Most of us probably think that printing is nothing more than preparing words and pictures that can then be printed onto paper. Because of this simplicity we might believe that every printing will be same and, so long as the origination work has been checked and approved there will be no need to inspect each item as it comes off the printing press.
However, if you really think about it, you will conclude that this 100% correct repeatability is not always the case and even approaching it might be difficult. Think about something that is probably within most people’s personal experience with such as computer printers and photocopying machines. It is not unusual to wish to make multiple copies (let’s say 10 or more). You have the document in the computer and have proof read it thoroughly; or you have a hard copy and wish to copy it; either way, you set up your print/copy run and then walk away to get a cup of coffee or something.
On your return you expect to see a finished set of perfect duplicates but – something has gone badly wrong. Maybe the first few copies are perfect but then colors begin to change, words get fainter, the printing has become skewed on the paper, the paper is torn. There are a veritable host of printer, ink, copier, toner or paper related problems that might ruin your simple print run.
Had you been standing beside the machine and checking each copy as it came out, you could have stopped the run at first sight of a problem, taken corrective action and then continued successfully to the end. At worst, you might have wasted one piece of paper. Because you were conduct a printing inspection you saved a lot of paper and wasted time.
Printing Inspection On A Big Scale
Companies printing reading material such as books, magazines and newspapers as well as those that are printing packaging materials and/or labels, bar codes, etc will be printing in bulk. In their case, is it possible for a human inspector to check each piece as it comes off the printer and before the next one follows it? And, if something has gone wrong within the printer or the big roll of material (termed a web) to be printed on and then cut to size, how much web will pass through the printer before the fault is spotted and the print run stopped to avoid further waste?
On this scale, printing inspection has to rely on technology. This will usually take the form of computer controlled video cameras that can spot problems inside the printer, report them to programmed software that will either warn operators or actually stop the printing process.