN-mounted, embedded-PC controls' package from Beckhoff Automation. Kays selected a Beckhoff CX9010 Ethernet controller with Intel IXP420 CPU and XScale technology for its Eldorado series drills, which are aimed at job shops. For its higher-performance DeHoff machines, Kays went with a CX1010 with a 500 MHz Pentium MMX-compatible processor. Both the CX9010 and CX1010 run TwinCAT NC PTP software, which provide integrated motion control functionality. Kays also upgraded its HMI displays, adding full-color, 6.5-inch Beckhoff CP7829 control panels.
Perhaps the biggest change brought about by the controller upgrade involves a greater reliance on Ethernet for machine connectivity and even real-time control. Snell says the Ethernet-friendly control architecture gives Kays' customers the ability to deliver custom content and Internet connectivity to the HMIs, as well as pass data to higher-level systems.
And then there's real-time control. With the change to Beckhoff's embedded PCs and the various servo drive models, Kays is now able to use EtherCAT as its motion bus. Snell says the switch to real-time Ethernet control has improved machine performance noticeably. “We haven't quantified the improvement yet, but the deterministic Ethernet is faster and more immune to noise. And that results in better position control in the drilling axis,” he says.
The Ethernet backbone also makes the machines easier to build and troubleshoot. “One thing that led us to EtherCAT was the almost 'plug-and-play' functionality it brings to our machine design,” Snell says. Previously, the servo drives and VFDs on the Eldorado and DeHoff machines required an analog 4-20 mA loop and six different types of cabling. “With EtherCAT, we've eliminated those complex cable runs and given our customers a more accurate machine,” Snell says.
