The simple reality of anilox rolls is that their proper care can make or break production. It is essential to understand the greatest issues facing your rolls and what steps are necessary to protect these assets for the long haul. Far too often we see capital wasted because of improper methods of cleaning or handling that damage the surface of a roll and require its replacement. With a firm comprehension of product selection, handling, and well-timed maintenance, most of this damage can be tightly managed or eliminated entirely. While this is true across the board for anilox roll care, it is especially true for avoiding the detriment of score lines.
There are two types of score lines in the printing world: abrasive and depository. While both cause issues with obtaining optimal print, both can be prevented indefinitely. Score lines are most often caused by improper handling due to inexperience, a misunderstanding of their specifications, or a lack of quality maintenance. With the right education and training, anilox rolls can live a long and productive life. But how do we get that life out of them and avoid score lines? The first step is understanding the how and the why of the two types of score lines.
Abrasion is the process of wearing down the surface material. In terms of anilox, this means that the anilox roll cells are being eroded by some type of friction. These abrasion score lines are seen in areas where the cells have been subject to increased rubbing through abnormal use. The cell walls have actually been worn down from the very top and created a valley in comparison to the surrounding cells.
You likely know that a depository is somewhere things are stored. But when it comes to our anilox rolls, this takes on a far different meaning than storing a priceless heirloom in a bank vault. This is not what we want for our anilox roll cells because it means that the cells are being filled with soft metal debris or dried ink. The more ink that remains in the cell means the less ink that makes it onto the product. Pamarco research tells us that there is a maximum of 40% making it through to the substrate already, so depository score lines are causing that number to continually go down as the cells fill up.
Depository and abrasion score lines can both be caused by several things: improper chamber alignment, lack of filtration, or even an issue with a poorly pre-engraved anilox roll surface. In order to determine which of these issues you’re facing and to figure out the best way to avoid them, we’ll look at each of these three in turn.
Improper chamber alignment consistently leads to increased pressure and deflection. This creates an area for debris to lodge under or behind the blade. In other words, depository score lines occur because the pressure is uneven and this creates pockets in which that ink or soft metal love to hide. This improper alignment also causes abrasion score lines because the increased pressure results in certain areas being subject to higher levels of pressure than others, creating dips in the cell walls.
Lack of filtration is the most common way that debris is introduced into the ink system. There are a multitude of sources of debris and isolating the source is often like hunting for a needle in a haystack. The three likely culprits introducing metal into your ink system are doctor blade materials from over-pressing, solvent lines, or work-off ink. It may take some time to find, but I assure you, it’s in there.
The last possibility for the cause of score lines can actually be an issue with the anilox roll itself, rather than maintenance or handling. Poor, pre-engraved surface finishes lead to poor-quality engravings. Peaks and channeling in the engraving create a situation where these high, thin areas of ceramic can be easily and quickly sheared off. Once this ceramic material is introduced into the doctoring system, it will quickly score the entire roll. Generally, if the scoring is related to a poorly-made anilox roll, it will score within the first twenty-four hours of use and the entire surface will be scored.
That’s the how and the why of score lines, but what about the solutions and prevention? There are many possible solution routes to consider, but there are eight that I believe carry the most weight.
EIGHT THAT CARRY THE MOST WEIGHT
- Make problem elimination a priority. If you aren’t trying to solve the problem, it won’t be solved. Period.
- Identify the type of score line
- Check your chamber blade alignment
- Have used blades analyzed
- Install a filtration system with strong rare earth magnets
- Inspect all tributaries to the ink system
- Re-train and review housekeeping
- Call your anilox supplier and yell at him
Pamarco has made great anilox roll advancements and currently produces rolls that have exemplary wear and tear resistance, but even the best anilox cannot stand up to the friction of long-lasting impact. It is important to maintain your anilox rolls on a day-to-day basis and to set systems in place that will help you prevent scoring and a host of other problems that stem from overlooking maintenance. Don’t let poor anilox surfaces hinder your production groove when there is so much opportunity to prevent them.