Best Practices: Proper Plate Practices

You may be thinking, “How hard could it be to clean and maintain flexo plates? I know what I’m doing.” Well, you might be surprised to hear that it’s not as simple as it seems. Ensuring flexo plates are ready for reuse requires diligence in the cleaning and maintenance processes, with adherence to a general set of guidelines. 

Know When to Clean Your Plate

Proper plate care will lead to cost savings in the long run. It will reduce the need for repeated plate manufacturing and will provide tighter registration during production. So the first rule of thumb is to clean your plates immediately when they are removed from the cylinder.

DuPont Cyrel Easy flexographic printing plate technology increases efficiency by removing flat top dot processing. With proper care and maintenance, printers will see improved plate performance.

“I’ve seen some printers leave ink on their plates and assume they will clean them later, but that isn’t good in the long term,” Jessica Harrell, technologies manager at Anderson & Vreeland, says.

Additionally, it is important that the plate is clean before it is put on press. Jim Kulhanek, senior technical service consultant at DuPont, explains that if a plate isn’t clean before running a job, particles can get trapped under the ink, making it impossible to remove. Establishing that ink and residue have been removed prior to use will ensure the best ink transfer possible.

Know How to Clean Your Plate

Even converters who understand the importance of plate cleaning often don’t know what the best materials to use are. Both Harrell and Kulhanek explain that one of the worst is nylon.

“A lot of printers have used pantyhose or nylon mesh to clean ink off of plates and that’s actually one of the worst things you can use,” Harrell says. “Use either a horsehair brush or something really soft. And no tooth brushes.”

Kulhanek suggests using a sponge or a lint-free rag — nothing abrasive or coarse. He explains that different materials can have different impacts on the integrity of the plate.

“I’ve seen more customers in recent years asking for smaller and smaller dots,” he says. “With higher resolution screen, we’re now printing some of the smallest dots we have ever seen. If you use something coarse, the dots are going to come off.”

As important as it is to know what material to use, it’s equally important to know what cleaning agent to use. Although Kulhanek and Harrell recommend using 100% alcohol, they both advocate for plate testing before attempting to use and clean them. Performing a swell test can help to determine if a cleaning agent will alter or damage the plate in any way during the cleaning process.

“Unfortunately, I’ve found that there are a lot of chemicals out there that do a great job of cleaning the plates,” Kulhanek says. “What I’ve also found is that some of those chemicals have a lot in them that is very similar to the printing plate and they can start to dissolve or disintegrate the plate. The chemical will actually absorb into the plate and then you will have problems down the road.”

As automation becomes increasingly important, automated plate cleaners have become an enticing option. But, with auto cleaners come different required cleaning solutions. It is imperative to know what type of cleaner is best when paired with the type of ink being used.

“Auto cleaners have different solutions that can be customized for the type of ink being used,” Harrell explains. “If you optimize your cleaning solutions to the ink type, you’re more likely to remove all of the ink and residue.”

Harrell continues by explaining that optimization ensures that the automated plate cleaner is working at its full potential; otherwise it will not work as well. 

Delegating plate cleaning responsibility can be another issue that arises in the pressroom. Harrell says that many operators procrastinate when cleaning plates because they want to continue with output production and they want to get jobs on the press, rather than taking the time to immediately clean them. She suggests it might be wise to find an intern to clean plates so that production can continue, although, she says that it is necessary to make sure they are properly educated first.

Know How to Store Your Plates

The job, however, isn’t finished once the plate is cleaned. You need to make sure that the plates are stored properly. If they are not stored in a stable environment, they may slowly break down when not in use.

Kulhanek suggests interweaving foam between each of the plates and storing them flat — in stacks no more than 6˝ high. He explains that because some of the plates on the market today feature a higher durometer, they can actually begin to emboss or make indentations on the other plates.

Kulhanek explains that although many of the automated plate cleaners work very well, some of the cleaners used with them include oils, which are hard to dry. Leaving the plates wet or with oil still on them when they are layered in storage can lead to solvent retention.

“If [plates] are not given enough time to dry, the oil is basically trapped within the plates and there will be a moisture barrier,” he says. “The barrier will begin to dissolve the printing plates so you may have a reduction in plate caliber.”

Harrell explains that it is also important to inspect the plates prior to storage. Making sure that the plates are clean and dry before they are put away can reduce further damage.

While in storage, it’s necessary that the plates be kept away from light sources, extreme temperatures — room temperature is best, Kulhanek explains — open doors, sources of ozone, vents and electrical discharge.

When in Doubt ... Just Ask

Although many of the general rules can be used to clean and maintain flexo plates, it doesn’t hurt to ask the experts. Harrell suggests always asking the plate manufacturers before use, to make sure that you know the best solutions for each individual plate.

“Ask your vendors. Ask your plate companies. Ask your ink companies,” Kulhanek says. “There is a lot of expertise out there, you just need to tap into it.”