A Litte Care Goes a Long Way in Flexo Plate Maintenance
Flexo plates have a tough job, whirring around on a print cylinder, covered in ink and repeatedly transferring an image to a substrate. But to make sure these plates can withstand the high-impact nature of printing, they require delicate care and maintenance.
According to Jason Cagle, application development specialist for MacDermid Graphics Solutions, two of the most common missteps in plate cleaning and maintenance are the use of aggressive chemicals instead of those approved for plate cleaning, along with using a coarse rag or brush to clean plates, which can lead to damage.
When it comes to chemicals, Cagle explains there are a couple different avenues printers and converters can explore to determine if they’re using a proper solution. First, he recommends printers check with their plate supplier, as they will typically maintain a list of approved chemicals. Additionally, he states that acquiring chemicals via a flexographic products distributor, rather than looking outside the industry, is also a safe option.
“If you’re going to Home Depot and buying a chemical that is really aggressive, then you run into issues,” he says. “If that’s how you want to approach the situation, we suggest that you reach out to us before using that chemical so we can make sure and approve it.”
In terms of the tool being used to remove ink from a plate, Cagle recommends a natural-hair brush, such as horsehair, which allows ink to be removed without much aggressive scrubbing. Likewise, Rich Emmerling, technical director for Flint Group Flexographic Products, suggests printers not use aggressive cleaning procedures when cleaning plates, which can lead to damage.
“For instance, using shop rags, nylon covered sponges or stiff bristle brushes to clean plates can damage fine elements on the plate, but the use of these is not uncommon to see,” Emmerling says. “It’s important to ask for suggestions from your plate supplier, be that the manufacturer or the distributor.”
Another potential pitfall for printers is in how they remove plates from the cylinder at the conclusion of a print run, Emmerling says. It’s important to utilize extra caution when removing the plate from the cushion tape, so as to not kink the plate backing, or even worse, tear the plate.
“It’s important to take time to remove the plates in an easy fashion,” Emmerling says. “Also, when trimming the plate before mounting, make sure clean cuts are made, especially with the staggered type designs, to prevent any nicks in the polyester backing, which will make the plate much more prone to rip.”
While converters need to pay careful consideration to how they clean their plates, both Cagle and
Emmerling explain that plates can also become damaged in storage, and specific steps should be taken to ensure plates are protected even when they’re not in use.
If plates are being stored “in the round,” meaning they’re still mounted on a sleeve, Emmerling states that it’s important to keep them wrapped in a film, such as polyethylene, to prevent potential damage from ozone or UV lights, which can alter the physical properties of the plates.
Additionally, he explains that if plates are being stacked on top of each other, converters should use a foam or silicone-coated paper interleaf between each plate. Otherwise, he says printers run the risk of plates sticking together or transferring debris from the back of one plate to the printing surface of another.
One common storage misstep that Cagle says he often runs into is printers assuming that if a plate has been cured, that it is no longer vulnerable to heat or UV light. He explains that plates should be stored at temperatures below 100 degrees Fahrenheit, which is typically easy to do, but can become challenging for converters storing plates in the rafters of warehouses in warm climates.
Similarly, Cagle states that even if a plate is cured, it should be stored away from potentially damaging UV rays. He explains that oftentimes when printers are experiencing plate cracking or durability issues, it’s because their plate storage room has skylights or windows that allow UV light to reach the plates.
“That’s a big one,” he says. “If you have a plate storage room that has windows, you want to make sure they’re protected from the UV light. Even though the plate is cured, additional UV light toward that plate is going to deteriorate the life of that plate.”
To avoid these issues, Cagle suggests that printers invest in a film that can be applied to windows to block UV rays. Additionally, he explains that plates can be stored in an envelope or sleeve to block UV light.
While care and maintenance for flexo plates is imperative to achieving the highest quality print, ensuring the plate imager is performing at its best should not be overlooked. According to Rory Marsoun, Esko’s VP of business development, flexo, Americas, there are certain steps that should be taken as part of a “weekly checklist,” to keep an imager at peak performance.
The first item, he says, is keeping the imager in focus. He explains that it’s rare for a digital plate imager’s laser to shift out of alignment, but it’s important to conduct weekly checks just to be certain that the laser’s focus is in place.
Marsoun states that conducting a stain test should also be part of a digital imager user’s weekly checklist. He explains that this test will indicate how well the imager’s laser is removing the black carbon LAMS (laser ablative mask system) layer.
“We want to make sure that our imager is removing that layer adequately,” Marsoun says. “Over time, let’s say the lens gets dirty inside your machine, you might start to see the stain get worse, meaning we’re not removing the LAMS layer completely.”
Marsoun explains that conducting these focus and stain tests equate to “checking the pulse of the machine,” and if those two aspects of an imager are where they should be, users can be assured that their machine is operating properly. However, if these two tests continually lead to unwanted results, he explains that is when a technician should come in to assess the situation.
Additionally, Marsoun explains that Esko and the majority of its customers have a maintenance schedule in place, in which a technician will visit a customer site once or twice per year to perform any needed maintenance, depending on each users’ needs and volume.
“Our technician comes in and does all the maintenance necessary to keep the machine running,” Marsoun says.