Designjet Z6100 banding

[Kiran Otter]

Yes, the HP's do it too. On the Z6x00 you can 'force drop detection' which resets the nozzle health database and starts a new drop detection.

I know other models do it as well but the option to reset the data is not available.

Kiran

[theengel]

This thing is driving me nuts.

If you look in the video, about halfway through the big blocks of color, you can see these solid white lines. Those come out as light bands in the end. Kiran mentioned the two lines of printheads, and I thought maybe it was normal and had something to do with that. But that's not the case. I watched another Z6100 do a test page, and it doesn't do that at all.

On "tech support's" suggestion, I replaced the carriage unit & carriage board. I didn't have much hope in that, and I was right, it did nothing for me. Still banding. I went through most of the manual's suggestions on banding, and it just doesn't seem like it's helping. When I run the paper advance visual test print, it looks almost normal. There was one line that looked weird, but I think I had tugged on the paper for that one. Everything else looks like it should.

Grrr.

[theengel]

The type of paper they're using is HP Polypropylene Matte.

The manual mentioned types that won't work with the OMAR, and this might be one of them, but I'm not sure where to find out, and how to 'disable OMAR' in the test prints. Also, it said to look for OMAR flashing red, but I'm not sure where I should see this going on. When I run the OMAR Calibration, everything appears to go well, and then at the finish, the machine says "Calibrating PixelSize Offset" and is stuck on that until I turn the machine off. Could I just need a new OMAR?

[Kiran Otter]

Something I want to note: Always.. always.. try replacing the consumables first before replacing something like a carriage assembly. I know you said you replaced some of the printheads, but I would look at the usage of the others and replace any with either a lot of hours on them, or a lot of ink through them. How much is a lot? 800ml seems to be a lot for these printers, but I've seen heads with 1200-1500ml that were still reasonably functional.

I can't see the actual nozzle pattern in the pictures but let's assume they all look decent.

Judging by the way the carriage puts down the ink bands.. I'm not sure that's definitive. Depending on the type of media selected, the printer will lay down ink in various ways to achieve the best coverage. Try telling the printer this media is HP HW Coated, or even just Plain Paper, and see if anything changes.

Anything from HP that's 'matt' media should be compatible. It would be important though to try other media. I also recommend users keep a roll of 24 or 36" HP HW Coated paper purely for testing and doing print head alignments on. It's cheap and you're not wasting their vinyl or canvas, etc. If the printer prints correctly on the heavy-weight coated paper, then you can rule out printheads, usually.

The OMAS (not OMAR is a tiny window in the platen. It's near the 6th platen roller from the right.

2016-05-11_1233 - Kiran_Otter's library

The manual says it's OK to use alcohol to clean it.

If you've fiddled with the calibration settings, I would (and have) always gone into the Paper advance calibration and reset the paper advance. Start from square one and rule out the media and printheads on HW coated paper.

Kiran

[Kiran Otter]

By the way, if you have access to another Z6x00, borrow the print heads from it and try them in this machine. And vice versa if you want to be really thorough.

[theengel]

Thanks.

I tried telling the machine I was using another media, and it did the same thing. They use this media for just about everything, and have used it for a long time. They use it on 2 different Z6100's. The printing of the same test pattern on the same media looks completely different on the two printers--there's not that white band that appears during the printing on the other Z6100. I haven't tried changing the media type to plain paper yet--I might try that, and if it works, look into the media profile updates.

Ha Ha--OMAS, not OMAR. I cleaned it with a damp cloth, and it looks pretty darn clean. Maybe I'll try some alcohol.

I've replaced all of the printheads at this point, but I might try swapping them with the machine next to it. The nozzle patterns look pretty good.

I reset the paper advance, then ran the paper advance calibration, then fiddled with it, then reset it, etc.,.

[Kiran Otter]

OK. I spoke to HP about this because I wanted to know what's going on, and this is apparently very common.

It's due to a dirty or contaminated drop detect sensor. The printer thinks way more nozzles are bad than really are, and is trying (desperately) to compensate for the bad nozzles with working nozzles. You need to clean the drop detect sensor (damp q-tip or just a folded up paper towel, damp.. cram it in there and work it around.)

Then go into the service utilities menu, diagnostic print, others, and select forced drop detect. The display will show how many nozzles are missing for each printhead. You can compare these numbers to what the image quality print is showing. Obviously if it says there's 100 nozzles out but you only see one or two missing in the print, this is your problem.

If cleaning the drop detect doesn't do it, I would just replace it.

I'm sorry I didn't think of this sooner.. I sort of always clean the drop detect as part of my PM I do anytime I work on a printer so it didn't occur to me it might be the problem.

Kiran

[theengel]

Sadly, I lost this job. This was third or fourth party work, and someone in the chain (possibly the end user) wanted a new guy... I've put too many hours into it without results. Oh well... it's nice to finally know the answer though. Thanks.

[Kiran Otter]

Well that, as they say, sucks.