It was the press assistant who noticed it first. About 31,000 feet into the run of frozen food bags for a big supermarket chain he noticed spotted a thin line running through the front side of the bags. Not good. He called the press operator over while bringing the press to a halt. The operator had the production manager on speed dial. The afternoon suddenly got longer.
The problem was a little bit of dried ink that had been snagged by the doctor blade on a spot color roller and was leaving its mark on the work on press, about five inches in from the left edge of the package. There was no quick way to tell how much of the job was damaged, but one way or another, a lot of it would have to be re-run. The production manager, a woman with an accountant’s eyeballs and sense of costs, was not happy.
Anilox scoring is a problem we see all too often on all sizes of flexo presses. It happens in a couple of different ways and the end result—until it is resolved—is never good. In almost every case, though, there are a relatively straightforward ways to address scoring, mostly by taking steps to eliminate or at least reduce the chances of it taking place.
The most common type of scoring is from foreign matter becoming lodged between the doctor blade and the anilox roll. This can be a tiny fragment of dried ink, which stops the blade from doing its job of metering ink on the anilox roll. This leaves some extra ink on the roll that is promptly transferred to the plate and onto the substrate. A clean ink supply aided and abetted by properly filtered ink can prevent errant particles of ink from going where they don’t belong. Yet time and again we see presses with old, thoroughly clogged filters that can actually be a source for ink contamination. Too often we hear that it takes too long to change the filter and that it doesn’t really matter all that much. Or it doesn’t until a few thousand feet of a jobs has to be re-run to correct a printing problem.
The one possible upside is that dried ink is unlikely to eat an anilox roll. That’s the job of a bit of metal spawned by a worn out or damaged doctor blade. Like the tiny bit of dried ink, a fragment of steel becomes trapped between the doctor blade and the anilox roll, where, if you’re lucky, all it will do is put a line on the product you’re printing. If it’s not your lucky day, the bit of steel begins to wear a thin, narrow groove in the ceramic coating of your anilox roll, creating a good reason to write a check for a new roll.
Ideally, the little bit of errant metal should have been caught by a rare earth magnet and/or a good filter, but your accountant argued against the expense of rare earth magnets—which are far stronger than their ordinary counterparts—and the press operators keep saying changing filters is too messy and takes too long. But it probably doesn’t take as long as re-running several thousand feet of a job and is definitely a lot less expensive than trashing a few thousand feet of the laminated substrate the job specified.
Another type of anilox scoring is “burnishing,” which happens when an area of an anilox roll is damaged so that it will no longer lay down ink properly. It’s less common than the problems caused by dried ink or pieces of worn out doctor blades, but the result is the same: wasted time, materials, and the need to do work over.
When I or other Provident Technical Sales Reps visit print shops, we often see the makings of anilox scoring in process. It’s not unusual to find no magnets in use at all, at all, let alone rare-earth magnets, and unfiltered inks are all too common. It’s easy to ignore these best practices because they can seem like extra steps with limited return, but over and again printers tell us all it took was one scored anilox roll to make them believers in these basics of good press and print management.
Other practices are even easier. Be sure to use the correct anilox roll for every job and remember, the doctor blades should just kiss the roll, removing only the amount of ink necessary. Too often blades are set up with too much pressure on a roll, increasing wear on both the consumable blade and the pricey roll. This can be compounded through the use of the least expensive blades available. These tend to wear faster and are more prone to leaving fragments in ink train which, absent magnets and filters, can wind up stuck under a doctor blade.
If nothing else, my colleagues and I recommend adopting a regimen or standard operating procedure of cleaning magnets and filters at least once a day, and even once per shift in busy shops where multiple jobs are running all the time. The time spent is much less than that required to identify and correct an anilox scoring problem. Inks matter, too. Yes, it’s extra work to make sure inks are as clean as possible, but it pays off in print quality and less downtime due to unexpected problems on press.
We know from our visits and conversations with owners of successful flexo shops, that instituting a few best practices can help reduce and even eliminate anilox scoring. It’s all up to you and your team to take the steps to change anilox scoring from a problem to an exclamation of “Score!” when job after job come off your presses error-free.
To learn how Provident’s Technical Sales Reps can help your shop prevent anilox scoring, reach out to me, Sam Benson, and I will connect you with the TSR for your shop. We are Provident and your success is what drives us forward.
By Sam Benson
Technical Sales Representative