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 real-time control over
Ethernet too.
One case in point is Kays Engineering. The company makes gun drills that perform deep-hole
drilling for a wide range of automotive, aerospace, medical and tooling applications.
In past machines, Kays relied on PLCs to control its servo-driven drills. A simple
grey 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 says,
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."
While PLCs worked fine, 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 had also
shown 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 an
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" Beckhoff CP7829 control panels. Snell notes that the
CP7829 is an IP65 rated display, yet it doesn't require a space-wasting
enclosure.
Kays has already made good use of the
embedded PC's programming flexibility and the new HMI to create some brand new
functionality for its customers. For instance, it added a new "drilling
parameters calculator" that generates feeds and speeds based on simple user
inputs related to material type and desired hole diameter.
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 notes that the
Ethernet-friendly control architecture gives Kays customers the ability to
deliver custom content and Internet connectivity to the HMIs as well as to 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."
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