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Aeg Print
10-11-2021, 01:04 PM
Hello all
i have a very strange problem in a C7000 after a client call for uneven color in Magenta we changed the dev Unit all 4 drums, 4 coronas 4 developers but the problem was exactly the same (2 lower density strips in the length of the paper towards the back side of the machine)
the test prints was in DOT 1 profile. when we tried DOT2 the machine prints perfectly. Also all the test prints from inside the machine (except #53) print perfectly as well. this happens to all paper sizes we tried with the unevenness in the same place.
The machine has 1,1 mill. clicks and it is in a very good state overall.
50371
Any ideas or suggestions will be appreciated.
i am attaching a scan of the problem in the print.

Aeg Print
10-12-2021, 10:26 AM
Update. a tech friend of mine suggested that maybe the laser unit is the problem. because it happens only at magenta and everything else is changed.
Any opinions welcome

raplma
10-12-2021, 05:15 PM
Having got a c7000 with 12M clicks on the clock, we've not come across this type of screen artefacts before.

One thought did come to mind - and it is stating the obvious - I'm assuming that after you have changed the screen type on the c7000, you are then running the usual image adjustment processes on the machine and then once complete doing the usual calibration through Command Workstation? There are some jobs for which we change the screen type, and you'll get two very different outputs if after changing the screen type on the machine you've not then run the usual image adjustments and calibration proceedures. We always run the adjustments and calibration after a screen change.

The only other thought is there are known cases in the earlier machines where a certain combination of settings causes a build up of dev/tonor on the mag roller of the dev unit, to the extent that the drum touches this bulge transfering it onto the ITB, but this is usually K rather than CMY.

Couple of random suggestions, run the job greyscale and see if you still get the magenta plattering, that would suggest dev/dev unit rather than lazer. Change the stock you are running, not just another of the same weight, but also heavier and lighter, and change the settings to match the stock.

Is there a reason why you can't run the job Dot2 anyway seeing it gives the output you require?

Some random thoughts
Good luck and keep us posted.
Mark

Aeg Print
10-12-2021, 05:57 PM
Having got a c7000 with 12M clicks on the clock, we've not come across this type of screen artefacts before.

One thought did come to mind - and it is stating the obvious - I'm assuming that after you have changed the screen type on the c7000, you are then running the usual image adjustment processes on the machine and then once complete doing the usual calibration through Command Workstation? There are some jobs for which we change the screen type, and you'll get two very different outputs if after changing the screen type on the machine you've not then run the usual image adjustments and calibration proceedures. We always run the adjustments and calibration after a screen change.

The only other thought is there are known cases in the earlier machines where a certain combination of settings causes a build up of dev/tonor on the mag roller of the dev unit, to the extent that the drum touches this bulge transfering it onto the ITB, but this is usually K rather than CMY.

Couple of random suggestions, run the job greyscale and see if you still get the magenta plattering, that would suggest dev/dev unit rather than lazer. Change the stock you are running, not just another of the same weight, but also heavier and lighter, and change the settings to match the stock.

Is there a reason why you can't run the job Dot2 anyway seeing it gives the output you require?

Some random thoughts
Good luck and keep us posted.
Mark

Thank you your reply.
The Drum, Corona, and Dev unit are brand new. this happens only in magenta. all other colors print perfectly. (we tested with several files in a wide range of papers from 120 - to 300 gsm with exactly the same output)
When we use dot 2 (also calibrated after the Dev Change) the magenta prints flawlessly. the color is even without any visible problem. The thing with dot 2 is that the machine prints with bigger dots and we have issues in small letters and very rough gradients. (the clients prints labels with very small fonts)
It is worth mentioning that when we test print 80% and above solid magenta it prints perfect and in DOT1
I really don't where else to look.
Your help is appreciated.

raplma
10-12-2021, 08:34 PM
Indeed can see why you need dot1.

Apologies for labouring the point, but you mentioned calibration after Dev change, but did you do the relevant process adjustment and cws calibration after each time you changed the screen type?

What happens when you run the job greyscale?

The only other idea that comes to mind although highly unlikely is if the Moir effect is playing some strange effect, what happens when you run the job 90 degrees rotation? Also try 180 degree rotation, I know it sounds weird but halftone greys always play hard to get on th c7000 and these are some of the tricks that work. I have even run single sided jobs duplex with side 1 being blank so the image prints on the second pass. Don't ask me why but it has made a difference on the odd awkward job.

As you can tell I'm not engineer, just a printer whose got a few years of shouting at the machine!

Toxic
10-12-2021, 10:48 PM
Maybe try this procedure, its from C6501 series but principle is the same
50377

Aeg Print
10-13-2021, 08:35 AM
I have to re mention some things. The Drum is brand new (in fact i replaced all 4 of them) the dev unit is brand new, the belt and the belt cylinders are new, the problem occurs only in magenta so if i print the same file in B/W it prints flawlessly.
in dot 2 magenta prints perfectly in any file and any paper.
The next step for me is to switch lasers to see if the problem re occurs of if it changed color but i really dont want to mess with the lasers too much.

Does anybody know if it is possible to recalibrate the laser or reset it somehow before i make the switch?

feracampos
02-13-2022, 04:03 AM
I am having the same issue. Any thoughs?
Thank you.

ANIP87
02-14-2022, 07:58 AM
Hello all
i have a very strange problem in a C7000 after a client call for uneven color in Magenta we changed the dev Unit all 4 drums, 4 coronas 4 developers but the problem was exactly the same (2 lower density strips in the length of the paper towards the back side of the machine)
the test prints was in DOT 1 profile. when we tried DOT2 the machine prints perfectly. Also all the test prints from inside the machine (except #53) print perfectly as well. this happens to all paper sizes we tried with the unevenness in the same place.
The machine has 1,1 mill. clicks and it is in a very good state overall.
50371
Any ideas or suggestions will be appreciated.
i am attaching a scan of the problem in the print.

You can try to print gamma offset adj for DOT 1.

Aeg Print
02-14-2022, 10:49 AM
You can try to print gamma offset adj for DOT 1.

already tried all calibrations (offset adj etc.)nothing works the problem is exactly the same.
does anyone know how can i enable the line 1 screen in fiery in order to try printing in this also?
it is disabled in the printer driver and i cannot select it.

Synthohol
02-14-2022, 01:25 PM
use command workstation to adjust dot 1/2 by default.

feracampos
06-27-2022, 09:31 PM
I've had a similar problem with our km c7000. I was solved on about 90% replacing the developer.
After a few months, I replaced the Developer Unit and the problem was totally solved.

I'm using the C8000 toner and developer, when replacing the developer I'm using only 120grams, because the c8000 refill has about 150g.
Where working with that configuration for about 3 years, flawless.

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