I’ve worked in numerous plants and visited dozens of others. All of them had something in common: their control systems were completely driven by Programmable Logic Controllers or more commonly called PLCs. Although these systems are extremely common in manufacturing, you don’t see them elsewhere. It is thus very interesting to discuss some of the advantages which these controllers bring to the table as opposed to other methods of control. Having worked in the field, I can provide a real perspective as to why you’d want to use a PLC instead of a PC driven solution despite a higher cost.
A PLC built by a reputable manufacturer (Rockwell, Siemens, Mitsubishi, etc.) should last for decades and reliably drive your process twenty four hours a day all year around. These OEMs (Original Equipment Manufacturers) went to great lengths to make sure that their controllers are able to withstand changes in temperature, voltage spikes, power blimps, current surges, humidity and more. I’ve worked with PLCs from over thirty years ago. They drive machinery like clockwork without any issues booting up or in run; they simply don’t fail. A lot of work and thought went into their design; everything from protective circuits to robust mechanical components is used.
Maintenance is a major component of any manufacturing organization. Not only does it keep the equipment running, but it’s also responsible for fixing breakdowns as fast as possible. A reliable PLC along with its platform is crucial to achieve both of those goals. Not only can you easily swap the plug-and-play components of a PLC rack, but you can easily obtain information about the status of your modules before you even connect to it. A skilled technician can assess the problem from the electrical panel and swap our the faulty components in minutes. There’s no need for intricate debugging tools, software reconfigurations and expensive downtime caused by a malfunction.
Every organization drives continuous improvements when it comes to their process. As someone who has participated in speed up and new development projects, I can assure you that a robust and expandable control system plays a vital role when it comes to such projects. It’s simple to add a new Input/Output module, a servo drive or any other capability to an existing PLC solution. In contrast to some other solutions, there’s rarely any need to re-engineer the hardware.
PLC platforms can be modified at any time without the interruption of a process. This feature was introduced in the last decade and allows one to make assessments of how the process is performing, add or remove features and to fix bugs. In fact, it is extremely difficult to take the time to shut down a production process due to business reason and this is where a solid PLC platform comes in. A skilled engineer can make most (certain changes do require a PLC Download) programming implementations on a live PLC without incurring downtime that’s often difficult to justify.
Although in the ideal world, no one would touch a PLC after it has been put in place, there is a constant need to add features, remove bugs and to troubleshoot the system. This is possible due to the fact that most platforms are completely standard. This begins with the fact that there is a number of communication protocols the devices might use, to the voltage levels on the hardware, to the standard ways to implement certain bits of code. Everything is highly standardized in order to allow anyone to come in with a good understanding of what’s going on in a particular system.
Each manufacturer has their own opinion on which brand of PLCs they would prefer. Although we will leave that discussion for another day, they all agree that a Programmable Logic Controller or PLC is the ideal solution for their manufacturing needs. It has a longer life expectancy then most other systems, comes in a reliable platform allowing live troubleshooting & replacements, gives the engineering department an easy way to expand on the platform and last, but not least makes it easy for anyone to get online and begin working on the existing code.