Machine Controls: It's All About Platform

Factory Automation Systems: Which hardware and software platforms do you use for your machine controls? The results of Control Design's recent Reader Survey make it clear that you choose machine control that fits you best.

By Rich Merritt

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Feb. 2005, Cover image We get, and sometimed give a lot of mixed messages about control platforms. We regularly hear from market research companies that tell us PLCs will be replaced by PCs and hybrid controllers. We also hear from control equipment vendors who claim they dominate the machine control business with their particular control platform. We also continually publish articles and application stories that describe new technology and print "opinions" that predict controller specifying trends and upcoming technology developments—some of which boggle the mind.

We think we have a firm grasp of what’s going on, but once in a while we like to check with you, the big and influential group that you are, and find out what control platforms you actually do use.

To get a clear, unvarnished picture of what you and your machine-building colleagues are doing, we simply asked: “What control platforms are in your machines today?”
The answer provided by our survey respondents were very clear: You like PLCs and PCs.

Survey Says . . .
The survey results clearly show that you overwhelmingly prefer PLCs and PCs to hybrid controls, custom controllers, and "other solutions," which include CNCs, FPGAs and relays. Over the past few years, you have slowed the development of your own custom control systems. It’s likely that the 20% of you who report using custom control systems are simply getting the last few miles out of old systems developed years ago.

The numbers add up to more than 100%, because many machine builders use both PLCs and PCs, depending on the machine or application. "We've always used PLCs and PCs," says David Schoenly, control engineer at VAI. "The PLC is used to control the equipment and the PC is used as an HMI."

VAI builds metal processing machines. "The machines are large, about 1,000 feet in length," says Schoenly. "They are used to process metal in strip form. The processes include uncoiling, welding, shearing, cleaning, annealing, application of zinc coating, rolling, application of dry lube, side trimming and recoiling. These processes can be combined or supplied on an individual basis."

Nick Merriwether, a control engineer at Integrity Machinery, also specifys both PLCs and PCs for his comany’s packaging and food processing machines. "We use a variety of PLCs and some PCs," he says. "Most of the packaging is PLC. Some of the processing is PC-based, mostly the high-speed color sorters."

Some respondents just use PLCs, some just use PCs, and some use both, but almost nobody uses hybrid controllers, which are supposed to be a blend of PLC and PC capabilities. Some market researchers call these "programmable automation controllers" (PACs) and some vendors call them hybrids, but you don't seem to call them anything at all. Only 8% of our respondents claim to use them as a control platform. Some of you tried hybrids, and went back to PLCs.

Decisions, Decisions
It appears that machine builders don't make decisions about their control systems lightly. But when they do, they stick to it. A whopping two-thirds of respondents have been using the same control platform for more than five years. Only 5% made a change in the past year.
System integrators and custom machine builders are part of that 5%, because they build all kinds of machines, can tailor a control system to a particular application, and can use the latest and greatest equipment. "New technologies allow better control in a smaller package," says Greg Kempfer, controls engineer at M.C. Dean CIM Associates. Kempfer has built just about every kind of machine control system there is, starting with relays.

"I work for a rather large integrator, which has exposed me to a greater variety of machinery as we meet the control demands of our clients. It also allows flexibility as demands change. For example, modern controllers let us make changes to a machine to enhance its capabilities with minimal changes to the hardware."

A machine builder who has a product line of robots, material handing equipment, sheet-metal processing machines, packaging equipment or machine tools, has to be more selective.

This kind of machine builder must amortize its investment in a particular control system over several years. The builder must choose a control system that is flexible enough to support several different products, be able to upgrade the controls when necessary, and support the control system in the field. Small wonder that machine builders try to standardize on a single platform.

Packaging machine OEM Rovema traditionally supported three different control systems, each from a different supplier. According to Travis Holley, director of engineering at Rovema, this posed a real challenge. "With multiple control systems, we were sometimes unable to make changes in a timely manner and could not provide full support for our machines with internal resources," he explains. "When a customer requested maintenance or upgrades, we often had to wait for the supplier to respond."

When Rovema wanted to expand its product line, it realized it needed to standardize on one control platform across all its products. In 2000, it launched a new packaging product based on a hybrid controller; in 2002 it standardized on the hybrid controller; and it has since put the controller on eight product lines. "If we continued to try to support multiple control systems, there's no way we could have expanded our product line with the same staff," Holley says.

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