CET Flatbed gloss banding issues

[Tom Dalton]

Has anyone with a CET Flatbed ever experienced gloss banding issues? If so, what was your fix or did you just switch to printing at slower higher pass print mode? Talking about results like this... (see solid filled dark blue in attached image). That area isn't suppose to have large stripes. It is bands of glossiness. I think getting the LED UV option might have been a mistake. I also think we're about out of options and the final answer will be "print slower". We have 6-color gen-5 and the whole thing has about 6 weeks of use.

 

[ChrisN]

Is that one pass printing? I think what you're seeing might be a combination of chromatic banding (aka lawnmower banding) and gloss banding. The fix for chromatic banding, is printing with more passes, which comes out to slower printing. As far as gloss banding, I discovered with my Agfa, that running the lamps trailing only makes for a much more uniform gloss as opposed to running leading & trailing. I don't have a CET flatbed (yet), but I'm sure you can do that on your machine.

 

[Nicky Zhou]

That glossy banding is very common on most of the UV printers, That glossy banding was generate due to the ink not cured in the same degree, you can find some white paper on Dimatix website, there is a detail explanation.

So far I only see that Durst printer solved that issues with low pass printing. For others, it is still.

To reduce that banding, you can print with unidirection, increase the passes? If you have better ink, it helps, as well as the UV system.

 

[Tom Dalton]

Is that one pass printing?

Far from it. 4 or 5 pass. One thing you can't tell from the pic is that the bands are about 4" wide.

I discovered with my Agfa, that running the lamps trailing only makes for a much more uniform gloss as opposed to running leading & trailing.

Great tip. I'll see if that is possible with the CET.

Thanks

 

[Tom Dalton]

If you have better ink, it helps, as well as the UV system.

Is there acceptable 3rd party ink for the CET that are better than the CET inks? I guess any ink that works with the Ricoh Gen5 heads would be acceptable ...but likely not supported. For the UV system we went with the LED upgrade. I still think the LED option was too bleeding edge of a choice at this time.

 

[Nicky Zhou]

Is there acceptable 3rd party ink for the CET that are better than the CET inks? I guess any ink that works with the Ricoh Gen5 heads would be acceptable ...but likely not supported. For the UV system we went with the LED upgrade. I still think the LED option was too bleeding edge of a choice at this time.

Hi Tom.

I am sure if you can use the 3rd party ink on the CET printer, the Ricoh head need a special waveform for different ink, if CET open that function for you, then you properly can use a third party ink.

Right now, the ink work on Ricoh including: Agfa(The most popular in China), Sunjet(only some).. I know that Hantop/CET have been test the Agfa ink as well, during printing at 4pass, it still have banding, then could not be your choice.

Why not test a configuration at KCMYYMCK? that head installation, can decrease that banding..

The LED curing system, it seems weak, maybe due to the ink properties. But I am not sure. The fact is even I checked that printer with mercury lamps, banding still there at low pass.

 

[Tom Dalton]

We started with 8 head CMYKx2. Now, to help with gloss banding, we switched to 6 head CMYK+LightC+LightM.

 

[ChrisN]

Far from it. 4 or 5 pass. One thing you can't tell from the pic is that the bands are about 4" wide.

Great tip. I'll see if that is possible with the CET.

Thanks

So are the bands of gloss larger than the step size? For example, 4-pass on my Agfa gives a different sheen every 1/4", the same as the step size.

 

[Nicky Zhou]

We started with 8 head CMYKx2. Now, to help with gloss banding, we switched to 6 head CMYK+LightC+LightM.

Oh, Really, do you mean when you switch to 6 heads, the banding decreased or just ink density decreased?

 

[Tom Dalton]

So are the bands of gloss larger than the step size? For example, 4-pass on my Agfa gives a different sheen every 1/4", the same as the step size.

No. but it is probably a multiplier of step size. Like, Step size x number of passes.

-Tom

 

[Andy D]

Those are UV lamp banding, It typically happens when
one or both of your lamps are set too high.
You see it more the darker the color, right?

 

[In Print]

We have the CET on the Gen 5 with UV lamps and its basiclly a known fact. on a dark solid patch on any screen over .33x you will get that.

 

[BIG EASY DOES IT]

Lower passes is not usually better, actually hardly any of the time. Stop trying to make the cheapest item possible and charge accordingly for the quality product you make. I mean charge for the time, and added lamp time, and ink that comes with extra passes and make that your standard. Or keep racing to the bottom.

 

[TXFB.INS]

to ensure transparency, has CET been contacted? if so what was their suggestions?

I know there have been several threads about their machines and they have seemed to be on top of threads related to them

 

[Tom Dalton]

Those are UV lamp banding, It typically happens when one or both of your lamps are set too high. You see it more the darker the color, right?

Yes. More on darker colors.

We got the more expensive LED UV option. While LED has its benefits, one benefit is NOT this it has a bunch of options for UV intensity. In fact, there are zero options for UV intensity.

-Tom

 

[artbot]

when i was being trained on the old CET, Ice explained it to me this way. the dot of ink impacts the substrate, sticks and then slightly bounces the carraige direction, stretching the ink in that direction and then is instantly cured in this stretched position. on a microscopic level, think of it as rows of footballs leaning all to one side then to the other side, like scales, i guess. these scales have a reflection angle going one way that is different than the other way. there's some term for interweaving the dots (which slows the prints down)... it was in the firmware menu. don't remember that term.

 

[uvgerard]

Gloss banding and LED UV lamps

I come from the conventional arc-lamp end of the UV systems business so my comments are somewhat skewed. There is propaganda regarding the features and benefits of LED UV curing systems. If you listen to some salesman you would think LED-UV systems cure everything, cost little and perform better than conventional UV systems. If you had a conventional arc-lamp system your solution to reduce gloss banding and might be as simple as increasing UV lamp power or replacing both lamps at the same time (this maintains equal UV dosage when printing bi-directionally). Such a fix is economically impossible with a UV-LED system. All our CET lamps are priced under $210.00

LED-UV systems have little radiated “heat”. If you’re looking to increase adhesion heat is a welcome ally. Too much can be an issue but is relatively easy to deal with. If your problem is ink related there is a limited availability of special LED-UV inks. You can find far more companies offering conventional UV inks that will be able to cure over the UV spectrum (280 to 450 nanometer) afforded by conventional UV arc lamps.

I trust CET will work with you to solve your problem

 

[greysquirrel]

Linearize your profiles to minimize ink levels...printing uni directional will make it look more uniform...but on certain medias with certain colors, dark blues, grey, purples you willl see more cure banding. Running at higher pass mode (yes slower) will minimize this affect.

 

[Tom Dalton]

When I started this thread 3 years ago, we had a CET that ran Ricoh gen-5 heads. Now we have the newer one that uses the Kyocera print heads. It has the same gloss banding issue though. Any more info on mitigating this issue would be helpful. our only solution is to print unidirectional (slow). Artbot, did you ever think of the term for interweaving the dots?

 

[Bly]

Have you tried different levels of UV lamp?
Sometimes we can reduce this by turning off the trailing lamp on our Arizona.