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.

 

[povertycow]

Is the ink dry and not trapping to the plastic or does it smudge.It could be a plastic problem and not an ink issue. Have the dyne checked on the plastic.

 

[Sureseal Tech]

re : Ink not drying

re : Ink not drying

Hi there,

From a tech point of view I agree entirely that lamps could be the issue as curing/drying is your problem. You do say that you have tried several different ink suppliers so I would possibly rule out ink issues. I also think that the plastic substrate you are using needs evaluating. Have you tried other suitable plastics.

When problems such as this occur I would generally ask the ink company for help with testing. I would also consider asking the plastic company for assistance. Ink companies are usually quite willing to evaluate problems technically especially if it results in business. They will have a UV lamp which they can use to test curing/drying properties on various plastics. If your current ink supplier is unwilling ask a competitor. Once the ink and plastic has been evaluted under laboratory conditions then you will have a better idea what is causing the problem. If they cure in the lab then your lamps are probably the issue.

I hope this helps, even slightly. If you do have any further questions please get in touch. Glad to help where I can.

John Tierney

 

[Raymond Ramirez]

hummmmm?
Questions

The enviroment of the press area? humidity/and temp

Has the technician inspected the capasitors to the lamps just because the lamps are on doesnt mean the power is smooth. and if the unit do not use caps they probably use a ballast of some sort

let me see if I can explain:

An Ultra-Violet Lamp works by vaporizing mercury within a pressurized quartz tube. In order to start, a high voltage start or spike is applied to the lamp (this is provided by the ignitor). If the voltage spike was successful at vaporizing part of the mercury, the lamp then enters its Warm Up stage.

Warm Up:
As the lamp warms up, more and more mercury vaporizes. This can take a couple of minutes. During this time, the voltage of the lamp starts off very low (around 30-40 volts), while the current that the lamp draws is high (around 20 amps). As more mercury vaporizes, the voltage slowly rises and the current falls. Once the lamp reaches around 80-100 volts, the speed of the voltage rise increases. As the lamp passes approx 250 volts, the lamp achieves ‘Ready’ status.

Ready: When running correctly in High Power, the lamp should run at a voltage of 260-320 volts, at approx 11-13 amps. This will vary slightly from lamp to lamp. In Low Power, the current will drop to around 8 amps and the voltage may drop to around 250 volts. this is based on the Olec 5k. numbers may vary depending on the circuitry and power requirements.


Common Lamp Problems:
Most problems accounted to the lamp aren’t usually the lamps fault. Most of the problems happen with the lamps power circuit, such as faulty ballasts or capacitors, or are a cause of over/ under cooling of the power supplu and/or lamphead

Cooling is very important to a lamp- insufficient cooling and the quartz will swell and breakdown. Once the quartz starts to swell, the lamps normal running voltage will drop and the efficiency of the lamp will decrease. The lamp leads may also suffer from overheating which can melt the insulation and cause a short. If the lamp is overcooled, it may take longer to reach its correct running voltage or may even be ‘blown out’ by the blower. This is when the lamp is unable to sustain an adequate voltage to remain lit. A lamp being overcooled will run at a lower voltage and so will pull a larger current. This larger current will put a strain on the other components in the system.

there are alot of things that need to be looked at. until the intrduction or CTP I had worked on Olec and Nuarcs for years and I actually think the problem lies with the ballast or caps.

testing the capasitors on the unit can be done with a meter.

When you say that all of a sudden things went wrong. This is normally an indication of equipment failer.

If you have a schematic of the curing unit I can be of assistance.

 

[Raymond Ramirez]

hummmmm?
Questions

The enviroment of the press area? humidity/and temp

Has the technician inspected the capasitors to the lamps just because the lamps are on doesnt mean the power is smooth. and if the unit do not use caps they probably use a ballast of some sort

let me see if I can explain:

An Ultra-Violet Lamp works by vaporizing mercury within a pressurized quartz tube. In order to start, a high voltage start or spike is applied to the lamp (this is provided by the ignitor). If the voltage spike was successful at vaporizing part of the mercury, the lamp then enters its Warm Up stage.

Warm Up:
As the lamp warms up, more and more mercury vaporizes. This can take a couple of minutes. During this time, the voltage of the lamp starts off very low (around 30-40 volts), while the current that the lamp draws is high (around 20 amps). As more mercury vaporizes, the voltage slowly rises and the current falls. Once the lamp reaches around 80-100 volts, the speed of the voltage rise increases. As the lamp passes approx 250 volts, the lamp achieves ‘Ready’ status.

Ready: When running correctly in High Power, the lamp should run at a voltage of 260-320 volts, at approx 11-13 amps. This will vary slightly from lamp to lamp. In Low Power, the current will drop to around 8 amps and the voltage may drop to around 250 volts. this is based on the Olec 5k. numbers may vary depending on the circuitry and power requirements.


Common Lamp Problems:
Most problems accounted to the lamp aren’t usually the lamps fault. Most of the problems happen with the lamps power circuit, such as faulty ballasts or capacitors, or are a cause of over/ under cooling of the power supplu and/or lamphead

Cooling is very important to a lamp- insufficient cooling and the quartz will swell and breakdown. Once the quartz starts to swell, the lamps normal running voltage will drop and the efficiency of the lamp will decrease. The lamp leads may also suffer from overheating which can melt the insulation and cause a short. If the lamp is overcooled, it may take longer to reach its correct running voltage or may even be ‘blown out’ by the blower. This is when the lamp is unable to sustain an adequate voltage to remain lit. A lamp being overcooled will run at a lower voltage and so will pull a larger current. This larger current will put a strain on the other components in the system.

there are alot of things that need to be looked at. until the intrduction or CTP I had worked on Olec and Nuarcs for years and I actually think the problem lies with the ballast or caps.

testing the capasitors on the unit can be done with a meter.

When you say that all of a sudden things went wrong. This is normally an indication of equipment failer.

If you have a schematic of the curing unit I can be of assistance.

 

[Bassfishr]

Thanks Raymond, sorry it took so long to get back with you. The units we are using are the Metronic OC200, 4 color presses. here is exactly what we have and the specs are at the bottom...

Thanks Raymond i really appreciate your help with this issue. I will be talking to you very soon...

 

[cdmaster1]

Check the dyne level of the substrate, it sounds more like adhesion to me. The dyne level needs to be 45 or higher. Is the stock corona treated? Is the substrate litho grade or flexo/silkscreen grade?
Basically corona treatment is a process to burn off any plasticizer that may have migrated to the surface.
If the dyne level is to low, sometimes a primer will help, aqueous or ink.

 

[D Ink Man]

Checking the Dyne level of the stock and on top of the ink, UV cured subject would be good. Checking your lamps & reflectors for proper energy output is another step. How much wattage is being put out, and condition of the reflectors is critical. There are some sticky tabs that are available that you can place on the pre printed stock and then you collect that sheet after the curing process and see the speciality treated tab for color to give you an indication if you are curing properly. They should change to a certain color. Ask RadTech for the tab supplier, I forget. Last step would be to obtain an alternate ink with a better vehicle system designed for your specific plastic, and an ink that will have a better photoinitiator package contained in it's formulation. Hope this helps. D Ink Man