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Author Topic: Epson 7900 from the inside - out  (Read 263454 times)
chaddro
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« Reply #1200 on: January 17, 2013, 10:58:17 PM »
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Eric, you posted while I was writing! But I agree with you. If 1 power cleaning won't clear the clog, you have a big problem. Maybe time to take the head out and soak it in the RED stuff, or it's equivalant!

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Eric Gulbransen
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« Reply #1201 on: January 18, 2013, 12:48:25 AM »
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Trust me chaddro by weekend's end we will know how long is too long, and why it is too long.  But first I have to find out if I can even get more RED.

As for your suction idea I appreciate that type of thinking.  Creative thinking.  So here is more food for more (creative) thought;  one channel that I recently took apart was so packed with ink that the hardened yellow ink actually kept the shape of the nozzle opening after the top of the channel had been removed.  Doubt I'm explaining this well enough to give you the picture but suffice to say sometimes our clogs are very well established.  Under a microscope, which is the only way to see this stuff, under 280x magnification you get an idea of size relationships.  If the nozzle opening has a diameter of 1, then a nozzle chamber has the width of 3, a depth of 8, and a length of maybe 40.  No matter how you slice it, or how you suck it, that's a 960lb block of ink trying to fit through a 1lb opening, with nothing to dissolve it but the same ink that formed it.  ...that's one hell of a challenge. 
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Blue moon
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« Reply #1202 on: January 18, 2013, 02:28:01 AM »
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Trust me chaddro by weekend's end we will know how long is too long, and why it is too long.  But first I have to find out if I can even get more RED.

As for your suction idea I appreciate that type of thinking.  Creative thinking.  So here is more food for more (creative) thought;  one channel that I recently took apart was so packed with ink that the hardened yellow ink actually kept the shape of the nozzle opening after the top of the channel had been removed.  Doubt I'm explaining this well enough to give you the picture but suffice to say sometimes our clogs are very well established.  Under a microscope, which is the only way to see this stuff, under 280x magnification you get an idea of size relationships.  If the nozzle opening has a diameter of 1, then a nozzle chamber has the width of 3, a depth of 8, and a length of maybe 40.  No matter how you slice it, or how you suck it, that's a 960lb block of ink trying to fit through a 1lb opening, with nothing to dissolve it but the same ink that formed it.  ...that's one hell of a challenge. 
In other words, the 1 against 960 is samson versus goliath......our mothers would have gone for the cod liver oil (guessing) and we would-be on our way to the loo in no time...son your just constipated...!
And of course from Epsons perspective the 1 droplet at a time that does get through the tiny aperture of 1 must have power behind it (960 bits of power) ...and great speed and controllability....(guessing again )
What you are allowing us to see and think about for the very first time Eric is that the flexibility of a Piezo chamber is USELESS unless it has flexible ink to play with....
Knowing you.......you probably wont be happy until you can prove that excessive power cleaning actually DOES damage piezo walls....and no doubt you will produce a photgraph of the damaged wall to prove it !!
On the other hand,possibly the hardening ink takes the rap and protects the wall behind it....you will tell us all in your own time
No tv for me this week-end
Good on you Eric
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davidh202
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« Reply #1203 on: January 18, 2013, 10:14:04 AM »
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What I have actually seen while exploring the microscopic world inside these heads is that many chambers have hardened ink lodged inside of them, but at the bottom of the chamber, so at the top ink is still passable.  While other chambers are completely clogged, floor to ceiling.  If you keep this paragraph in mind, and now recall the one that preceded it, you might now consider that power cleanings (which are the cleanings that fire the piezos - which flex the sometimes unflexable ink-locked walls) are most dangerous when we need them the most.  My bet is that a semi-clogged chamber will benefit greatly from a power cleaning, because the movement and heat will dislodge the semi-hardened ink and discharge it from the head.  My other bet is that a fully clogged chamber, with it's chamber walls locked from moving while the piezos are firing, is the chamber that is doomed to permanently fail.  I don't think there is a semi-fail, a close to fail, or an about to fail head.  I think your head is failed, or not.  

Definitely print between cleanings, like Mark says.  And definitely do no more than, quick, somebody pick a number, (1?) power cleanings before you resort to plan...  "D" - which is we don't know yet.

In my opinion you do pairs cleanings first.  If that doesn't work you try them in serviceman mode, there are four different levels.  If by then you still have your clogs, try power cleaning.  But after one power cleaning if your clog is still there, maybe you've got a problem the machine itself cannot solve.  Once those piezo's can't flex, your machine's hands are tied.  But I really think it's too early to consider it dead.  Maybe bury it, but tie a string to it's big toe with a bell on the end of it, just in case.  In the mean time, I'll be on the graveyard shift.  

I am confident ,and have said a few times now, that it is indeed excessive power cleans killing the heads.
Are you so sure that Oh'Canada blew out your head with too much pressure,or was it already burned out due to tooo many power cleans?
http://www.luminous-landscape.com/forum/index.php?topic=61585.msg585320#msg585320
David
« Last Edit: January 18, 2013, 10:17:36 AM by davidh202 » Logged
Eric Gulbransen
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« Reply #1204 on: January 18, 2013, 10:35:07 AM »
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Why do I think the clearest first thing in the morning?

Here is some food for thought, before the weekend's fun begins, on the subject of growing clogs.  It has been my experience, and the experience of quite a few others who have chimed in here, that after doing power cleanings their clogs sometimes are worse instead of better.  This has never made sense to me until now.  Now I'm not saying I know why this happens, more I am offering an idea.  Consider just two adjacent chambers - one fully clogged with dry ink on the left, the other only partially with dry ink on the right.  The right chamber still fires because ink still passes through the upper portion of the chamber, but it's in jeopardy.  The left chamber does not fire at all.  So you do a power cleaning.  This fires all chambers, all walls are charged, they all get hot, they all flex - except the wall between our two chambers because the chamber on the left is frozen stuck.  Perhaps this heat, with no movement of the chamber walls, actually bakes the already building clog in the right chamber - causing it to grow instead of shrink.

I don't know, this is just an idea.  But it could support some reason to what is otherwise, so far, a perplexing phenomenon.
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Eric Gulbransen
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« Reply #1205 on: January 18, 2013, 10:39:46 AM »
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I am confident ,and have said a few times now, that it is indeed excessive power cleans killing the heads.
Are you so sure that Oh'Canada blew out your head with too much pressure,or was it already burned out due to tooo many power cleans?
http://www.luminous-landscape.com/forum/index.php?topic=61585.msg585320#msg585320
David

That's a great question and I have a great answer.  I am sure our head was functioning before we sent it to Canada.  In fact it printed, minus the drop-outs, fine.  We only had un-clearable clogs in two colors, and those clogs were small percentages of the channels.  Our clogged channels were actually mostly clear.  There is a pic of our last nozzle pattern on page one.
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chaddro
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« Reply #1206 on: January 18, 2013, 12:40:04 PM »
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The more we talk about this, the more I can almost image what's happening in the head.

Remember, the Piezo element is in the TOP of the chamber. This was detailed in those recent posted docs (the patent one and the other, don't remember...)

When you do a power clean, perhaps all you are doing is COMPACTING he already sludgy ink, and allowing more sludgy ink into "damnation alley".

Also, there MUST BE a problem with Epson's new fancy paired capping station technology. To do something like have a solid blocked channel would take weeks and weeks of air exposure to cause this to cake up.

Now, add normal head operation, and maybe we're BAKING the ink into a toothpaste like substance until it finally hardens like concrete.

And while I'm on a roll... if this kind of clogging is gradually building up (like plaque in your arteries!), perhaps the head need to be taken out and flushed one a year to keep everything nice and shiny inside???

Or, less drastically, just fill each damper with the RED STUFF... let sit an hour (or so) and then a standard cleaning...Huh
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Alan Goldhammer
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« Reply #1207 on: January 18, 2013, 04:16:50 PM »
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I think Chaddro is correct about this assessment and the more I think about this I suspect that a head that gradually is exposed to air will cause these kinds of problems.  The capping station tolerance has to be pretty well sport on to prevent this kind of problem.  The only other possibility in my mind is poor quality control in the ink manufacturing process where there are some oversize particles that plug things up (though I don't think Epson would say this is the case).

Alan
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davidh202
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« Reply #1208 on: January 18, 2013, 04:29:35 PM »
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Why do I think the clearest first thing in the morning?

Here is some food for thought, before the weekend's fun begins, on the subject of growing clogs.  It has been my experience, and the experience of quite a few others who have chimed in here, that after doing power cleanings their clogs sometimes are worse instead of better.  This has never made sense to me until now.  Now I'm not saying I know why this happens, more I am offering an idea.  Consider just two adjacent chambers - one fully clogged with dry ink on the left, the other only partially with dry ink on the right.  The right chamber still fires because ink still passes through the upper portion of the chamber, but it's in jeopardy.  The left chamber does not fire at all.  So you do a power cleaning.  This fires all chambers, all walls are charged, they all get hot, they all flex - except the wall between our two chambers because the chamber on the left is frozen stuck.  Perhaps this heat, with no movement of the chamber walls, actually bakes the already building clog in the right chamber - causing it to grow instead of shrink.
I don't know, this is just an idea.  But it could support some reason to what is otherwise, so far, a perplexing phenomenon.

Makes a lot of  sense and very good logic  to me!!!
David
 
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Eric Gulbransen
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« Reply #1209 on: January 19, 2013, 01:09:17 AM »
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There I sat tonight, pondering more money spent, and the week or so it will take for my shipment of RED to arrive.  Until then I have only a tiny bottle to experiment with.  I sat, I thought, I finally grew impatient.  I've watched RED circulate it's way around piezo chambers enough already.  I know what happens in an hour, I know what happens in a day.  WTF am I waiting for..  I removed the un-clearable clogged head from this dead 9900 that I bought from Edward the Juggler in Colorado, for the second time in a month.  Last time I used gentle fluids, knowing full well they most likely wouldn't work.  I knew the head would be out again.  This was a learning experience.  I was fine with that.  But tonight after work I went back to page-1 of this thread, and read from top to bottom.  Funny, quite a few responses went missing, but that's not what grabbed me most.  The date of post-1 did.  Lord forgive me it's almost a year to the day. 

I knew a lot already in my first post about these machines, but at the same time I knew very little.  Man have we come a long way in a year.  But we still can't clear un-clearable X900 clogs.  Not yet anyway, which finally got my goat.  I dumped the little RED I have left into my soak tank and set ole 99 face down in the juice.  I drew RED up into each channel, particularly focusing on green - which is 98% dead.  I sealed the tank, stowed it in the cabinet, and there it will sit til tomorrow.

HAL warned me "nobody knows what it does to 900 heads.  Don't leave it long".  Well I'm gonna know what it does to 900 heads.  And soon so will you.

...you had to figure the framing hammer was coming sooner or later

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JeffW
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« Reply #1210 on: January 19, 2013, 08:29:03 AM »
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Eric,

Are we to the point of posting another thread, just to condense what would be a good guide for those looking for help. I want this thread to keep going, great stuff. Just thinking it would be great for someone looking for help to not have to weed thru all this to find some simple advice. Thanks for all the work you have done.

I think in another two or three days I will finally be back to printing after being down for FIVE months. Yes this last clog has taken me this long to clear.
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davidh202
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« Reply #1211 on: January 19, 2013, 09:38:30 AM »
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Seems to me that the only worry from leaving it too long would be softening and delamination of the adhesives bonding the layers together.
Lets hope this is not the case. ;-) 
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Eric Gulbransen
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« Reply #1212 on: January 19, 2013, 03:16:59 PM »
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You have GOT to be kidding me...

Head back in after soaking in RED all night.  Everything functions perfect.  Head is recognized, nozzle patterns razor sharp, life is good - except for green.  Still 98% MIA.

This is my theory as to why:

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Alan Goldhammer
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« Reply #1213 on: January 19, 2013, 04:59:02 PM »
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Maybe it needs some Drano™
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na goodman
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« Reply #1214 on: January 19, 2013, 06:39:06 PM »
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Eric, I have the clear. I have had it for a long time. It's in its original bottle with Japanese writing on it. Can you read Japanese?
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Eric Gulbransen
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« Reply #1215 on: January 20, 2013, 03:11:56 PM »
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My most recent focus has been finding the proper chemical to dissolve dried HDR Ultrachrome Ink.  We found that, but the deadly clogs persist.  We can only reach a small percentage of the two ends of these clogs, but the meat of the clog is untouched.  The next step in this direction is soaking longer, which I have decided against.  I am changing tack.  It's too dangerous I feel, soaking with RED too long.  The reason for this is very simple.  Each channel runs two inks.  The most delicate link in the chain which keeps these two separate inks separate, is the bond of the printhead face to the piezoboard.  Once this goes soft, green and orange won't be green and orange anymore, instead they'll both be brown.  If your head hasn't died yet in the face of cleanings, this will kill it for sure.

These piezoboards are amazingly intricate.  Even though I have a stereo microscope, and can see these boards in great detail, I have to admit they are elusive things to map your way around.  They are very difficult to light under the scope, and depending on how you light them they can and do change their shape straight before you.  This makes it very difficult to understand exactly what you are seeing.  Then there is the fact that typically they are caked with dried ink.  It's a challenge.  But recently, after the successful cleanings with RED, I have got some clearer views of these things under the scope.  Another discovery was viewing them while submerged in water.  This cleared things up even more.  

What I have confirmed now is that the line of 358 consecutive chamber walls are indeed built on one horizontal deck.  I knew this before, but what I did not know is that the deck they are built on is actually transparent.  The next thing I learned recently is that beneath these transparent chamber wall lined decks, there is a second open reservoir containing free flowing ink which runs UN-compartmentalized, for both the width and the length of the entire deck.  Stick that in your hat and consider what's next..

Upon the very closest, submerged in water under halogen lights examination I have managed to perform to date, I have discovered that at one end of each piezo chamber, at the very bottom, directly downward from the placement of the nozzle opening in the printhead face, there are incredibly tiny "steps".  Three total.  I cannot confirm what they are at this point, but I am suspect that they might actually lead to the un-compartmentalized ink reservoir below.  Why you ask do I think this, if we already know ink is supplied to the chambers by passing through the tiny space over the "speed bump"?  I have no $U*O%&)#$-ing idea, yet, but I do have an unsolved mystery to share which may be related..

*paragraph note: when I say "pressure" I am talking nearly immeasurable pressure.

When you create negative pressure at the rear of the head in order to suck fluid up through the face of the head, you get resistance.  When you apply positive pressure to the rear of the head in order to push fluid out the face of the head, you get resistance.  Nothing happens.  But after a while of soaking things do begin to move.  It does become possible to both draw fluid up through the face of the head into the chambers and out the back, and to push fluid through the chambers and out the nozzle openings in the face.  So here-in lies the mystery; how in the love of $*)%! can it become possible for both cleaning fluid, and ink mind you, to both exit and enter the chambers through the nozzle openings, if the chambers are still clogged so solid that they don't fire once back in the machine?  It can't of course, which brings us farther down this rabbit hole..

I have been sheepishly dodging my shadows for the past week about the fact that in reality I do not know how these heads work.  Not REALLY work anyway.  I mean, I have seen plenty of diagrams of piezoelectric nozzles by now.  But none of them look like what I see in these X900 heads.  So what gives?

I now think there could be two ways ink flows through the last elements of these printheads.  I also now think this is why we have the variety of cleanings that we do.  What if  ....and I realize this is a big "IF"....  these flexing chamber walls don't flex at all?  What if they're just walls?  And what if there is more to these X900 piezo nozzles than simply a hole in the roof at the end of an ink-filled hallway?  What if these "steps" are elements of an actual nozzle, supplied not by the ink in the chambers, but by the reservoir below?   The successful firing of these nozzles could in some way relate, perhaps via pressure (negative or positive), to the ink inside these chamber walls?

Stay with me for a minute here..

If a pairs cleaning "sucks" ink from the face of the printhead without firing the nozzles, it's main purpose could be simply to draw ink through the chamber passages, cleaning them instead of the actual nozzles ("steps") themselves.  It could be that power cleanings, the cleanings that actually fire the nozzles as well, are intended to clear the firing elements of the actual nozzles.  Lastly, if heat plays a role in all of this, and we know that it does because anywhere you have movement you have friction, which is heat, added to which we have piezoelectricity which is also heat - then it could be that these chamber walls play a major role in cooling as well as the passage of ink.  Let me say that this way, could it be that these chamber walls play a key role in cooling as well as the passage of ink?  Could this by why ink has such a tendency to dry up between them, because they dissipate so much heat?  ...Especially in power cleanings - which is why deadly clogs often get bigger after power cleanings?

I apologize for all the words.  I don't understand this.  I am trying to.  Definitely I got ink to both enter, and exit the printhead face via pressure from the ink supply nipples in the back of the head.  Yet the machine couldn't fire the nozzles.  I know ink is intended to pass through those chambers as part of the firing process.  How else would the ink help cooling, if it were not moving?  That passage of ink through the chambers likely plays two roles.  And ink exits our heads from two different routes.  
« Last Edit: January 20, 2013, 03:17:38 PM by Eric Gulbransen » Logged

davidh202
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« Reply #1216 on: January 20, 2013, 03:28:43 PM »
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We need to kidnap an Epson design engineer for the explaination!!   Shocked Roll Eyes

To say the least, we can appreciate why these heads are so expensive!!!
I wonder what kind of manufacturing failure rate plays into the price equation?
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Blue moon
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« Reply #1217 on: January 21, 2013, 06:15:14 AM »
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Eric
What you have now shown us is how difficult it is to clear a head that is partially clean in the first place but not in what appears to be the vital working area of the head..
And applying pressure through a syringe is not really usefull either as the liquid will flow no problem through the open reservoir area...and bypass the chamber area...
Whatever coating Epson lined the chambers with does not seem to be doing its job
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Eric Gulbransen
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« Reply #1218 on: January 21, 2013, 10:49:13 AM »
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Yes that seems to be the case - forcing fluid through the head does nothing to clear dried ink in the chambers.  And soaking them in aggressive fluids is wicked dangerous.  Not sure what step to take next yet.
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Allan Stam
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« Reply #1219 on: January 21, 2013, 10:59:00 AM »
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New person here, old clog in a 4900.  Having read through all of this several times I remain amazed at your individual and collective persistance.  Here's a question, and let me know if this is the wrong place to ask it.  With one dead channel/color (in my case VLM), might it be possible to re-plumb the head and make use of the fact that there are two blacks, photo and matte?  In my mind's eye this is really simple, just a matter of unplugging and replugging two tubes at one end of the other of them.  Surely it's more complicated if not impossible.  But for those of us that have but one bad color, is it possible to re-map the colors, then for example put a VLM cartridge into the unused black (say the Matte black if we are printing on glossy paper)? 
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