Since the days of Gutenberg — and through centuries of technological evolution — printing has been regarded as a craft as well as a manufacturing process. The discriminating eye and mechanical knowledge of a seasoned press operator have been indispensable for achieving maximum press performance. However, over the last 20 years or so, the printing industry has seen declining numbers of experienced press operators as they age and retire with too few replacements for them. Not enough vocational schools offer the level of training required, and government-incentivized Registered Apprenticeship programs have gotten underway only recently. Additionally, with the digital revolution, public perceptions have changed. Younger people entering the job market today are more likely to think of a career in graphic arts as something more in the realm of computer-based design than running a 12-color offset press with UV capabilities.
The advance of automation has been an effective way to close this skills gap. Introduced to enhance purely mechanical speed and efficiencies, automation on offset printing presses first included processes like automatic sheet size adjustment, automated plate-changing and wash-up. Currently, however, automation is taking on tasks that could only be done before by a highly skilled press operator — including critical color matching and sustaining ink density and color levels through an entire press run. The use of artificial intelligence (AI) allows for machine learning, so that press performance will continue to improve without operator intervention.
Newer technologies enable integration between the press and post-press processes, like bindery and finishing, in order to automate the entire package manufacturing process across the plant. By collecting and routing data to the cloud, managers can check the status of production remotely on their desktops or smartphones.
Electronic Vision Revisited
The concept of electronic vision — the use of on-press cameras for quality control — is not brand new, but it’s being used in innovative ways in package printing. The key idea is that an electronic device is reliably and predictably checking every sheet printed for defects without discrimination. Technically, cameras photograph every sheet that’s being printed while it’s still in the press but after all the printing has taken place. These electronic images are compared to a master printed sheet that was already approved or a PDF or TIFF electronic file that generated the plate. When electronic vision finds deviations, it immediately reports where the issue is on the sheet and the type of problem and the sheet number (if inkjet numbering is used). Simultaneously, it can either tab the delivery load or automatically sort the sheets if a double delivery is employed. In the future, it may even make its own corrections.
For example, imagine a job with labels imposed 50-up on a single sheet. Of those 50 labels, one may have a hickey and another may be missing a single letter of text in small font. In days past, while an experienced press operator might catch these errors, the job will more than likely be run to completion and only then would bad labels be flagged or removed as the work moves, such as to the folder/gluer. In the automated print process of today, an on-press electronic vision system would detect the errors as soon as the defect occurs and notify prepress to make the corrections right away. This ensures quality, reduces waste and improves efficiency by eliminating the need to correct the errors post-press.
In addition to checking for image problems, electronic vision can also manage the color of the piece using closed loop color control. In this case, the cameras read the color bar and compare that data to target densities, or Delta E. It continually and automatically adjusts the ink keys to keep the job running in the desired color space. Again, this type of automation improves efficiencies, reduces waste and maintains a strict consistency to ensure quality throughout the press run.
The Big Picture
In today’s package printing, jobs typically flow electronically in and out of prepress, the plates are made and the data electronically flows out to press. For efficiency and in keeping with priorities, the pressroom manager may group all the jobs of the same sheet size, or maybe the same PMS color sequence with the plan to run all these jobs before having to wash-up a unit. Or there may be a delivery issue when three customers need their jobs immediately, so that work will go on press first.
In fully automated package printing, the software knows how to organize the jobs for the day’s run and will line them up into a logical sequence based on designated priorities and efficiency. It will then set the makeready and the wash-up steps uniquely for each job. The automated press and software will do this automatically without relying on the press operator.
After printing just 20 sheets of the first job, ink density is already stabilized and the camera can begin checking for defects, comparing every sheet to the master PDF or approved sheet. The camera is not missing anything; it hasn’t detected any scratches on the plates or found any hickeys or other print problems, and it has already put the job in precise registration. When the printed sheets reach this quality level, the counters are engaged and the press is automatically adjusting the ink keys, keeping the color where it should be throughout the run. If anything goes wrong, the operator will be notified and the display on the back screen of the console will graphically show the location of the defect on the sheet while the load is automatically tagged. Then, when the first job is completed, the next will automatically begin without any lapse in productivity.
A fully automated offset package printing process can deliver several advantages, including addressing the issue of finding experienced press operators. The press and software will be able to make some of the key decisions that had been the responsibility of these operators. And, without discrediting their skill, they are vulnerable to simple human error, while electronic vision and interaction offer a level of accuracy that reduces possible legal exposure for some work, such as pharmaceuticals, and helps improve the satisfaction of the CPG print buyer.
Further potential benefits include consistently high image quality, greater production efficiency and predictability of delivery times, and reduced waste of both time and materials. All of this translates into lowering production costs, so that packaging manufacturers can lower prices and/or improve profitability. Overall, such a level of automation is a winning proposition.