Not sure about the Mutoh smart card chips but I know on most other brand the standard chips cannot be reset. Once the printer writes empty to the chip its done. Permanently.
Aside from the smart card instead of a chip I believe the Mutoh cartridges are essentially identical to the ones used by Mimaki, Roland, etc. While the chip (including the smart card on Mutoh ones) does have a starting value and the machines write new lower values to the chip as ink is used, on a Mimaki at least, that value on the card does not actually trigger the machine to declare the cartridge empty (which the machine then writes empty to the chip). What actually causes the machine to declare it empty is the tab on the flat piece of plastic stuck to the one side of the ink bag inside. As it gets used the tab starts to stick out the side of the cartridge housing and eventually will push in a small micro switch in the cartridge slot. The ink bag is stuck to the on side of the inside of the cartridge housing, the other side of the bag has that flat piece of the plastic with the tab, as the bag empties, that tab is pulled to the side of the cartridge that the bag is stuck to. There are two ways you could cause the machine to further empty a small bit more of the bag. One would be to slightly trim some of that tab off. I'm talking a millimeter or less. The other would be to open the cartridge slot on the machine itself and slightly adjust the micro switch to be a tiny bit further away from the slot or slightly bend the metal pusher on the micro switch slightly inward so that the empty tab on the cartridge has to go a tiny bit more out before it triggers empty.
Both are risky options though. I know on a Mimaki, you can actually cut the plastic tab off it you wanted to and the cartridge will eventually go down to level 1 (almost empty) and then it will essentially keep right on printing at level 1 near indefinitely, even if the cartridge is indeed empty. The risk there is that the printer then thinks there is still ink flowing so it keep right on trying to print even though it is then dry firing the head. It will keep going on and on thinking it has ink when there is none. This is of course very bad for the head and you will be ruining a lot of material as the other colors probably still will have ink.
They have some variability built into the design specifically to prevent a cartridge from truly running dry which can cause a lot of expensive problems. Plus while it is generally very accurate cartridges can possibly have a few milliliters more or less ink. I think they are also slightly overfilled so while you bought a 220ml cartridge it might actually have 230ml in it by design. In the end, while it might seem like a lot of ink is left in a supposedly "empty" cartridge, is it really going to save you any money after the time and effort it takes to recover and use it? I actually did this about ten years ago. I bought a few new ink chips (you can find them on eBay etc), as well as a big solvent resistant syringe, and pretty large needle (real and very sharp). I snipped a very tiny bit of the needle tip to just ever so slightly blunt it some. I had a collection of dozens of "empty" cartridges. I then one by one used the needle to draw the remaining ink out of a bunch of the same color and inject it into one of the cartridges. I had enough to actually fill one full. To be sure I refilled it to the right amount I weighed a new cartridge on a scale and then refilled one to the same weight. Took the old chip off, put the new chip on the cartridge and viola - worked perfect. I just refilled a $120 (440ml in my case) OEM ink cartridge! The catch. The time and effort it took was really just not worth the trouble. Once I really stepped back and added the time up along with taking space to store all the empty cartridges, keeping up with them, buying the syringe, buying the new ink chip, them time it took to carefully empty each out and refill one..... my time is worth more than that. I realized I did not really save anything in the long run.
If you consider your personal time worthless than it might be different. In the end though, it was just not worth the time and effort to recover that 20 or 30 milliliters of leftover ink in each empty cartridge for me. Plus around that time we also switched to aftermarket inks which were less than half the cost of the OEM inks which made the savings even more minuscule....
Hope this helps and Happy New Year!
