Learning how to dial in volts/temps to eliminate banding

[MrNick86]

I have been running this CET FK512X for a year now. I still cannot seem to smooth out my banding. So, I have provided photos of each color with the fastest print speed so you can see the density difference between bands.

As you can see from the photos, The first half of the second pass of every color is darker, which shows up as banding after its complete pass. I have been tackling this for months and have got nowhere. It is frustrating to have to slow down my print speed when printing large areas of darker colors, or colors that use all CMYK like grays, tans, and blacks to avoid the uneven coverage.

 

[Gino]

I could be reaching a little far on this, but just about ANY printer.... be it flatbed, roll to roll or whatever always bands at it's highest speed. High speed mode is for like real estate banners going about 50' in the air..... much like billboards. Have you ever seen their pixilation ?? It's stoopidly ridiculous.

 

[MrNick86]

Yes, I have seen this. But I was more so getting at using the highest print speed to see the width of the band better. There should be a way to balance out the coverage of the passes.

 

[Gino]

When we got our very first wide format about 15 years ago, we were told of the fastness... at high speed, but to be careful when using it as it's really not prone to being used for normal signs of any sorts.

Once you dial in and get the banding to stop, you'll have slowed it down, made more passes and done all kinds of other things to eliminate the banding, that you will be closer than you realize to a production mode.

So, why not just use a normal sign mode profile ?? Besides, the colors are so washed out in fast mode.

 

[MrNick86]

I have to learned how to compensate the "washed out color" from printing fast speeds like 360x1080. I usually add in 10% ink through the rip to make up for that. I like to take advantage of the print speed when I have 30 hours of printing on some jobs. Printing faster on jobs that have heat sensitive substrates helps as well.

What is the average print speed everyone runs on here? I hear 720x720 quite often, I say I usually get the best results on that setting, even no extract.

 

[artbot]

720 x 720 bidirectional slow carriage cmyk (no lm lc) no extractions (CET terminology?) for us is the best balance of print quality and speed.

 

[Gino]

If you're just going for speed alone and not worrying about the longevity of your prints, let alone the proper adhesion by using proper profiles, then just do what you're doing if you can't afford the right machine with built in speed and jeopardize your customer/vendor relationships. Remember, laying down ink using wrong profiles and quick cutting of corners is gonna come back to bite you in the butt, when they fail far too long for what you are telling them they will last. While it takes years to build a good reputation.... it only takes a day or one person to ruin that long hard road to success.

Keep looking for that quick fix and ignoring what your techs have told you..... and you're gonna be running a lawn mower, instead of a printer before too long.
​

 

[MrNick86]

#Gino
I am all about quality, we all are at my shop. but we do know the potential of this printer and we have seen it. There are combinations of problems that are causing quality issues where resorting to slower print speeds is the only way to put out a quality product. These issues are being addressed. it is only a matter of time before we will get our machine running at its top performance again.

 

[omgsideburns]

What do you mean "the first half of the second pass" is darker? Like.. could you post a picture and highlight it?

 

[10sacer]

Banding

What is your room temperature and humidity?

I have been running this CET FK512X for a year now. I still cannot seem to smooth out my banding. So, I have provided photos of each color with the fastest print speed so you can see the density difference between bands.

As you can see from the photos, The first half of the second pass of every color is darker, which shows up as banding after its complete pass. I have been tackling this for months and have got nowhere. It is frustrating to have to slow down my print speed when printing large areas of darker colors, or colors that use all CMYK like grays, tans, and blacks to avoid the uneven coverage.

 

[ironchef]

My room temp is at 70-73 and humidity is at 16% .... I know thats pretty dry, but i havent noticed an issue except the static zaps i get once in a while

 

[10sacer]

I think thats what you are seeing is static affecting the nozzle spray laydown. 16% is way too low to be used in flatbed printing. I am in North Carolina and run at 55% all day and have no issue.

My room temp is at 70-73 and humidity is at 16% .... I know thats pretty dry, but i havent noticed an issue except the static zaps i get once in a while

 

[ironchef]

I dont have a flatbed, but i agree i need to bring up the humidity

 

[Gino]

I dont have a flatbed, but i agree i need to bring up the humidity

Yeah, if for nothing more than to stop those nosebleeds............

 

[artbot]

this is a long shot. during printing, does it seem that one flap on your lamps opens wider/more aggressively than the other. you mentioned that it seems like alternating passes are of different densities. could this be some form of cure banding in which you've got more dot gain going one way than the other due to a different amount of jules going left vs right. i'd assume there is some sort of isolation test that could be contrived. first i see on a small test print of some kind if you can repeat the exact pattern of light/dark/light. now flip you lamp to fore vs aft. check that next sample. now lay the uv down all lamps blazing both directions. look at that test print. do these last prints appear to be better or different than your control?

 

[MrNick86]

I did one test with trailing lamps on Unidirectional and unplugged the second row magenta head and printed 100% magenta. I noticed that some passes were more or less dense than the others. I unplugged the opposite head and printed with similar results.

Is that enough to make you scratch your head?

 

[artbot]

i'm so brain dead i can hardly decipher my own theory right now. (did an all nighter, still going). there'd have to also be a way to take into account that the ink is cured in a passive way intermittently between threads by the other lamp. or is the ink cured in one single pass of the uv. i don't think it is completely cured in a single pass.

 

[MrNick86]

No, but the light does pass over multiple times. Especially with multiple extracts.

 

[artbot]

my consideration was with cure banding, there is a thread that has more dot gain than another. thus the color is different accounting for the lack of negative space between the dots. the first pass may not cure the ink completely. but i'm assuming with the first pass, it ends any possibility of further dot gain.