Thursday morning. A familiar name of one of his customers appears on the phone display of Marek - Sales Representative of one of the flexographic printing companies. They have been cooperating for some time, the customer orders quite a good amount of labels, although Marek knows that the customer orders some of his work from his competitors. Marek picks up the phone and hears a familiar voice in the receiver:
Hi Marek. There is a mega urgent issue. I have pallets of goods practically on the cars, and I don't have labels to wrap them. Our other supplier didn't make it, well, and we have a problem. I am just emailing you the job, and tomorrow the courier will deliver the pre-printed label to you. For when are you able to print it for me? It has to look the same as what I'm sending you!
An impossible situation? Yes... but only in the part involving a phone call from a customer. In today's market reality, it's the Brands that have to make a lot of phone calls, use the range of their sales skills, to make the customer want to transfer to them the work they are currently printing somewhere else. Whether it is fortuitous situations, commercial conditions, technological capabilities or the need for a minimum of two suppliers, the practice of transferring or printing the same job in parallel at several locations is not unusual. Logistical security, understood as the need to ensure continuity of production, or the international nature of print ordering entities, often even force the need to have two or more suppliers printing the same job, at the same time. The customer's requirements for the end result are unequivocal. Both products are expected to look identical. The label printed at Printer A is to be the same as the one printed at Printer B, and vice versa.
So, using an example from real life, let's take a look at the situation our mystery shopper found himself in, transferring his work to Mark's print shop, and what Mark should pay attention to in order to meet the customer's expectations. Some time ago, we were approached by a customer printing the same packaging in several different places, receiving several different end results. The client asked us to analyze the reasons for the color differences on the two reprints.
The photos used in this article are comparison photos showing the same areas on both packaging. After analyzing the reprints and both packaging production processes, we identified the following causes as sources of possible color differences on the two reprints.
Reason 1: Differences due to graphic design preparation for printing and proof preparation.
Although in theory both printers worked on the same files, internally they adapted them to the requirements of flexographic printing in a way that was specific to themselves (read their printing process). In the case of using an external company to adapt the design and/or prepare printing plates , it is necessary to have up-to-date color profiles made in accordance with the principles of printing standardization, i.e. dedicated for a given printing substrate, for a given printing machine, for the printing Printing inks specific to the work of Aniloxes and Printing inks .
Also of no small importance at this stage is the method of proof preparation and the measuring devices used in the process. If they are used at all. Calibration of monitors in the context of the above is a necessary requirement.
Errors or differences made at this stage are very difficult (if possible at all) to make up for during printing. The need for such catching up is time- and therefore cost-intensive.
Cause 2: Differences due to the printing plates used, how they were prepared, and the equipment on which they were prepared.
Plate is not equal to plate. Despite the equal quality level of plates available on the market today, the use of different plates in the printing process of the same label or packaging can affect their final appearance. I am mainly referring to the way the plates transfer ink to the substrate (transfer Printing inks), the ability to reproduce the minimum printing points or, finally, the strength itself in printing longer runs. Even assuming that we make two different plates from the same file, it is very likely that printing without any calibration (i.e. color profiles, dot gain curves, etc.) we will get two different final results. It is also important to correctly select the rasterization parameters of a given plate for the nature of the production.
Poorly chosen plate preparation parameters can translate into reduced plate life, abrasion of small print dots, and consequently the formation of color differences between the beginning and middle and end of printing.
The quality condition of plate processing equipment is not insignificant in this puzzle. Old, unmaintained equipment or equipment with parameters unsuited to processing modern CtP plates can cause the same problems as poorly selected plate preparation parameters.
Cause 3: Differences due to the use of paints from different suppliers, different paint formulations.
Many times we encounter a situation where a given custom color is mixed by operators "for the moment". The absence of any ink formulas makes it impossible to reproduce them in the future, should the need arise.
Also, with CMYK process inks from different manufacturers, there may be color differences due to different pigmentation of Printing inks. It is advisable to use one type of ink for a given job, especially when the calibration process I mentioned in "Reason 1" was carried out with the type/manufacturer of Printing inks mind.
Cause 4: Differences due to the raster rollers used and/or their condition.
The raster roller is the heart of the printing machine. It is responsible for delivering a well-defined amount of Printing inks to the printing plates . Therefore, the quality of the raster roller has a colossal impact on the printing quality. We match the Anilox Volume to the amount of Printing inks we want to apply to the material. Depending on the linetype of the job, we also select the anilox linetype. Errors or differences in the selection of both parameters (i.e., linature and volume) of the raster roller result in differences in printing. And when combined with inks from different suppliers, they create a difficult to control combination of causes of possible problems in printing.
Even well-chosen parameters of raster rollers won't help anything when the actual condition of a given roller is far from its rated condition. The photo below shows the same roller before and after cleaning.
The above measurements illustrate the difference in raster roller cell capacity before and after washing. The difference indicated in the measurement is more than 30%. Such a large difference between what is written in the roller's technology sheet and the printing results you actually get cannot but affect the color of the reprint. Thus, this is one of the possible causes of color differences in printing. Standardization of anilox rollers and their regular inspection is a very important factor, especially when dealing with such a "delicate" subject as the need to obtain the same printing results as a competing printer.
We are nearing the end of our analysis. Both Mark and his client should reflect on the above aspects to avoid mistakes already made by others.
Aha...... You are probably wondering where half of the reason I wrote about in the title of the article went. Well, that half is a mix of all those mentioned above and those not addressed in this article. Flexographic printing is a complex process involving many interconnected aspects. How to survive this thicket? How to prevent the situations described above?
The answer is simple: by applying control procedures at each stage, standardizing the entire process to the point of pain. Introduce checkpoints in the processes, measure and control key aspects of them, so that you know the outcome of the action even before it starts. But that's a topic for another article......
