Designjet 4000 printing random black lines

[theengel]

The lines start off randomly and it looks like a single nozzle. But after the customer prints for a while, the lines get more consistent, and then thicker, as shown in the first image. The next two images are diagnostic prints. The fourth is a nozzle check which doesn't seem to reveal anything at all.

I assume I should start with replacing the black printheads, but is there something I'm missing?

Thanks,
Scan1.JPGScan10001.JPGScan10003.JPGScan10002.JPG

[Kiran Otter]

Re: Designjet 4000 printing random black lines

I usually see this due to cross-talk among printheads; you may actually have a bad yellow printhead that's causing the black to miss fire.

I would remove ALL of the print heads, clean the contacts (just use water, never use alcohol) on the back of the printhead and in the carriage, and try it again. If it continues, try swapping heads 1 & 2, and see if the pattern changes. Then 3 & 4, and so on. If the behavior changes, I'd suspect one or both of the heads you moved around.

It can also be a bad carriage PCA.. but of course rule out the consumables first.

Kiran

[Lotar]

Re: Designjet 4000 printing random black lines

Print heads

[theengel]

Re: Designjet 4000 printing random black lines

I usually see this due to cross-talk among printheads;

...

It can also be a bad carriage PCA.. but of course rule out the consumables first.

Kiran

So could it also be the flex cables themselves?

[Kiran Otter]

Re: Designjet 4000 printing random black lines

It could be, if they've been damaged or mangled by someone trying to clean them. I had one user using nail polish remover to clean them.. made them curl up like potato chips. But if the printer is printing and not complaining about bad print heads, I would say the connection between carriage and print head is OK. I would clean them and then try swapping heads to see if you have a bad one causing another to fail.

If you have access to another 4000/4500, borrow the print heads just as a test. If they do the same thing, I'd say it's the carriage PCA.

Kiran