Ink not drying, PLEASE HELP !!

[Bassfishr]

Several months ago everything was running fine and then BANG ! We have 2 Metronic Opticard 200 offset presses. We are printing on PVC like credit cards. The problem we are having is the backs, we have Toyo waterless UV black ink & 2 UV dryers. After the process you can just scratch the print right off, but if you run it thru more dryers it dries just fine. This running everything thru the press twice is just killing us. PLEASE HELP ! !

[meddington]

Obviously the ink isn't curing, eh? You've printed successfully on this substrate prior? Perhaps you need to verify that the lamps are optimal.

[meddington]

Thanks for the reply ! The dryer performance is my conclusion also. We have tried at least 5 different inks, tested several different substrate mfgs, and even used several different bulb makers in the U.S., then ordered the original bulbs from Germany. Which were sent back because someone said they were defective. Like other posts I have read in this community, we also have a "GENIUS" that in my opinion has exausted every theory more than once, but just isn't ever wrong even thought he only has 1 year in this field. In your opinion could it be that the dryers just aren't getting to the optimal temp ?
Our busy season will be on top of us in a few months and I want to get this fixed before it's too late.

Maybe not so much temp, but perhaps the energy level or irradiance or focus of the lamp output is weak (if I understand your situation correctly). Not really a uv printer here, but if you had been using this ink successfully in the past, I would suggest you have a press tech check the lamp output, and if that is optimal, get the ink rep involved.

[Bassfishr]

Thanks, that is exactly what I have suggested. I have been in contact with a curing company in Florida and you have stated pretty much the same as they did. In your opinion, if I had a radiometer & had my lamp measurements, I could contact the ink mfg. & go from there ? This should help be on my way to the solution to my problem. Right ? ?

[meddington]

Thanks, that is exactly what I have suggested. I have been in contact with a curing company in Florida and you have stated pretty much the same as they did. In your opinion, if I had a radiometer & had my lamp measurements, I could contact the ink mfg. & go from there ? This should help be on my way to the solution to my problem. Right ? ?

Again, I'm no expert, but I think focus and position is important as well, even if lamp output measures well. Some lamps might need finer focused light than others. Maybe someone else can chime in, but I think you need a tech onsite to evaluate. One more thing...are you printing the same ink film thickness as before? Thicker ink might take longer to cure?

[dimitri]

I do not know much about printing on plastics, but apart from the lamps, you got to make sure that you maintain your reflectors clean. These are actually more important, since most of the UV light comes from them to the ink/substrate. You could use the RadTech or Tape-Reader devide to make measurements of UV intensity.

You need to put your ink supplier and lamp/reflector supplier on board to figure out all the little details. See if the ink batches were defective to begin with. They might have forgotten to use photoinitiator or used less than needed... just make sure the ink is fine.

As a general rule, also try to keep your density as low as possible and your water levels as low as possible. Thicker film might be only partially cured... once it leaves the press that's it!
Speed is a factor as well.
In case you are using coatings, make sure you are drying the ink prior to the coating.

[Bassfishr]

Thanks for the reply Dimitri. I've put new reflectors in, and have also cut the ink film back as far as I can and it still print. We have used several different inks & even had a couple of people tell us to mix blk/cyan at a 80/10 ratio to help with the drying issue. I still think its a dryer issue since it was working previously back until October & it was like someone flipped a switch, it just quit one day & hasn't been the same since. If I run them thru the press with 4 or 5 dryers on it cures perfectly. Just like it did before. This is getting rediculous. I just want a fix so my job will be easier.

[Johnston Collins]

sounds like the strength of the uv lamps is not strong enough.
how old are the lamps?
how many hours have they been operating?
the supplier should have given you info on the lifetime of the lamps

[Johnston Collins]

JC, thats what I think it is. We have gotten several different bulbs from several different mfgs. None worked but the ones that came closest were the originals from Germany. These are the ones the "GENIUS" sent back and said they weren't any good, just because one of my co-workers who has been printing for 20+ years ordered them. Everyday is a power struggle...... ____UPDATE !! ---->
We were going to get a curing company out of Florida to come and see if they could resolve the problem, but the powers that be didn't want to step on the local "GENIUS' " toes. So were still doing double the work. My thing is you can look at the bottom of the dryers as the cards go thru & the bulbs don't look as bright as the once did. *** The good part is one of the big dogs has contacted Metronic & they are supposed to come from Germany very soon... I really appreciate everyone who has replyed to my post & good luck in your printing adventures. I've been printing for a little over a year & every day is a adventure to me...

if possible, rather than 2 passes, slow the press down?

[arfamoe]

Have you tried what is reffered to as 'Doped' lamps, these contain iron instead of mercury so work off of a much broader UV spectrum and work well for curing problem colors like Dark blues, blacks and Opaque whites. Just a suggestion.