What You Don’t Know about Ink Systems Part 3
Episode 3: End Seals
Chances are you probably don’t spend much time thinking about end seals, those little plugs of foam, rubber or felt set into the ends of your ink trays. Then you lose half a shift or more of production because one of them decides to go south and spoil your afternoon.
You don’t think about them because most of the time, the seals just do their job. Then one day, if you’re lucky, a seal starts dripping, giving you a heads-up that its best days are behind it. Or if luck isn’t with you, one or more seals blow out, perhaps spectacularly, spewing ink in every direction. On a narrow web label press a seal failure is just really messy, but when it happens on an upper ink tray on a big CI press it shuts down the entire operation for a few hours while the press and floor are cleaned up. Then the press is re-webbed, damaged materials are thrown away, and the job restarted. It makes for a long afternoon—and is a painful way to burn through a few hours of press time—at several hundred dollars per hour—plus a few gallons of ink at up to $10 a pound.
Add that cost up over half a dozen seal blowouts a year and the damage can easily amount to several thousand dollars, all because a consumable part—costing between from fifty cents and four dollars—failed. Does any of this sound familiar?
“We hear about one blow out per week,” says Randy Carter, senior technical sales representative at Provident Group. “There are a lot of presses out there, so that hardly means that seals are failing all the time, but it highlights that seal failure is common and that some printers and converters don’t always appreciate the larger costs of a seal failures.”
“Printers and converters don’t want to take a press down just to replace seals that seem to be doing the job,” continues Carter. “They wait until a shift change or a press is on its next scheduled maintenance.”
At first glance, the logical approach of “if it’s not broken, don’t fix it” makes sense because it minimizes downtime, but it can actually be detrimental to an operation. The problem is that seals don’t fail when a press isn’t running and often fail with no warning. So if replacement isn’t part of scheduled maintenance routine they can be easy to overlook, which can lead to failure when the press is running.
Adding complexity to an apparently simple topic, end seals are anything but generic. They vary by material, density, longevity, type of press, shape, expected speed and ink chamber pressures, and more. And, some, like those from Provident Group, can be customized to your presses. This apparent simplicity makes it easy to change jobs on a press but leave seals in place that were fine for the 15,000-foot job that just finished but are not at all suited for the 120,000-foot job with different rolls and that’s running next.
To minimize this risk, some shops make it a standard practice to change end seals after every job, once per shift, or at some other interval when a press is down for scheduled maintenance. Others replace seals and doctor blades at the same time to minimize the chance of problems in their ink systems. Being proactive about these basic consumables is one of the keys to productivity and efficiency, and helps minimize the chance of problems that cost money due to unplaned downtime.
“If shops can do an ink chamber rebuild say, once a week: doctor blade and end seal, and do any other required maintenance at the same time they can ‘double-dip’ on normal press downtime and better control risk,” says Carter. “It’s a matter of spending a couple hours of what is already scheduled downtime versus up to four hours of unscheduled time when a seal blows out. It immediately pays for the few dollars the seals cost.”
>>Read Episode 1 on Shrinking Cell Volumes
>>Read Episode 2 on Cleaning Anilox Rolls
