Canon Pixma G3270—an inexpensive tank-type 4-color inkjet printer

[Doug Kerr]

This is to show the battle zone I spoke of before, although now that I look at it there is a bit of a "clinker" in what I described.

This is the head parking area of my Canon G3270 printer, with the head carriage having been sent out on a prank:

Note that there are two heads on the carriage, one (the rightmost) for the black ink nozzles (in a vertical row) and a second one (the leftmost) for the three colored inks (a vertical row of nozzles, shorter than for the black ink, for each color)

We see the respective parking areas above. (Excuse the bad angle for the shot; a straight shot was not possible owing to an overhanging cover.)

To the left of each pad is a black plastic blade, these presumably used to scrape off the ends of the nozzles as part of the printer's personal hygiene regimen.

What we don't see is the "gasket walls" which I expected would be there as part of the arrangements for the pump sucking on the nozzles.

So, go figger!

Best regards,

Doug

 

[Doug Kerr]

Further observation of the behavior of my Canon G3270 printer, as well as information found in a Canon patent that seems likely to pertain to this printer family, has made me rethink the role of he "nose blowing" operation I see from time to time on my printer.

The patent speaks of the problem that small air bubbles may become entrained in the ink in the reservoir in the print head and in what I call the "anteroom", the small ink chamber immediately preceding the ink nozzles. (No, I don't know just how that occurs.)

Before I discuss the remedy for this problem described in the patent. let me review a related area. It is generally considered that in this family of printers, when it is not printing, the print head carriage is "parked" over a "capping station". The cap (which we can think of for now as a shallow rectangular "pan" containing a sponge-like pad for each set of nozzles). This prevents the vehicle of the ink in the nozzles from evaporating, which would lead to the nozzles clogging.

As part of its regular personal hygiene (as when preparing to do a print job, or just after, as well as when the user calls for a nozzle cleaning operation of one of two "potencies", ink is ejected from the nozzles onto the pads in the capping station. That ink is, so far as I know, removed from the pads by a small pump and sent to retirement in what I call the "ink sump", which in the case of this printer, thankfully, is in a user-replaceable "drawer").

Probably when the happens the cap is lowered to break its seal with the area around the nozzles. so that this process does not suck further ink from the nozzles.

Now back to the entrained air issue. Seemingly, from time to time, when the head is parked in the capping station, and the cap is tight against the are around the nozzles, the pump is started. It indeed sucks ink from the nozzles and through the pads an sends it to the ink sump. This ink carries the entrained air, which is thus removed from the reservoir and the anteroom.

In fact, it seems that the reservoir is filled with what might seem to be a sponge, whose main purpose is to prevent the ink from sloshing around in the reservoir as the head moves while printing. But in fact this sponge-like block is actually made of many plastic fibers, twisted together.

According to the patent, in this structure tiny air bubbles can propagate more easily than the ink overall. Thus when the cap comes a-suckin', the air bubbles rush to the fore, ready to be gathered up and sent into safe retirement.

I think.

Now the denouement of this story is that perhaps the periodic "nose blowing" I notice in this printer is actually an air sucking operation.

But I really don't know.

Best regards,

Doug

 

[Doug Kerr]

Another fascinating aspect of this family of printers, mentioned only glancingly in a patent, and seemingly confirmed by a remark on another forum by a seemingly-knowledgeable member, is that the print heads (which are supplied not installed, but separately, in sealed plastic packages, to be installed by the user when the printer is commissioned) are prefilled with ink.

But as I have reconstructed the ink feeding mechanics, I see why that is necessary.

If the reservoirs in the heads were initially empty, then when the ink tanks have been initially filled, and the printer does the "priming" operation (whcih is done by sucking on the nozzles by the waste ink pump), when the ink first reached the head it would drop to the bottom of the reservoir and be immediately drawn into the nozzle area. The air that intially filled the resrvoir would remain there, and the reservoir would never fill substantially with ink.

But if the reservoir were initially filled with ink (actually, I think, a little more than the desired "operating" amount), the initially small amount of air in the reservoir would be augmented by the small amount of air coming from the enpty ink supply hose during "priming", but still, when priming was finished, leaving the reservoiirs filled with the desired "operating" amount of ink.

I think.

Best regards,

Doug

 

[Doug Kerr]

This figure illustrates my understanding of the ink feed mechanics of the Canon "MegaTank" printers, and why the cartridges are prefilled with ink:

I have not reflected here the fact that (I think) the reservoir is largely filled with a sponge-like block made of plastic fibers.

On the left, items A-D show what the priming operation would be like if the heads were not prefilled with ink. Item A shows the head in schematic form, with the relevant elements labeled.

In item B, the initial priming operation has been commenced, the ink pump sucking on the nozzles (through the cap). We see that ink has been drawn from the tank through the supply hose toward, but not yet to, the head.

In Item C, the ink has reached the head. It falls to the bottom of the reservoir, and is sucked into the chamber, and out through the nozzles. We see that the reservoir cannot really fill with ink, as it is full of air, which is not removed.

In Item D, the priming task is finished, and we see the system as it would be in operation, the nozzles shooting droplets as appropriate onto the paper. But there is no enough ink in the reservoir for proper operation of the system.

On the right, in items E-H, we see the situation as I believe it actually is, with the head prefilled with ink. In item E, we see the tank in place. In item F, we see the beginning of priming, with the ink from the tank not yet having reached the head. We see that the ink level in the reservoir has dropped slightly due to the withdrawal of ink through the nozzles, but not very far.

In item G. the ink level in the reservoir has decreased a little more, but ink from the tank has reached the head, and pours into the reservoir. From now on, the ink level in the reservoir stays essentially constant, at the desired amount for operation.

In item H, we see ongoing operation, the nozzles shooting droplets as appropriate onto the paper. As ink is removed by the nozzles, new ink is drawn in from the tank. The ink level in the reservoir remains essentially constant, at the desired value for proper operation of the system.

I think.

Best regards,

Doug

 

[Doug Kerr]

I have no automatic logging scheme for determining when my Canon G3270 printer does what I describe as "blowing its nose", but I spend most of my day at the desk with the printer close by. It now seems very much that this action occurs perhaps an hour after a print job, and possibly only then.

This makes me suspect that its main purpose is to suck out ink with air bubbles entrained. Perhaps it is after such a waiting period that the bubbles gather in a way that expedites this process.

I note that there is also a rather elaborate action that occurs just at the start of a print job, seemingly more elaborate if has been a long time since the previous print jobs. I also note that there is some seemingly elaborate action that occurs very soon after the end of a print job. Part of this the action seems to be a rather "soft" mechanism operation, perhaps the waste ink pump sucking something. I think during this phase the head is not "parked", so perhaps this is the sucking of excess ink (perhaps from an earlier stage of the process) from the ink pads.

Maybe.

Best regards,

Doug