UV Ink Flaking on Coroplast and Maxmetal

[Lindquist]

I have been using a Colorspan 72UVX to print directly to corrugated plastic for the past six years without many problems. Corrugated plastic has been the one non-roll material that I can print on consistently without trouble, but now I've run into an interesting problem (that fortunately does not seem wide spread).

We picked up a small corrugated plastic sign from the field last week and nearly half of the sign is blank. The ink hasn't faded - it appears to have fallen off. There are some areas where you can see the ink cracking. You can flake off pieces with your fingernail.

What would cause this problem? The sign I saw earlier today is not a brand new sign, but we have signs in the field significantly older with no problems. The sign was produced this year for sure - I would guess this past May.

Is it possible that extremely hot weather caused the cracking?

On a similar note, last year we began printing directly to Maxmetal (a brand of aluminum composite panel). It has worked out okay, but the UV ink does not seem to stick well to the surface. Fingernails don't always scratch the ink, but it doesn't take much to scratch it - a razor blade will shave it off completely. Does anyone have advice for making the ink adhere better?

 

[Desert_Signs]

Lamps going out? On our old colorspan, we had a guy bring back a stack of coros we printed. I would have sworn he'd sprayed some kind of solvent on them. The ink was practically bubbling up. They were fine when they left the shop. It ended up being the lamps. They were still on, but they weren't working right to cure the ink.

 

[artbot]

a cured coating completely falling off is usually as sign of coating shrinkage. it basically shrinks, pulls the corners up first then the entire coating displaces itself on a micro level shearing itself off the substrate.

 

[Typestries]

Could easily and number of things like old coro, dirty coro, bad corona treatment, or plasticizer migration as well. What did you change in the system? Your brand of coro by any chance? Your supplier? How many hours on the lamps? Did you check if your lamp glass is clean?


I'm assuming nothing's changed on your ink formula, but that might be a dangerous assumption.

We never got more than 500 hrs or so on our colorspans if it helps.


Since you are having the ACP adhesion/cure issue at the same time, it might be wise to look at your UV energy output.....lamps, glass, reflectors, and the power supply.

 

[SignManiac]

In the past for us it was a case of the lamps starting to go after 500 hours. Just recently we were having some adhesion problems on newer lamps and it turned out to be the glass in front of the lamps. We have been printing a lot of slat wall and we were getting a lot of over spray. The over spray was building up a thin layer of ink on the glass which was blocking the amount of UV curing. After scraping and cleaning all the ink off, the problem was fixed.