Possible explanation for strange print patterns and other things

[Nifty]

In an effort to follow the "DON'T TOUCH" philosophy I have discovered a way to see my ink level without pulling the carts.

In the past I've used a tiny flashlight to look at the carts once the printer is open. I had a hard time seeing ink that was below the point of the clips. I realized that if I used my powerful LED flashlight I could look from above and see ink all the way to the bottom of the cartridge reservoir.

 

[Grandad35]

Another update on the "don't touch" cart test. Sorry for the length.

The second set of ("don't touch until empty") vacuum re-filled carts printed a total of 59 8x10 photos without needing a single cleaning cycle when the PM cart indicated that it was empty (With a new set of Canon carts, I only got 50 - the extra ink in the sponge chamber could be the difference). I was in the middle of a 50 sheet run, and had already printed 28 perfect sheets when the warning appeared. The PM, PC, Y and K carts were replaced - the Y and K carts had been vacuum refilled and the PM and PC carts had been "pressure refilled" (the same carts used in the first test).

The first 2 prints looked good, so I loaded the paper and printed the remaining 20. Unfortunately, the last 19.5 prints were missing PM. A total of 2.5 pages printed OK before the PM stopped - it looked like a "bad" PM cart. The carts that were just removed were then pressure refilled and put back in. The PM nozzles had some clogging from printing so many photos without ink, so I had to clean the head (using compressed air) and run numerous cleaning cycles to clear the problem. The replacement carts behaved almost exactly the same as the previous set - I got two good sheets before losing the PM again.

In frustration, I vacuum refilled all of the carts that were in the printer or that had been pressure refilled and air cleaned the head again. Now, I couldn't get any PM at all! To make a long story short, the second compressed air cleaning apparently blew out one of the little rubber seals that sits around the print heads, and there was no seal for the PM cart. I won't embarrass myself by saying how long it took to find that the seal was missing (or to find it on the garage floor), but it wasn't quick. Replacing the rubber seal restored the PM, and everything is now back to normal. The last 18 sheets printed back-to-back without a hitch on the vacuum refilled carts.

When vacuum refilling, it was noted that the PM and PC both had difficulty letting the air out of the cart. The ink chamber refill hole is plugged at this time, and the vent is also covered by a 1/2" wide piece of duct tape - the exit hole is left open. The tape is pulled down tightly on both sides, as well as being firmly pressed onto the top of the clean and dry cart to get a good seal. There was no problem with any leakage through the vent on any inks except the PM and PC. In both cases, the tape could be seen bulging up from the internal pressure in the cart before it started to leak foamed ink from under the tape. These carts refilled OK, as the tape was pushed back down into place when the vacuum was released.

The important thing to note about the vent leaks is that the exit port on the carts is wide open, so there is obviously a relatively large pressure drop required to push the foamed ink through the sponge and filter. There are several points that are of interest in this regard:
1. It has been reported by others that PM and PC commonly give the most problems with refilling and give the fewest number of refills before a cart goes "bad".
2. Some people call it "foamed ink" and others call it "air in the sponge", but these two are probably the same phenomenon viewed through different eyes. Another way of looking at it is that foamed ink consists of ink bubbles with air in the center of the bubble.
3. When air or ink foam enters the sponge, it apparently forms a block that makes it difficult for further ink transfer through that area.
4. If the ink chamber is allowed to empty, just such an "air barrier" may form on the back of the bottom sponge.
5. Not all inks seem to develop the same resistance to flow when air is in the sponge, so not all inks may suffer to the same degree from this problem .
6. This problem is almost certainly affected by the individual ink formulations of the various ink suppliers. It is anticipated that the "air blockage" will be a bigger problem with some inks than with others.
7. This is not a problem unless you refill.
8. If you only print a little at a time, it is probable that this problem will be greatly reduced or non-existent since the replacement ink has a much longer time to migrate through the sponge.

Conclusions:
1. Be very careful when using compressed air to clean the head. Those little black seals are important and can be blown out. I used 20 psi for the first cleaning and 30 psi for the second cleaning.
2. The "Don't touch until it is empty" approach looks good if you are using new or vacuum refilled carts, but it caused problems with conventional refilling (at least on the PM cart).
3. The approach of refilling the cart while it still is about 1/3 full makes a lot of sense in light of this experience, as it should minimize the possibility of getting air into the sponge. A good combination might be to combine this with Nifty-stuff's idea of using his flashlight to allow you to see the ink levels without pulling the carts to give a "Don't touch until it is only 1/3 full" approach. Is it possible to refill a cart in place to eliminate the need to pull the cart at all?
4. If the "Wired Beans" carts have a sponge that doesn't have the same flow restriction, they could be a good solution.
5. Vacuum refilling can rejuvenate a "bad" cart.

 

[Nifty]

Grandad, I think I'm voicing the opinions of many when I say you're posts are never too long. Personally I really enjoy reading them.

I'm glad you posted your results with the compressed air. I'm personally reluctant to use this method as one of my early attempts at cleaning plugged nozzles. As I've stated elsewhere, after cleaning cycles I usually go to rinsing the head under the tap until all the water runs clear (I use to use distilled, but moved to tap). I rarely have to progress past this point as this usually works.

I'd never refill carts while they are in the printer. It's a bit too tight for movement but with plenty of room for error and a mess. I know some people do this without issue, but I know how much ink comes out of my cartridges when the plug is removed, and also what a bad seal on a cartridge can do to the printer and other cartridges and I'll avoid that at almost any cost.

I agree, "topping off" cartridges seems like the best way to go for a variety of reasons.