The general health of the programmable logic controller (PLC) market is a thing to behold.
According to Frost & Sullivan, the global PLC market has witnessed positive growth across all regions. The market, which experienced a strong decline in the early part of the decade, has bounced back strongly and is expected to reach $14.58 billion in 2018, up more than 40% from five years earlier. This growth includes the mature markets of North America and Europe, where uncertainty about economic standing had precipitated the earlier decline. Of particular interest is the Frost & Sullivan note that “the small and medium PLC segments will be instrumental for market development.” Those segments are the domain of traditional PLCs.
Much has been made in recent times about the impending demise of PLCs, expected to meet their end as the inexorable digital advance renders them obsolete with the advent of process automation controllers (PACs) and more advanced computer-based controls.
From the bottom up
Chris Elston, senior controls engineer at Fort Wayne, Indiana-based Yamaha Robotics, says that PLCs remain extremely relevant. “Probably 95% of machine builders still use PLCs as the controller of choice when they design a piece of machinery,” he says. “There really aren’t a lot of people out there who have switched over to something like PACs or PC-based control or anything of that nature.”
One of the reasons there hasn’t been an overwhelming rush to implement new control technology at the plant level is that many end users aren’t positioned to support it at the business end of things. “It can be boiled down to this: There’s a lot of skill set out there in the manufacturing industry, particularly with maintenance personnel or automation technicians, that is oriented to using ladder logic,” says Elston. “Most of them don’t understand a scripted language, so they are comfortable with working with PLCs. It’s a workforce issue at that level.”
Don Fitchett, president of St. Louis, Missouri-based Business Industrial Network (BIN), underscores this point (Figure 1). “On the automation side, a lot of OEMs want to push ‘the end of the PLC’ idea; but it’s not going to be the end because the end users drive the market,” he says.
Fitchett compares the current situation to the vendors’ introduction of soft PLCs two decades ago. “When the industry came out with soft PLCs and pushed that approach, end users went out and bought any old computer instead of industrial computers. So when things collapsed, they pointed the finger at soft PLCs and went back to legacy PLCs,” he says. “Even though vendors still sell soft PLCs, they’re not pushed anymore because end users pushed back. A similar situation exists with the process automation controller and other new technologies for the entire plant. They’re not user-friendly for maintenance personnel.”
The fact that manufacturers are finding the depth of the skilled labor pool a significant issue at this time only increases the impact of bottom-up resistance to switching out PLCs. “It’s really an issue of education, and also a generational one,” notes Elston. “Many machine builders are really cutting edge, but the issue with adoption is one of support after the fact. There is always a lag time between builders and users, and end users are typically reluctant to change control platforms. Maintenance personnel will even put PLCs back after they are switched out. They’ve been doing that for years because the PLC is something they have deep experience with and understand.”
“PLCs have been around for a long time,” explains Kevin Romer, product manager at Advantech America. “They work. They get the job done. There are a lot of people in the field that have familiarity with PLCs and know how to use them, so it’s not surprising that they are so broadly applied in industrial automation.”
• 80% of PLCs are used in small applications (1 to 128 I/O points)
• 78% of PLC I/O is digital
• 80% of PLC application challenges are solved with a set of 20 ladder-logic instructions.
These statistics support what some have called an 80/20 rule: if 80% of applications incorporate simple digital and analog control, the boundaries of control applications are being pushed by a 20% minority. This ratio acts to preserve the viability of traditional PLCs.