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Author Topic: Epson 7900 from the inside - out  (Read 1083035 times)

AFairley

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Re: Epson 7900 from the inside - out
« Reply #300 on: February 09, 2012, 06:04:49 pm »

+10, that tutorial is great, just to watch for fun.
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designpartners

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Re: Epson 7900 from the inside - out
« Reply #301 on: February 10, 2012, 05:45:16 pm »

that video is class! brilliant!  :)
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Eric Gulbransen

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Re: Epson 7900 from the inside - out
« Reply #302 on: February 10, 2012, 09:58:01 pm »

Can't even explain how great it is you guys like the video.  Thanks for watching it.


I wish I could update the printhead diagnosis saga but I'm struggling to break through the barrier walls of Dimatix.  I really want to talk to someone who can give me straight information on what exactly makes these things clog/fail/die.  Not what might cause these problems.  More what exactly causes these problems.  May have to resort to dressing in drag after all.  Dam lipstick..

Mark D Segal

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Re: Epson 7900 from the inside - out
« Reply #303 on: February 10, 2012, 10:08:39 pm »

Eric, failure analysis can be tricky stuff, I seem to recall from years gone by in other endeavours - what I took away from it is that failures are seldom caused by just one thing. It's usually a sequence of events, each one of which compounds on the other to produce an inevitable outcome, once you know the chain and the potential impacts, meaning one needs an understanding of the underlying science and engineering. As mere mortals, most of us aren't terribly well-positioned to get into that stuff for an Epson Stylus Pro print head, which is a pretty sophisticated piece of equipment whose functioning depends on a number of critical systems, as you've seen. In your particular case, I'm still fixated on unanswered and perhaps unanswerable questions about what happened to that printer from the time it left Dan's house until you set it up and started using it. In this case, the answer MUST lie somewhere within that chain of events, whatever they were.
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Mark D Segal (formerly MarkDS)
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Ernst Dinkla

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Re: Epson 7900 from the inside - out
« Reply #304 on: February 11, 2012, 07:05:39 am »

I wish I could update the printhead diagnosis saga but I'm struggling to break through the barrier walls of Dimatix.


Barking up the wrong tree, Dimatix knows its own products, I doubt it can tell you why an Epson 7900 head failed.

BTW, have you tried to clean the head in an ultrasonic bath or shifting the nozzle area over a vacuum tube end while feeding cleaning fluid into the head, preferably with a damper in between. The more drastic methods.


met vriendelijke groeten, Ernst
Try: http://groups.yahoo.com/group/Wide_Inkjet_Printers/


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Mark D Segal

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Re: Epson 7900 from the inside - out
« Reply #305 on: February 11, 2012, 07:13:08 am »

Ernst, are you sure after what Eric has done with the head that it can properly survive the treatment you are proposing, or is that a suggestion to experiment along the lines that perhaps he has little to lose at this stage? But do we know this? Would it not be preferable for that head to be sent to professional service people for an evaluation? Suppose the head is damaged in a manner that cleaning will not help it any longer. Isn't it worthwhile knowing whether that's the case before spending more time and effort on it? Or suppose the head isn't damaged beyond repair yet, but it needs treatment of a particular kind otherwise it could be damaged beyond repair? Shouldn't he know that too? This is expensive, delicate, precision technology to tinker around with, don't you think?
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Mark D Segal (formerly MarkDS)
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Ernst Dinkla

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Re: Epson 7900 from the inside - out
« Reply #306 on: February 11, 2012, 08:21:28 am »

Expensive it will be as soon as professional service people get their hands on any part of your printer. Vacuum is 1 bar at most, I have seen more drastic methods. The capping station pump will probably apply a similar vacuum but not on individual nozzles so it is not as effective. Ultrasonic cleaning has been used often for cleaning inkjet heads, both thermal and piŽzo. Google for it and also try to find the cases where it did not work. If you can not get that head cleaned get a new head and forget all about what may have caused the problem. You need X-ray microscopes for the best hypothesis then and with that hypothesis the head is still not open. Today I saw an ad for a water pick, too sophisticated for my teeth but with the advertised maximum 6 bar I thought it could help Eric get through the debris in the nozzle holes, with warmer water for example. If I had to spend approx. 1000 Euro on a head I would make sure that the old one is actually dead, and yes it may die in the process to resurrect it. If it still shows life in 90% of the nozzles it is not dead to me but as unusable as a dead head.

All an opinion of course. Using HP gear here and I had to exchange two heads last week, total 120 $. I might revive one for curiosity but I do not feel the urge right now, sealed it in the cup of the new one with a moistened cloth in there too.


met vriendelijke groeten, Ernst
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deanwork

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Re: Epson 7900 from the inside - out
« Reply #307 on: February 11, 2012, 12:53:11 pm »

Why would piezo heads that  should last for many years die on such a new printer? I don't get why Epson is going around replacing heads on these printers that are a year or two or less old. Our previous models could go a decade without replacing heads, and that was with everyday use. Actually the only Epson heads I ever had to replace were ones I shorted out by spraying cleaner in them trying to break clogs.  I've seen a lot of these reports of having to replace the heads prematurely in the latest series. It that really what is going on or is it the pressure leakage issues?

john
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Eric Gulbransen

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Re: Epson 7900 from the inside - out
« Reply #308 on: February 11, 2012, 12:55:14 pm »

I can't get this image of my head now.  Thanks a lot Ernst.  There I am on all fours barking up a tree at some innocent Japanese man in a white lab coat.  I just know I'm gonna wake up to that tonight..

Do you really think piezoelectric printheads from different manufacturers will vary greatly in general design?  I am not baiting you here - I am sincerely asking.  My idea in asking the very scientists who design these piezoelectric printheads themselves, is to break away from endless speculation and gather a more specific understanding of how they work, how they are cooled, what exactly their tolerances are, etc.  I can't help thinking that rather than abiding by some arbitrary rules we are told to follow, that if we all had specific knowledge about what exactly goes on in our heads, we would be better prepared/motivated to provide more appropriate care for them.  For example I see many posts about moisture, capping stations, and drying ink.  Some put jars of water in their machines and hope for the best, others monitor their rooms daily and run humidifiers.  But what exactly is the moisture doing?  Does it keep the ink from drying around the seals of the capping station only, or is it more.  Is the moisture intended to reach the printhead itself?  And if it is, it must also make it's way into the ink in the printhead itself?  I am just thinking out-loud here but what I am after is actually less random.

I would like to understand exactly what happens during the time your printer sits between prints.  For however long, doesn't matter - because theoretically whatever happens begins to happen the instant your head parks itself over the capping station, and gradually works toward clogging your head.  When I say I want to understand things like "tolerances", what I am referring to is the relationship between the size of the nozzle opening in the x900 printhead, to the viscosity (thickness) of the Epson UltraChrome HDR ink.  For instance - in monkey language, using whole numbers so I can understand this better - if the ink measures 1mm wide and the nozzle openings measure 2mm wide, then in this case we have 1mm of tolerance for our ink to get "thicker" as it is exposed to the open air through the face of the printhead, and still fit through the nozzle opening when it gets fired out during a print.  Obviously the reason we have such a thing as a capping station is to protect the face of the printhead from exposure to the "dry" open air.  And obviously, even with a capping station, the face of our heads are not completely protected from dry open air - otherwise we could leave our printers idle for a week and have no clogs to clear.

imagine for a moment, Ernst, that you are a piezoelectric printhead engineer wearing a lab coat.  You are in a tree.  I am barking the following questions at you:

So for instance just on the subject of humidifiers, which I am confident not every Epson x900 user runs in the room of their machine, what EXACTLY is going on with all this extra moisture in the air of the room that houses our printer?  Because it's not purposely affecting our printheads, per-say, but rather the ink that is inside them.  Is it a "thickness" thing?  I assume it is.  How much of a thickness thing is it?  And then how exactly does ink in the printhead react as it sits idle over time?  And how does this in turn affect the piezoelectrics?  Is a "clog" (dried ink blocking the nozzle opening) actually even a clog?  Or could it mean the ink in the printhead has simply "thickened"?  And if it has indeed thickened, what exactly goes on now?  Does this thicker ink slow down the piezoelectric movements?  Does that in turn build up resistance, which leads to overheating causing misfiring, which shows up as "clogging"?  Is "overheating" sometimes what we are actually referring to as clogs?  Is the reason we are supposed to let the printer sit after cleanings meant to allow the Piezoelectrics to cool?  Is there some tolerance to overheating then - like do cleanings clear thickened ink from the head to provide thinner ink and in turn better FUTURE cooling?  So are automatic cleanings actually then maintenance, or could they be preventive maintenance?  In the case of these uncloggable clogs then, are these indications of what we sometimes call "dead pixels" on our sensors?  Is a dead head really a dead head - an electronic failure, or is it simply a drain-o clog clearing clog failure?  Is this why our printers are set by default to regularly clean themselves - to run thickened ink out of our printheads?  Is THIS the preventive maintenance step we are all screwing ourselves out of by "saving ink" and changing our default cleanings settings?  Is it actually not clogs Espon is concerned about, but instead "thickend" ink that's been exposed too long to open air entering the face of the printhead?  

Are you scared yet Ernst?

Stepping back a moment - questions like these are what I want answers to.  Maybe the guy in a lab coat would laugh me out of a room for asking such nonsense.  But, then, maybe he would look up at me and say, "That's our biggest challenge."

Because if overheating is what causes clogs, rather than clogs being what causes overheating - and ink is what plays a key role in piezoelectric printhead cooling - then maintaining the proper tolerances of Epson UltraChrome HDR ink viscosity would soon be appointed the new sheriff in town.
« Last Edit: February 11, 2012, 01:07:45 pm by Go394 »
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iladi

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Re: Epson 7900 from the inside - out
« Reply #309 on: February 11, 2012, 03:13:04 pm »

I get clogs with dyes. In the same head as you have. Clogs are not ink thickness related. You say that a clog is dried ink in the nozzle. It may be paperdust as well. Combined with ink can easily get cement like.
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Eric Gulbransen

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Re: Epson 7900 from the inside - out
« Reply #310 on: February 11, 2012, 03:22:58 pm »

I get clogs with dyes. In the same head as you have. Clogs are not ink thickness related. You say that a clog is dried ink in the nozzle. It may be paperdust as well. Combined with ink can easily get cement like.

Just to be clear what I really am saying is I would like to avoid speculating.  At first my go-to response to gaps in the nozzle patters of this 7900 was clogs.  I understood clogs back then to mean dried up ink in the nozzles.  Now after all this open communication about clogs and printheads I understand it the problem(s) could actually be more involved than what I originally assumed. 

Thanks for your input.  Cement sounds horrible - I see enough of that crap in my day job.  And by the way it's pretty thick, so maybe clogs are thickness related?   :-)

Ernst Dinkla

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Re: Epson 7900 from the inside - out
« Reply #311 on: February 11, 2012, 03:23:21 pm »

Eric,

Check Dimatix products, there is a PDF file. Not one of their heads squirts droplets smaller than 10 picoliter. The nozzle strips are one channel mainly and often a single trip of nozzles so several are assembled next to one another to print the colors needed. If water based inks are used in them it is in the textile industry. They squirt typically solvent or UV curing inks for industrial uses, sign industry etc. Used on systems that can clean the heads in the evening etc. All kinds of piŽzohead patents exist, Epson is just one of the developers and its goal has been photo quality printing with water based inks. They are not really used in the sign industry for example just one Epson printer and some Mimaki, Mutoh, Roland models with Ecosolvent inks. When inks get really tough you will see Spectra heads, Konica heads, etc. Printers like that asks for much more maintenance and are build for that service. Rolands and Mimakis allow more maintenance by the user even when equipped with Epson heads.

Humidity at 55% is a general condition for working with papers and will not be bad for inkjet printers either. But an inkjet printer that is not in use but used often enough should have enough "humidity" within the capping station. If not, the seal of the capping station to the head is compromised by paper lint etc. and should be cleaned. When that issue often happens and users increase the humidity in the print room there will be less issues but the real problem is a bad seal in the capping station that should be cleaned. The glycols and glycerols in the ink medium function more like a retarder than the water in the ink medium does, humidity in the print room is no equivalent to their function. The waste ink pump underneath the capping station pads is a tube pump, it seals off any air getting into the pad/nozzle area if no tube or valve there is leaking. I guess in transport of your printer the capping station was not completely sealed off and possibly some ink retracted into the head. When started up again the bad condition of the wiper blade was no help either. The piŽzo pumps can not handle air in the head and any dried ink on the nozzle surface makes it worse. Imagine the situation where the piŽzo pump tries to pump air through a hole that is blocked, without a fluid there is no pumping done, no pressure build to blow out the dried ink, no fresh ink reaching the dried ink to dissolve it. The ink has not lost much of its normal consistency but does not reach into the actual pumping area.

Pigment particles are a factor of 200 or more smaller than the nozzle diameter. Already talking about microns for the nozzle diameter. The rheology of an inkjet ink is based on much more components than pigment and water and has to suit the nozzle geometry, pump activity, travel, paper coating and drying while keeping the pigment particles suspended in the carts. You can read endless documents on the web, patents, whatever and it will not help you in resolving what happened to your printer.

The advice to stop with extensive cleanings and let the printer rest for some time may be related to air bells near the nozzles that could escape in time and to give the glycols and water time to dissolve dried ink near the nozzle. I do not relate it to the electronics in the first place but it could be that the latest heads are more prone to overheating too. Blocked nozzles, air in the pump and no fresh ink around will not help then.

Based on some educated guesses, gut feelings or just my intuition.


met vriendelijke groeten, Ernst
Shareware too:
330+ paper white spectral plots:
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
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Eric Gulbransen

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Re: Epson 7900 from the inside - out
« Reply #312 on: February 11, 2012, 03:33:40 pm »

Ladies and gentlemen, that's barking up the RIGHT tree.

I feel like I should send you brownies now Ernst.

Thank you

gwhitf

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Re: Epson 7900 from the inside - out
« Reply #313 on: February 11, 2012, 06:51:23 pm »

I get clogs with dyes. In the same head as you have. Clogs are not ink thickness related. You say that a clog is dried ink in the nozzle. It may be paperdust as well. Combined with ink can easily get cement like.

This may not be related, but I had been printing many prints with Epson Cold Press Bright the week before going on vacation, and shutting down my 7900. I wonder if something related to "paper dust" from the rag paper could have contributed to my nozzle clog. I had done an entire week with Matte Black and watercolor-type papers.
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SacredEarth

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Re: Epson 7900 from the inside - out
« Reply #314 on: February 12, 2012, 01:22:05 am »

I posted earlier, and i think I got discouraged after my simple cleaning attempts, and Eric's thorough head cleaning didn't provide any positive results.  I have decided to sell my 9900 with a tough green clog as-is. I guess I just don't have the repairman stamina that Eric does and I have decided to sell it as is on eBay. (item #220952497644) if anybody wants a "fun" project or a parts printer. I'm starting it at a "low" price. ($1000.) its just over a year old and only has 300 pages on it (50 of which are nozzle checks) prints good except the green channel.....
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iladi

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Re: Epson 7900 from the inside - out
« Reply #315 on: February 12, 2012, 01:39:37 am »

Ernst +1. I think you are right.

Ultrasonoc cleaning maybe a good thing. Or not, but the head is compromised anyways. And i suggest a weekly maintenance for al 9900 users. Each friday afternoon take a few minutes and clean the whiper and the edges of the caping station. And leave some drops of cleaning fluid on the flushpad and in the caping station. For those who dare i suggest to clean arownd the head itself. NOT the bottom of the head, just the edges. Head is 90 degres rotated and is hard to see, but with a swab you can doit.
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Ernst Dinkla

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Re: Epson 7900 from the inside - out
« Reply #316 on: February 12, 2012, 04:37:20 am »


 I did read an article on clogging a while back that stated that printing with the art (rag)type papers can indeed induce more chance of fiber dust and clogs, as opposed to resin coated and glossy type papers.
 

Right, you only have to look on the surface beneath the head carriage path what dust paper lint and coating particles of art papers can create. I noticed my Z3200 had too much of it last Friday. Vacuum cleaning should be done but I have to make sure that the felt there stays flat. Self discipline for cleaning is a virtue. I think the users that have little issues must have RC papers, films, etc on their printer, that makes a lot of difference.


met vriendelijke groeten, Ernst
Shareware too:
330+ paper white spectral plots:
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
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Alan Goldhammer

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Re: Epson 7900 from the inside - out
« Reply #317 on: February 12, 2012, 09:09:48 am »

One of the advantages of sheet feed printers (3880) is that you can brush all papers to get rid of paper lint prior to printing.  I do this whether using gloss or matte paper and maybe it's a contributing factor to no clogs.
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randal21

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Re: Epson 7900 from the inside - out
« Reply #318 on: February 12, 2012, 11:11:59 am »

I have gained alot of knowledge about my newly purchased, one owner, 7900 and I thank everyones input. I sold my trusty 7800 and it truly was like the old pickup that kept starting in the morning day after day. As my friend had trouble with his 9900 he bought from someone with a known clog issue I have followed this thread to keep mine from doing the same thing and possibly facing a $2500 head repair visit. Being more paranoid I guess I have printed out a daily nozzle check status and turned on my 7900 everyday (which I never did with my 7800 and it was fine) to stay on top of a possible problem. I will also do the wiper blade exchange in the near future. I was wondering (maybe I missed it in the earlier pages) was if keeping the machine off for longer lengths of time initiates the clogging and is the humidity level a factor? It is more humid where I run my printer and think that will help keep the clogging at bay? Also, as I was reading the manual last night I ran across this on p.176 regarding after you move the printer after the initial setup:

"Keep in mind that the first time you start printing after moving the printer, the print head nozzles may be clogged _ especially if the printer hasn't been turned on for a long time. You may need to run a cleaning cycle (p 154) and realign the print head to ensure good print quality."

This struck me kinda weird as the problem seems to be with print head nozzles being clogged and don't know if it was in my 7800 manual. Just my little 2 cents worth ... but with products being rushed out the door and the consumer seems to be the testing ground (an electrician pointed out that these days alot of electrical devices go bad and they seem to use the field electricians to cull out the bad switches/plugs/etc) rather than fine tune a product until any known bugs are out (an ideal world I know)!

Thanks Eric for the video and anyone sharing their knowledge and experiences with the 7900/9900 Epsons. 
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jeverton

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Re: Epson 7900 from the inside - out
« Reply #319 on: February 12, 2012, 11:52:16 am »

I posted earlier, and i think I got discouraged after my simple cleaning attempts, and Eric's thorough head cleaning didn't provide any positive results.  I have decided to sell my 9900 with a tough green clog as-is. I guess I just don't have the repairman stamina that Eric does and I have decided to sell it as is on eBay. (item #220952497644) if anybody wants a "fun" project or a parts printer. I'm starting it at a "low" price. ($1000.) its just over a year old and only has 300 pages on it (50 of which are nozzle checks) prints good except the green channel.....

SacredEarth this is very unfortunate and I for one will not let this happen to all of us in this clogged predicament!  Itís time to get to the bottom of these recurring concernsÖ if the manufacture will not respond to this community and identify recommendations on a prescriptive or suggestive maintenance schedule, and identify alternative service providers with reasonable repair costs it only leaves one avenue worth our pursuit.

Jeff
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