Definition of Process Control: An engineering discipline that deals with architectures, mechanisms and algorithms for maintaining the output of specific process within a desired range.
Process Control in our Daily Lives
How do we translate this definition into something we can understand in our daily lives? When talking about process control I’ve been asking people this question; “Can you drive down a straight stretch of road with your eyes closed?” I think we all know the answer to this question. Even though the road is straight, the answer is no.
So why can’t we close our eyes? We are using our eyes to constantly monitor our location on the road. If we don’t, we will certainly run off the road. Our eyes are taking ‘measurements’ of our position in the lane on the road. Our brain then evaluates this information and tells our arms to move the steering wheel to the left or right to keep us within tolerance (in our lane on the road). This is process control. We are controlling the process of driving down the road. The goal being to get from point A to point B without running off the road.
This is process control in our daily lives. We are using process control to drive our cars down the road. We are constantly taking in information, evaluating it, and then taking corrective action to keep our cars in the middle of our lane. Without this seemingly automatic observation, evaluation, and taking action we wouldn’t be able to drive a car without running off the road or hitting something.
What happens if we close our eyes? We stop one of the fundamental steps in process control; we stop observing (measuring). We have nothing to evaluate, and therefore can’t take action. We can’t keep the car in the lane on the road.
Process Control in the Printing Process
So let’s adapt this concept to the printing process. When an offset press operator pulls a sheet out of the press and runs it through their scanning spectrophotometer at the press console, what are they doing? They are measuring how the press is doing (taking in information). Once the sheet is measured the results are evaluated to show the operator how the press is doing, and then the operator takes action to keep the press within some set tolerance. Just like driving down that straight stretch of road, the press operator is using process control. Press operators have been doing this for quite some time, with or without the newer scanning spectrophotometers.
Let’s take this a step further. The press operator has finished the job and the last sheet looks the same as the first. Months go by as they continue to run jobs and stay basically within ‘tolerance’ to the proof. What they don’t notice for some time is that it is becoming more and more difficult to match the proof. What they aren’t measuring is how the press performs over time. Just because there have been a number of successful jobs, doesn’t mean the press is printing consistently on an ongoing basis.
What happened? Well, the printing process is not stable. It is subject to multiple physical and environmental variables that affect how the printed sheet looks. This would be akin to driving down a straight stretch of road and all of a sudden a strong cross wind starts blowing. You, of course, automatically compensate for this as you see the car moving toward the side of your lane. You’ve adapted to the variability of the wind hitting your car. What the press operator doesn’t see is that changes in temperature and humidity in the pressroom change how the press prints. They are slowly correcting for this on a job-by-job basis. At some point the change is too much (from season to season) and corrections have to be made to get the press back on track. This, of course, is just one of many variables that affect printing over time.
Process Control: Keeping you safe while driving and your printing results consistent day in and day out.
To control any process you must:
- Take action
So why are you running your printing business with your eyes closed? Keep your eye on how your printing devices print and you will reap the benefits of using process control to reduce waste and improve consistency. Your pocketbook will see the difference and so will your customers.