Proportionally complex PLC, PC-based controls (Packaging + Processing OEM)

OEMs seek to match the their chosen controls platforms to the complexity of the problem being solved.

In the beginning, there were chips. Well, no, actually there were relays. But after Jack Kilby invented the integrated circuit, in 1958, everything began to change. For machine control and countless other fields, this marked the start of a logarithmic acceleration in the evolution of capabilities, productivity, and complexity.

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Another large step forward came a decade later, when Richard E. Morley invented the modular digital controller, or Modicon, which soon went into production as the world’s first PLC. Suddenly, relays were no longer discrete wear parts, labor-intensive both to install and to replace, but miniscule semiconductors clustered on tiny chips that would, with the passage of several decades, become both ubiquitous and incredibly inexpensive.

Although it’s difficult to say whether the controls industry is still on a logarithmic climb, control systems certainly do continue to evolve. Thanks to controls manufacturers’ ongoing improvements and new offerings, OEMs today are finding they can upgrade the industrial control systems going into their equipment in many of the same ways consumers upgrade their home computers. Plus, OEMs are looking for many of the same things that any other consumers are looking for, including speed, precision, reliability, flexibility, economy, and ease of use.

PLC/PC divide narrows
The distinction between PLC- and PC-based systems has blurred considerably in recent years. Unlike the early days, when specialized microprocessor chips made a huge difference in distinguishing among different PLC manufacturers’ products, today the move is toward using off-the-shelf chips.

“Semiconductor technology has gotten so advanced that for very few dollars you can take an off-the-shelf Intel processor and it will just run circles around the old-school chips,” says Chris Thomas, senior software engineer with Raleigh, N.C.’s Axon, powered by Pro Mach. The company makes shrink sleeve applicators, stretch sleeve applicators, and heat shrink tunnels among other systems.

Thomas says that for packaging control systems, speed is critically important. “I just want sub-millisecond cycle time,” he says. The fact that PLC makers are now using some of these off-the-shelf chips is a smart move, Thomas noted, simply because it will allow them to modernize—and run—more quickly. “What has enabled the fast machines is the off-the-shelf PC hardware, not necessarily the operating system,” he says. “But I don’t care about Windows. We could also use Linux, VxWorks, embedded hardware, and so on. I think it is important to use what makes the most sense for your application.”

In the area of HMIs, however, Windows can be a useful tool, something even Thomas acknowledged. “I’m much more a fan of the HMI being the Windows box; then the PLC can just rock in the background,” he says.

In search of flexibility 
“For us, the flexibility to easily integrate and communicate with third-party devices and controllers is key,” says Michael McCallum, a controls engineer with Toronto-based Plexpack, which designs and manufactures flexible packaging solutions including bag sealing and shrink packaging. “We’re constantly integrating devices such as camera and printing systems that have been selected by the end user and B&R has allowed us to do this with ease.”

Plexpack recently switched over many of its control systems to B&R C70 controllers, which McCallum says at their core are highly integrated industrial PCs. “However, B&R has done an excellent job making their engineering software very user friendly, which has minimized the learning curve when transitioning from a more traditional PLC and HMI solution,” he says.

The company’s Automation Studio provides the engineering tools required to create machine logic and graphical interfaces in one compact package. And it is indeed flexible.

“With a PLC-based system, you are limited to the hardware configuration of the controller that was initially specified for the project. While it is possible to add expansion modules to some traditional style PLCs, if any of them stop working or are missing, the whole system will fault out,” McCallum says. “With B&R’s platform, we’ve created one standard software program that we use across an entire model line of machinery, regardless of the options/accessories attached to the machine. This is possible because the B&R system will recognize the installed hardware and the software will automatically configure and run the devices on the machine.” McCallum says it recognizes a new device by the station number assigned to the hardware that has just been connected, which is preset in the software, and if it is not present the system will continue to run without the optional hardware. Despite the initial investment involved in developing that part of the software, McCallum says that plug-and-play-like feature has been beneficial to Plexpack and its customers, allowing machine options to be installed in the field by the end user.

The company is using the same B&R C70 controller on a variety of its newer machines, both large and small. “I think that trend is going to continue because of the flexibility it provides and the additional value-added features we can integrate into the equipment,” McCallum says, and the upfront cost has become a non-issue. “Some of our older equipment still uses PLCs, without interfaces, that cost roughly the same as this integrated touch screen controller.”

McCallum has been pleased with the switch. “Previously we typically used ladder logic for all of our applications,” he says. “With B&R we have found it very beneficial to use a variety of the languages specified in IEC 61131-3, depending on the application. We now predominately use structured text for most of our basic applications and have started to use C, as it is fully supported in Automation Studio, for some of our more complex tasks. But its flexibility is what really sold us on the C70. The ability to control our simplest machine all the way up to our most complex machine multi-axis integrated solution was the real deciding factor for us.”

Nailing it, every time
Mike Krummey is another convert to PC-based controls, depending on the application. Krummey heads electrical engineering for Matrix Packaging Machinery, Saukville, Wis., also powered by Pro Mach. Matrix has for years produced intermittent v/f/f/s machines. When the company decided several years ago to develop a machine that would operate continuously, it fell to Krummey and his staff to find the technology to make
it happen.

“I believe in using the appropriate level of technology when possible,” Krummey says. “Simply put, that means if it’s a simple application, use simple logic controllers like a PLC or even a relay replacement.” More complicated systems, however, may be better suited to a PC-based control system. “In the case of our continuous motion machine, because of the complexities required by the correct way to do it, a PC-based system was the only option that we had.”

Although speed of execution was a consideration, Krummey’s larger concern was precision. In researching how to build the appropriate control system, Krummey says, “we very quickly came to the conclusion that the correct way to do this was with an extremely fast motion network. To do something like we were planning, I need to know when I’m moving something down to the microsecond. If you really want to do things right, you need to know where things are at.”

Matrix decided to use the EtherCAT network as implemented by Beckhoff, and rolled out its continuous motion machine. Even though its adoption of Beckhoff controllers for this product line has been successful, Krummey says it doesn’t indicate a wholesale migration, maintaining his commitment to using appropriate levels of technology on each of the company’s machines. And doing that is inextricably tied to the skill level of the people who will be working on keeping the machinery running day in and day out.

“What you want to do is make it as easy for them as possible to keep your machine in automatic mode cranking out the bags, because that is how a machine makes money for people,” Krummey says. “That’s what they remember when they go to purchase another one. It’s all about bags per hour and hours in a year that the machine is up, producing.”

Using control systems that are as simple as possible helps in that regard. “Obviously, the more complexity you have, although it may be needed, the more chance you have for operational peculiarities. But you also have more chance of damage from cleaning the machine or from doing routine maintenance on it, and this is true for both electrical and mechanical. The more complex, the more chance for something to go very wrong.”

So where is the controls world headed? Clearly, toward faster and more powerful hardware, thanks to the progress of technology in general. But exactly what trajectory? Well, that all depends who’s got their hand on the controls.

Newsletter Date

Thursday, February 16, 2017
https://www.pp-oem.com/products/machine-control/proportionally-complex-plc-pc-based-controls?spMailingID=16621216&spUserID=MjMxNzg4MjI0MzA0S0&spJobID=961799689&spReportId=OTYxNzk5Njg5S0


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