Rheology

This is the simulated cartridge which is filled by a negative pressure refill, the original cartridge's wall was replace with a clear hard plastic to see the flow inside. The exit is connected to the tubing + syringe and gradully draining the ink. The native air vent mechanism is activated (with the clip !).

s you can see, the ink in the lower chamber which is the major part of the cartridge is sucked up to replace the ink in the upper chamber. The air vent system will allow the air to come in thru the right upper top of the cartridge which connected to the lower chamber (there is no connection of the air vent to the upper chamber). The 1 mm layer of ink that lay between the Right side of cartridge and the internal plastic membrane will drop the level very fast. At the point when the last drop of ink leave the lower chamber (notice some drops left over), the volume in the syringe is 7.8 ml

Then the air from chamber A that came from the vent will enter the upper chamber by the vertical duct. The air will go to the upper chamber from the bottom and bubble up to the top.

Ink in B, C and D will gradually declined and yield another 6.2 ml, incorporate with the ink from A 7.8 ml and then the total would be around 14 ml. The ink in E may get used, since the chip doesn't really read the ink level, so some of the ink left in the cartridge when the chip reads empty. For safety, Epson has made the ink stop to flow before the air can reach the circular sponge and there should be no air reach G. If some of air enter G, if it remain higher than the lower hole, it still OK. At this point, it's only < 1.5 ml left.

To better understand this, if you have the opened cartridge in your hand, it will be very helpful. 2 pictures down below will demonstrate the flow of each side again.

There is another part of this cartridge that is suspicious (about it's presence). I call this air-vent reservoir. You can see between the unused cartridge and the used one. After the cartridge used, small amount of ink will deposit into this reservoir. Where does it come from and what's the purpose of having this ?

When the cartridge was full, part of the air vent that is in the cartrige is also full with ink. So, the very first time the air vent system is activated this small amount of ink will fall by gravity into that reservoir, pass the tympanum, and will remain there forever. If the user take the cartridge out of the printer before it's used up and tilt it over. Some of the ink may enter this path and recollect in that reservoir. This also apply to the refilling. If any refill method that perfectly refill the cartridge, some more ink will deposit to this reservoir again and again

and then ?

... probably nothing much. The ink should remains in the reservoir. But after many cycles or refills, this part may be full and then it will go up to reach the front part. It then can come close the the real air path. Before it can flow backward into the air path, there is a nice wet-proof ink-air membrane that will prevent this. You can see that there is also a partial septum in the square space that separate this into 3 level.

Since the air vent path is designed to be crooked, if the tiny drop of ink get into it, it may clog the path and cause the malfunction.

May be this is the last weapon Epson uses against the perfect refilling.