wear of the printheads

[INKJET ARTIST]

If you have any chip failure printer wont print anything. Then you would not knew as well that yellow channel is OK

 

[turbguy]

The thing are not as simple as it sounds.
You have to knew that the most consumer Canon printers do have 2 - 3 nozzle rows for particular color channel. These rows are different in color intensity or in droplet size. Smaller a droplet the lighter color.

Ahhh...most Canon consumer photo printers do NOT have "different sized" nozzles for the same color. They are all the same size (Pigment Black nozzles are typically larger and fewer than color nozzles, but they are use for text/line graphics, only on plain paper). That said, some Canon inkjets might have different sized nozzles, but I'm not aware of any consumer (home) printers that do.

The real test? A service test print (with the printed grids, not pastel blocks)! If there were different sized nozzles for any color, then there would be TWO grids for any color using TWO nozzles sizes, to fully reveal any "large" or "small" nozzle issues.

Some Epson Printers appear to have nozzle check prints that exhibit this behavior (two grids per color)...

 

[INKJET ARTIST]

What is this then 3 different nozzle row for C & M. An the man is complaining that only Y canal works
https://www.printerknowledge.com/attachments/img_20171119_121458-jpg.6351/
Right?

 

[turbguy]

Good point, however that's not a service test print. Here's a sample from a six color i960 (from the service manual).

 

[turbguy]

...and from an 8 color i9900.

 

[INKJET ARTIST]

Good point, however that's not a service test print. Here's a sample from a six color i960 (from the service manual).
View attachment 8945

As you probably knew Epson has variable inkjet droplet technology: That means changing piezo impulse it can change inkjet droplet size
Canon and HP cannot do that. Canon has developed fix droplet size LSI technology. And as you can see it can be scaled up to two or three channels for the same color.
In your case you have dedicated LC and LM for better image quality. I do not knew what is particular droplet size for these channels but I do suppose it is by far bigger than the third light channel on this particular consumer print head. Something like ratio 9 vs 6 vs 3 or 8 vs 4 vs 2

 

[turbguy]

A service test print from one of those printers will be a definitive answer..

 

[Ink stained Fingers]

I could retreive a printout of a PDF file which I found some years earlier on the Epson US web site, but I cannot find it anymore, it has the title 'Epson EcoTank Printers - Powered by Epson Permanent Printhead Technology' - it is basically an advertising document claiming superiority of Epson printers. More interesting is page 6 which I scanned and attach here describing failure modes in a thermal printhead. Although it is very generic it describes two effects - deterioration of and around the film heating resistors and a clogging effect by plaque. This explains typcial observations - some clogs can be removed - cleaned away - caused by those plaques - and other defects grow and are not repairable. It is obvious from this description that the page count is not a reliable printhead usage indicator but only numbers of ink shots would be, but such numbers are not available in the firmware to my knowledge. I have seen ink shot numbers via the service mode on some Brother and large format Epson printers.

 

[INKJET ARTIST]

The main difference between Piezo and thermal printheads besides in heating and no heating is that piezo printhead is working like a mechanic pump and can suck ink out of reservoir. Thermal can not do that in most cases so therefore there is some kind of flexibil membrane near nozzles that function like membrane pump. When some ink has been thrown this volume loss crate pressure depression that that flex this membrane. And this flexible membrane now suck some more ink. But as this is very low pressure than the most of ink is delivered by gravity. And these pressure margins are very narrow.
So if you are using some third party ink fro supplier that is manufacturing universal ink, or who knows what he is selling than it can happened that you have some kind of solvent for better dye dilution and more punchy colors. And in that case in the long run with some compatible inks or cartridges this solvent could weaken this flexible membrane. But to make thing more complicate some Canon print heads are resistant to this solvent. But if they are not you can get besides Eposon explain failure, this kind of punch in this membrane

 

[Ink stained Fingers]

I'm not clear what those images actually show, but anyway, there is a collection of some older HP publications about (thermal) printhead technology, the thin film conductor/resistor, passivation thereof with some pictures including one of the mentioned failure modes - microcracks starting at p27.
https://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1985-05.pdf
This is old stuff, but the principles still apply today to thermal printheads and the reliability related to milllions of temperature cycles.

most of ink is delivered by gravity

No, look to all CISS type assemblies, the air vent channel always goes to the bottom of the ink container, and this level is below the nozzle plate level. Cartridges with foam inside don't drop, the foam is holding back the ink, and Epson cartridges have a membrane valve inside preventing ink to leak when the printhead is in idle position, all such techniques create a very slight underpressure.