Designjet Z6100 paper advance

**theengel** · 08-25-2017

I've got a customer who's machine is printing double images. I haven't been to the machine yet, but he says it's during the paper advance, that they seem to go bad. He also says that sometimes when he turns the machine on, and it's pulling the paper back and forth, going through it's set up routine, it will pull the paper back too far... then the print job comes, and the printer starts printing on the platen cover for an inch or so before the paper advances far enough to start catching the ink.

The paper advance system on this machine really confuses me. The last time I was there, I tried to do the OMAS calibration, but I didn't have the right paper. I tried it with the paper I did have, but it didn't work... it failed. So I would automatically assume the OMAS, but doesn't it also detect paper via a sensor in the carriage? If this were bad, then it would detect paper when there was none... right? Plus, it would fail the OMAS calibration, if it couldn't see the lines it had printed... right?

The only reason I'm obsessing over it being the carriage instead of the OMAS, is because the machine is heavily used, and everything on the carriage has a nice thick sticky coating of old ink on it.

Hopefully, someone can point me in the right direction on this... Kiran.

**Kiran Otter** · 08-26-2017

When I've seen ghosting in prints, it was usually the encoder strip and/or sensor. They come as a kit.. it's not terribly expensive and easy to replace both. If the printer is filthy I'd start with that, and the line sensor. This should rule out the carriage.

Has the printer given any errors? Use the web interface to look at the event logs and see if there's any system errors or warnings. Anything that's a 50:x would indicate an OMAS problem.

What media are they using, and what media are they telling the printer they're using? This is important because if you tell the printer it's HP Coated Paper but it's really some off the wall stuff, it already knows what paper advance to use and skips checking it with the OMAS. Basically, if it's non-HP media, then don't pick an HP media in the front panel when loading.

Have they tried it with different media?

Make sure the printer can grip the media; with the printer off, push the media all the way through the printer so you can grab it, lower the lever, and then pull on the media and see if you can get it to move. if it slides around easily, then the printer isn't gripping it sufficiently. This was a chronic problem on the 5500 using the HP Glossy media.

I keep a 36" roll of HP Coated paper with me because there's many a time where I need to do calibrations and can't because the user only has something exotic or that just doesn't work well when doing print head calibrations (usually due to coalescence.) I haven't needed to do an OMAS calibration in quite a while but I'm relatively certain you can use the HP Coated. The manual for the Z6200 says HP Coated; the Z6100 says HP Universal Instant Dry Gloss. It's the same sensor in both printers. If nothing else, tell the customer they must order a roll in order to maintain the printer.

Print the Image Quality Service Diagnostic prints (page 181.)

Run the Paper Advance Calibration, see what happens. This is different from the OMAS calibration. There's a drive roller encoder just like any other printer; if it's causing a problem it's a cheap part to replace. I'd suspect it based on you mentioning the paper gets backed up too far during initialization.

Run the Carriage Assembly test.

I don't believe the OMAS is your problem here. You can functionally disable it by putting a piece of tape over the sensor window and test. And note that the OMAS doesn't always work on all types of media. Some are too shiny or slick on the back for it to see the fibers so the printer runs without it and solely relies on the roller encoder. It can also be that the OMAS window in the platen is dirty, given the use you mentioned.

The service manual has a whole section on fixing paper advance issues starting on page 191.. including determining if the printer is even using the OMAS or not.

Last but not least, it could simply be a printhead alignment problem. I've often had people using some kind of exotic media that the printer can't successfully align the printheads on, but the user ignores it and keeps printing. I tell them to get a 36" roll of HP Coated paper JUST for alignments and tests.

Kiran

**theengel** · 08-26-2017

Originally Posted by Kiran Otter

Make sure the printer can grip the media; with the printer off, push the media all the way through the printer so you can grab it, lower the lever, and then pull on the media and see if you can get it to move. if it slides around easily, then the printer isn't gripping it sufficiently. This was a chronic problem on the 5500 using the HP Glossy media.

Kiran

You know, now that you mention it, that's a good possibility. I replaced the encoder strip and sensor on this machine a short while ago. They're using an adhesive roll, made by HP. So the paper peels off a backing once it's been printed. They're choosing the right paper in the menu.

**theengel** · 08-29-2017

This ended up being the paper slipping on the roll. I cleaned the roller as well as I could, and it seems to have taken care of it. They were also getting a double image, but it was in the carriage axis direction. I think what happened was, they were getting shotty prints because the paper was slipping. They did a printhead alignment, but that only made it worse because of the paper slipping. After cleaning the roller and realigning, everything looked perfect.

**Kiran Otter** · 08-29-2017

I'm glad it was something simple. What media were they using?

Kiran

**theengel** · 08-30-2017

They're using some adhesive roll. Like one giant label. The back wasn't just glossy, it was slick.

**Kiran Otter** · 08-30-2017

Not to put too fine a point on it.. did you catch what brand it was? Was it HP media? It would be helpful to know if you can find out.. so others know not to use it in these printers.

Kiran