Good migrations

Machine control upgrading can be a tough journey. But the trail can lead to improved ROI for you and your customers

By Rich Merritt

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May 2004 cover imageWhen a machine control system reaches early maturity -- say, in its second or third year of life -- you and your company might have a reason to smile. Bugs are gone, repair parts are readily available, development costs have been recovered, and the system runs reliably. You install it in every machine going out the door. With just a configuration tweak or an adjustment, it works well on every machine you make. The longer it works like that, the better its return on assets and return on investment. If it could just run forever, your accountant would be ecstatic.

Let's get real. Nothing runs forever. Even the three most-reliable devices on the planet--PLCs, DEC PDP-11 computers and a 1972 Datsun 510--fail eventually. Someday, support from the factory will stop, and parts will be found only on eBay. You won't be able to assemble your controls or repair the ones you have in the field.

Even if your system is running like a clock and parts are available, your dream of running forever can be shattered before its time by pesky customers who want you to add a few things to the system to bring it up to date. New customers may want to buy a machine that has a web browser or Ethernet communications, so they can connect to enterprise-level software. Existing customers may want you to update their machines for the same reasons.

Sometimes you can choose to upgrade key elements of the control system and begin the migration to new technologies slowly. Sometimes, however, you and your flock of customers have no choice but to leave everything behind and fly straight to a completely new control solution. Regardless, you'll need to know your options.

Risks and Rewards
Glasstech Inc. (www.glasstech.com), Perrysburg, Ohio, makes glass-bending and tempering equipment for the automotive and architectural markets. Steve Connell, manager of systems engineering, says hardware obsolescence and lack of support are risks, and clearly are reasons to upgrade.

"As spare parts become more difficult to purchase, prices can skyrocket and the resulting downtime while waiting for components increases," he explains. "In addition, those older DC motors require more maintenance."

The lack of diagnostics in old control systems and the availability of advanced diagnostics with new systems are additional reasons he lists for upgrading controls. "The lower level of diagnostics available in old systems makes it nearly impossible to predict the next failure," laments Connell. "With improved diagnostics, our machines can be more efficient."

Glasstech had been using a Mikul bus and 6809 embedded control system, which they had developed themselves some years before. Connell says the rewards resident in Glasstech's now-standard Rockwell Automation ControlLogix platform with integrated motion control are better machine performance and improved diagnostics, plus the controls are easier to operate. "On nearly all our glass machines, higher production rates are the result of the new controls," he adds. "It was a very big decision to go from an internally developed system, where all spare parts and repairs came from Glasstech, to off-the-shelf spares."

It often boils down to a short list of reasons why we upgrade. "There typically are two reasons our customers have for upgrading legacy control systems," says Ed Diehl, owner and principal engineer of Concept Systems (www.conceptsystemsinc.com), a system integrator in Albany, Ore. "First, the legacy system has become a maintenance issue or a potential maintenance issue because customers can't purchase replacement parts or support the software anymore." His second reason is that customers can improve their bottom line via productivity, quality or both with a modern control system. "Usually, the first item is why they look to upgrade, and then the clincher, in many cases, is when they can see other bottom line benefits to the upgrade," adds Diehl.

Doesn't Have to Be Hard
One of the easiest upgrades is to add a modern HMI/SCADA system to an existing machine control system. This might be suitable if the controls are working well and all you really need are some modern communications and Windows-based functions.

Virtually every HMI/SCADA software package on the market today has one or more interfaces to legacy PLCs, machine controls and CNCs. If you can find a package that fits your specific control hardware, then you can plug your legacy controller into the 21st Century. For less than $1,000 (much less when you get an OEM agreement), this will get you a web server, Ethernet connections, advanced HMI capabilities, data logging and data acquisition and all the advantages of a modern Windows architecture, including OPC, .Net, and database connectivity. You will be able to phone in from your home office to the customer site and perform remote diagnostics.

If you can't find a plug-in package that works out of the box, maybe a little hardware will help. Joel Young, vice president of engineering at Digi International (www.digi.com), says adding connectivity to legacy systems is a big part of Digi's business. "We make it possible to extend the life of existing systems with only an incremental investment," claims Young. "We provide a path by which connectivity can still be used as other components get replaced."

Young offers a processing environment example that has relevance in many discrete industry applications. "Chevron needed to integrate 200 of its Square D SyNet PLCs with Wonderware software via Ethernet," he says. "The existing PLCs used a proprietary system that required a specialized PC board. To further complicate the issue, the PLCs were no longer in production and were not Ethernet compatible."

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