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Author Topic: On ink sedimentation, agitation, clogs, and Hamlet  (Read 22872 times)

cybis

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #20 on: August 24, 2015, 02:03:43 am »

Ferp, no worries; I'm not quite sure where I'm going with this myself  ;)

Just for fun, here is a quick and dirty video of the piezo capillaries filling up with cleaning solution under a microscope: https://youtu.be/pq3OH6iFc-8
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Ernst Dinkla

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #21 on: August 24, 2015, 06:00:57 am »

Wayne, I think physics makes it unlikely that the ink bag could change shape the way you described it. After your post I tested this by pressurizing a cartridge with the cover removed and observed that indeed the ink bag inside did not change shape whatsoever.
Here is the link to the video of my test: https://youtu.be/_irPncMwIbc

Right, expected that but I have not tested it like you did and made convincingly visible, thank you. Based on several dissections of Epson carts and simple physical laws I did a brain animation yesterday of the typical Epson cart with pressure applied around the ink bladder and without. No air gets into the ink bladder without ink pressure applied so no compression of air or other gasses happens inside the bag, liquids are not compressed at that kind of pressure levels so no volume change happens, the small bulge of ink in the underside of the bladder is created by gravity and that does not change between the two stages. I can imagine PET bag material folds that readjust at some stage of the bag draining when air pressure is applied but that would be a minor stir for the ink content. I have seen some different ways of bag construction/folding/welding over the last decade and most constructions aim to make the bladder flat without interrupts when emptied, often by gluing one side partly to a vertical wall of the cart. Especially by gravity fed ink systems the bladder has to keep a constant feeding without gravity pressure changes, hence the ink outlet halfway the height and the bag flattening sideways and not dropping to the bottom of the cart.

My son yesterday gave a link to a more hilarious scientific exposé on volumes where within little agitation happens:
https://www.youtube.com/watch?v=Wf1pNnoSuQc  He intends to be there this year. If I continue writing messages like this I might end up on that stage too and it would not be a waste of time as it is comedy. Edit: even the Hamlet part of the subject line is not overlooked, drama avoided though.

Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
December 2014 update, 700+ inkjet media white spectral plots
« Last Edit: August 24, 2015, 08:22:43 am by Ernst Dinkla »
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Wayne Fox

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #22 on: August 24, 2015, 02:46:02 pm »

I guess makes some sense, most of the air pressure would fill in the empty voids and squeeze the bag as is.  I think when the bag is approaching empty it may change shape a little more as the pressure will squeeze the ink towards the port which is in the middle.

But I still believe the motion of the print head and vibration during printing is adequate to keep things suspended unless the printer sits idle for an extended period of time.
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cybis

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #23 on: August 24, 2015, 02:58:40 pm »

I guess makes some sense, most of the air pressure would fill in the empty voids and squeeze the bag as is.  I think when the bag is approaching empty it may change shape a little more as the pressure will squeeze the ink towards the port which is in the middle.

But I still believe the motion of the print head and vibration during printing is adequate to keep things suspended unless the printer sits idle for an extended period of time.

There shouldn't any air in the bag. There is nothing that would change volume under pressure. Nothing that could change shape when exposed to differential pressure. Trust me, it's not happening with the bag full or near empty or anytime. Only gravity, acceleration, vibration, agitation, and ink flow could have a mixing effect. I can't wait to put my hands on a centrifuge to see if it even matters. You are right that the printer motion may be sufficient. I think it all need to be tested.
 

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cybis

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #24 on: August 24, 2015, 04:40:58 pm »

 ;D
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cybis

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #25 on: August 24, 2015, 04:50:55 pm »

1st result : pigments settle.
2nd result: wife unsettled.
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cybis

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #26 on: August 24, 2015, 08:08:52 pm »

More preliminary results: in addition to pigment sedimentation, there is some liquid separation.

Edit: this is not a pure ink sample. Pure ink is too opaque to see the layers. This is water plus some green ink. I need to verify the same thing happens in pure ink.
« Last Edit: August 24, 2015, 08:58:04 pm by cybis »
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BrianWJH

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #27 on: August 24, 2015, 10:40:54 pm »

Here is my own experience with ink sedimentation on an older 7880 machine using Epson K3 inks, in particular the magenta inks seemed to be more prone to sedimenting-clumping, however I think the age of the inks and frequency of use are also important factors in sedimentation.

Please be aware that these images are taken with a phone camera so not real sharp, the ink damper shows extensive sediment and in the magenta ink line you can see seperation of the pigment and binding fluids.

This particular printer sat unused for about 10 months before I received it.

Brian.

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Wayne Fox

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #28 on: August 24, 2015, 11:32:53 pm »

There shouldn't any air in the bag. There is nothing that would change volume under pressure.
I know there is no air in the bag. but the printer pressurizes the space around the bag to squeeze it. since the exit is not at the bottom, some of this action will squeeze the ink upwards toward the port.

More preliminary results: in addition to pigment sedimentation, there is some liquid separation.

Edit: this is not a pure ink sample. Pure ink is too opaque to see the layers. This is water plus some green ink. I need to verify the same thing happens in pure ink.
possibly  the ink is just settling out from the extra water?
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cybis

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #29 on: August 25, 2015, 12:23:56 am »

some of this action will squeeze the ink upwards toward the port.


No, I don't think so. Imagine a flexible elastic rubber balloon filled with water and no air, tied off at the end so that water cannot escape. Suspend the balloon in a glass jar so that there is plenty of air around it. Now seal the jar and imagine there is a way to vary the pressure inside the jar. You can create a vacuum or increase the pressure at will inside the jar; the balloon will not change shape whatsoever. The liquid inside the balloon or the ink bag doesn't 'know' where the exit is since it is closed. There must be a youtube video of this somewhere; it would be a fun experiment  :D


possibly  the ink is just settling out from the extra water?

I'm also thinking that's what's going on here, especially since the volume of liquid on top seems to correspond more or less to the amount of ink I added to the water. But on the other hand that's kind of weird as pure Epson ink contains 60 - 65% water. Why would the water I added act differently from the H2O that's already in? I'm no physicist, but I'm even less of a chemist.
 
« Last Edit: August 25, 2015, 01:12:24 am by cybis »
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BrianWJH

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #30 on: August 25, 2015, 12:37:47 am »

Why would the water I added act differently from the H2O that's already in? I'm no physicist, but I'm even less of a chemist.
 
Bearing in mind that the original water would be de-ionised.

Brian.
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cybis

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #31 on: August 25, 2015, 01:05:36 am »

Bearing in mind that the original water would be de-ionised.

Thanks Brian, I used the water coming out of my RO filter. Should I use distilled water instead? Distilled, deionized, same thing?
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BrianWJH

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #32 on: August 25, 2015, 01:59:40 am »

Luc, should be the same thing, not sure if it will make a difference to the centrifuging of the mix though.

Brian.
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Ernst Dinkla

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #33 on: August 25, 2015, 03:28:29 am »

Take yellow ink straight, not diluted. Way more convincing. I have seen more pigment settling in yellow ink than in any other ink, possibly because it shows it faster, the density of the ink is low.

Met vriendelijke groet, Ernst

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December 2014 update, 700+ inkjet media white spectral plots
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Wayne Fox

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #34 on: August 25, 2015, 01:07:48 pm »

The liquid inside the balloon or the ink bag doesn't 'know' where the exit is since it is closed.
true, until the exit is no longer closed.  At some point the pressure is pusing the ink up to the port so it can get out.  If the bag is only 25% full, all of the ink will settle and expand the bag out at the bottom, possibly to the point there is little ink near the port.  As the pressure is reapplied and the exit opens some movement of ink  upwards must occur

I say this for the sake of discussion ... I agree that the changing of the bag shape is probably so minor and gradual as to not be a factor. it's probably a pretty simple gradual collapsing over time.

Why would the water I added act differently from the H2O that's already in? I'm no physicist, but I'm even less of a chemist.
 
I'm not a chemist either but guessing there is a lot more going on here than simply putting some glycol, water and other stuff in a bucket and stirring it up.  There are probably a lot of other agents used, some of which may even be for the very purpose of maintaining the suspension and mix, and just adding water and stirring it up may not achieve a similar "mix".
« Last Edit: August 25, 2015, 01:15:36 pm by Wayne Fox »
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cybis

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #35 on: August 25, 2015, 01:58:14 pm »

true, until the exit is no longer closed.  At some point the pressure is using the ink up to the port so it can get out.  If the bag is only 25% full, all of the ink will settle and expand the bag out at the bottom, possible to the point there is little ink near the port.  As the pressure is reapplied and the exit opens some movement of ink  upwards must occur.

I say this for the sake of discussion ... I agree that the changing of the bag shape is probably so minor and gradual as to not be a factor.

Yes, the bag will change shape extremely slowly as ink is being consumed (obviously) but not with the pressurization cycles at all. The port is always exposed to ink (until all the ink is exhausted), ink doesn't need to travel there as it's already there. Although as the cartridge empties, the ratio of ink flow to ink volume in the bag increases, and towards the very end of the cartridge that ratio will be high enough to effectively mix whatever is left of the ink.

I think we now agree that in the absence of ink flow, a pressurization cycle won't make the bag change shape whatsoever, correct?

Now, what happens when ink starts to flow out the bag in a pressurized cartridge? Does the bag then somehow change shape? Yes, proportionately to the ink flow to volume of ink in the bag ratio, i.e. extremely slowly. But this is unrelated to the pressurization feature. The same would happen in a unpressurized system, or even a bag less refillable type cartridge Edit: no mixing from container shape change in a bagless cartridge obviously.

 (I'm enjoying this exchange btw :) )
« Last Edit: August 25, 2015, 02:24:24 pm by cybis »
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cybis

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #36 on: August 25, 2015, 02:21:26 pm »

the ink damper shows extensive sediment and in the magenta ink line you can see seperation of the pigment and binding fluids.

Yikes!
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John Nollendorfs

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #37 on: August 25, 2015, 02:48:51 pm »

Cybis:
Remember that centifuging is different than settling from sitting. Centifuging will separate the components according to weight. But centifuging is also different than chromatography, where particle size, and not particle weight is the separating factor. But interesting things you are observing. Carry on!
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cybis

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #38 on: August 25, 2015, 03:07:10 pm »

Cybis:
Remember that centifuging is different than settling from sitting. Centifuging will separate the components according to weight. But centifuging is also different than chromatography, where particle size, and not particle weight is the separating factor. But interesting things you are observing. Carry on!

Thanks John! Yellow spinning in the machine as I type this (thanks Ernst). My understanding is that the difference between the centrifuge and gravity alone is the ratio of the acceleration force acting on component with various density (Archimedes' principle) to molecular bond forces. In both cases it's a relative density issue but gravity alone might not be able to do the work even on long time scale. So if I'm able to observe separation in the centrifuge, I'll need to compare it to a sample subjected to earth's gravity alone for a long time. 
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Damir

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Re: On ink sedimentation, agitation, clogs, and Hamlet
« Reply #39 on: August 25, 2015, 04:19:47 pm »

I'm not a chemist either but guessing there is a lot more going on here than simply putting some glycol, water and other stuff in a bucket and stirring it up.  There are probably a lot of other agents used, some of which may even be for the very purpose of maintaining the suspension and mix, and just adding water and stirring it up may not achieve a similar "mix".

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