Ink adhesion on rotary screen ink

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csn7203
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Joined: Fri Aug 23, 2019 10:34 am

Ink adhesion on rotary screen ink

Post by csn7203 »

Hi all
My name is Craig I've been in printing for roughly 12 years. Lately we have had issues with our uv based ink adhering to rotary screen ink. I'm looking for other solutions to try. Our r/s ink is fuji film and our uv ink is wikoff and its typically coated with inx uv coating kcc10017. Lamps and hours on them are good. When we do our tape test we get more ink off then we would like. Does anyone have any other ideas that i can try out? We run a gallus ecs 340. Our lamps are typically set at 100% power at 25m/min. our typical response to this is that it'll post cure but that is not always the case.

Thanks in advance
Craig
Frank Burgos
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Re: Ink adhesion on rotary screen ink

Post by Frank Burgos »

HI Craig. My name is Frank. Nice to meet you.

A few questions, to get a better picture:

You say the “lately” you’ve had issues. First step is to communicate with both ink suppliers. If there was not an incompatibility before, perhaps something has changed. Get that out of the way.

Have you tried different UV flexo inks or different screen inks ink as a quick test?
Does it happen with every color?
Every station?
Have you tried slowing the press speed down to and even slower speed?
Is the volume of the flexo ink unusually high?

I haven’t asked about treat level, because you’re talking about adhesion of flexo ink-to-screen ink. Post-curing makes me nervous. I’ve seen instances where stuff just happens and the ink won’t cure and it improves a little over time but it’s scary.
csn7203
Posts: 16
Joined: Fri Aug 23, 2019 10:34 am

Re: Ink adhesion on rotary screen ink

Post by csn7203 »

Hi Frank

Thanks for the reply. As of Dec. last year we have switched ink suppliers. We were strictly INX but our company found a huge cost savings by switching to wikoff. This is about the time we started having issues. And Yes our ink supplier is aware of the issue. We thought it was just the wikoff screen ink, so we switched to fuji film r/s ink. Then we thought well its got to be the uv coating, so we went back to INX. But we still have the issue. We have sent samples out for testing with no real conclusion.
The issue is not limited to one particular color, and if your familiar with the Gallus ECS 340, the ink is in a vertical chamber rather then a pan. Depending on the operator, the chamber could most likely be full? I can not say it happens in every station. We do move print stations around if we need too but these things are 300-400 lbs if not more so we move them only when a job requires us to.
I would be happy if you had a contact of someone that also runs the galluse ecs 340. Im not a big fan of this chamber system and we have other issues too, that i would like to figure out.
Frank Burgos
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Re: Ink adhesion on rotary screen ink

Post by Frank Burgos »

Hi Craig,

Sometimes cost is confused with price.

I've seen the Gallus' gravity feed chamber but I have not messed with it. I don't have a contact.

I did some work with a client that has a Nilpeter that also uses gravity-fed chambers. He was using water-based ink and after running just one roll, the print got dirty. We studies this a bit and found a huge increase in viscosity and drop in pH and increase in ink temperature. It was our thinking that the heat was breaking down the ink. It's a small amount of ink and there's friction happening.

Another client has issues with adhesion of flexo UV varnish over flexo UV printed images. They'd start off OK, but in a couple of hours the varnish failed rub tests. Fresh ink would fix it, but it kept coming back. It turns out that they had recently moved their presses and installed fluorescent lighting that had more bulbs and were closer to the print stations than before. The varnish was curing in the pan. A cover placed over the pan fixed it, after two months of challenges.

Maybe there's something in these scenarios that help while on your way to fixing this.
csn7203
Posts: 16
Joined: Fri Aug 23, 2019 10:34 am

Re: Ink adhesion on rotary screen ink

Post by csn7203 »

Thanks for the info Frank. I will do some more digging.
Leadpress
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Joined: Fri Nov 30, 2018 2:12 pm

Re: Ink adhesion on rotary screen ink

Post by Leadpress »

Try switching to Zeller Gmellin Inks. They are the best. Also, Have you done the tape test before and has it worked; if so, what Ink were you using at the time? If this is the first time doing the tape test? Alot of times, if you leave the ink sitting for 45 minutes after printing, it will cure all the way. It just comes off when you're doing the tape test because it isn't fully cured. Do a test and keep the product without tampering with it for about 30 to 40 minutes. But don't do the tape test, do the fingernail test; don't scratch the hell out of it, because eventually, if you scratch hard enough, it will come off, but depending on the product, the customer doesn't even put it through such harsh punishment, if it doesn't require it. Try running slower and determine which station or color isn't curing properly and go from there. Maybe your lamp needs replacing, or your reflectors and your quartzes need to be cleaned.
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