Canon CLI-8 Sponged Carts. Understanding Their Operation & Properties

[canonfodder]

WARNING: This may be an FNO Post.

The Canon Sponged carts are really very special. They represent an invention that may be simple in its manufacture, but it embodies very shrewd engineering and probably is the best inkjet ink cartridge that has been made.

Over the past few months I have become extremely familiar with the Canon sponged carts. The patents must be protecting Canon's position pretty well, because there are no successful imitators that I have seen. When I speak of imitators, I do not mean "near imitators" or "almost imitators". A true imitator would be someone selling carts that have the same construction and the same performance as the Canon sponged carts, with no functions left out.

Some alternative cart makers brag about the absence of sponges in their carts. I can understand what they are talking about, because extending the life of a sponged cart is hampered due to a build up of some contaminant in the sponge which eventually blocks ink flow. This blocking of ink flow is very correctable by using Grandad35's Purging Process, see: http://www.nifty-stuff.com/contact.php , but it would be quite desirable to eliminate that need by eliminating the sponge. However, NO SPONGE = NO GREAT OPERATION. Others may get SOME functions to work well in their spongeless carts, but there will be important capabilities left out and there will often be erratic operation. You don't have to go far to find someone with a tale of woe concerning alternative carts used in place of Canon OEM sponged carts.

I would not dare say that an equivalent performance cart can not be made by using some other technique than the sponges. Inventions never end. Improvements never end, no matter what type of hardware or software you are speaking of. In 1943, I told my father that, "Airplanes built with four engines would be too heavy to fly and carry great loads". That was my last prediction or proclamation of physical limitations placed on inventions. Dad just opened a Life Magazine and showed me a new military airplane that could carry a great load of bombs or such, and it had 4 engines. I was younger then.

I am going to stop here, because I always put too much in my posts. If anyone would like to know something more about the Canon sponged carts and what makes them tick, and what makes them special, I will answer questions, even if I have to get help to do that.

Right now, I have a question of my own.

Does anyone know the ink pressure right at the interface between a sponged cart's Exit Port Filter and the Print Head's wick material that the filter contacts. The pressure I wish to know is present when the printer is printing some page which uses plenty of the particular cart's ink color?

Has anyone seen any references to this parameter? Has anyone done this measurement yourself?

I am thinking of how to do that measurement, and I believe I can do it, but I'd much, much rather have the answer handed to me.

 

[websnail]

I don't have any answers but I'm sure interested in any you come up with... As you've seen these cartridges are driving me scatty

 

[panos]

canonfodder, I am very interested to know why you consider them to be the best cartridges that have been made

 

[mikling]

I currently consider the Epson cartridges used in the R200, R220, R800, R2400 the best.

Why? No sponge First In First Out ink flow. Reliable consistent delivery start to finish and refillable till the rubber seals wear out. Once refilled properly you never worry about clogging or air entrapment.

Of the BCI type cartridge, I consider the Canon OEM the best as well. There is a lot of engineered details that the casual observer and purchaser of compatibles never quite notice. For example the sponge system is dual porosity. Further to that they are wedged to provide a slowly controlled density to match the ink characteristics to provide even pressure at the outlet. There is a bulge leading directly up from the nozzle that looks like it is there to limit or control ink feed from the rest of the sponge. The placement and depth of those grooves are exact to allow air to enter the tank after the upper sponge has given up its ink.The air feed system is precisely formed to allow air feed to the tank at a prescribed pressure similar to a balanced feed CISS system. The newest CLI-8 tanks further refine the design of the bci-3 and 6 and make them perform even better. There is specially designed ink delivery channel that feeds a greater area of the sponge for more even flow or delivery allied with that is a constricted neck to ensure that the feed is correct too.

I'm using the CLI-8 design where the BCI-6 was used to take advantage of the mechanical improvements but with a BCI-6 inkset.

 

[canonfodder]

Panos, Mikling is correct in the things he reports on the CLI-8 and the predecessor BCI-6 carts. I will try to fully describe what makes the cartridge so special.

The design of the cartridge gives near perfect control of the ink. The pressure of the ink as it is fed to the print head is constant and very low. In fact, one should not describe the action as fed, because the better description is that the ink is available to the print head at a near zero pressure. The immediate availability of the ink is needed in fast printing so that the print head will not be starved and result in skips in the print. The ink held in the sponge is immediately available to the print head with very little suction required to move the ink down. The near zero pressure at the carts connection to the print head prevents problems like flooding of the print head from too much positive pressure or leaking at the seal due to a large negative pressure.

Remember that these features are provided constantly, without change due to the amount of ink in the ink tank.

The lower sponge is the main source of ink while printing, and one feature it provides is the stability of the ink supply to the print head. What I refer to is that the sponge won't let the ink slosh around as will a cart with no sponge or equivalent. With low ink and rapid print head motions, the ink flow could be interrupted in a spongeless cart.

The sponge fills itself with ink due to its capillary action. It simply soaks up ink. The ink will rise in the sponge to a height where the gravity force equals the capillary force. There is no pressure pushing ink into the sponge because the ink tank, acting like a chicken feeder, only releases ink when the sponge has given up ink to the print head and can soak up some more. The bottom of the ink tank, including the passage way between the ink tank and the sponge chamber, operate at zero pressure at all times. The depth of ink in the ink tank has no effect. It is good to the last drop, with constant feeding properties.

The sponge chamber has an open air-vent port at the top. This port is where air enters the chamber to move to the air/ink passage and go into the ink tank as needed to release ink.
The vent also keeps the sponge chamber a zero pressure, forcing the sponge to only respond to its capillary action, gravity, and the suction from the print head.

The pressures at the cart's exit port and on down into the print head are constant, with only slight changes when the print head is actually consuming ink. Due to the zero or very near zero pressure at the bottom of the ink tank, the sponge chamber, and at the exit port, the print head will not be flooded with ink, so long as the cart is undamaged and it is properly sealed to the print head.

The seal where the cart connects to the print head does not have a difficult task. It must not leak ink or air, and with the sponged cart and that form of ink tank, there is very little positive or negative pressure at the seal.

Some CIS Systems have problems with that seal because they are not operating near zero pressure at that point. Some apparently operate with a distinctly negative pressure at the seal, and if the seal leaks, air goes in and the printing will not work. Some attempts at correction by way of added seals work for some users, some of the time.

 

[mikling]

canonfodder's explanation is quite good. If you dissect the Canon printhead you'll also see more details as to how the head actually functions. Once you get an appreciation for that, you quickly come to the conclusion that there is actually a relatively small tolerance for proper operation. Thus retaining the OEM cartridge and using refill ink with similar physical characteristics is important.

I've explained many times why the Canon seals and chosen method of ink feed presents a real challenge for any CISS mfr. There are two key issues... the near zero pressure and the associated seal that only seals at low pressures and the transition in pressures when head cleaning comes about.

For a CISS the Epson design is far superior but the Canon design is beauty in it's simplicity. Again, don't let that simplicity fool you into thinking that it ain't rocket science because in reality it's darn near close to that.

As to the spongeless cartridges, the sloshing around is minimized by the use of multiple chambers like the Epson cartridge. It also means that you cannot use every single drop of the ink in the Epson cartridge... in fact 20% of the capacity is pretty close to unusable because of the requirement to maintain a full chamber of ink to prevent air ingestion into the printhead. The ingestion of air will produce what most inexperienced epson users think are clogs.

 

[hpnetserver]

Well, many Canon owners had print head clogging issues despite they used only Canon OEM cartridges. I am sure Canon cartridges are great in quality. But the patents canon had on the sponged cartridges were partly for discouraging imitations.

Some 3rd party sponged ink cartridges work extremely well with a simple piece of sponge. That's a known fact existing for years already. The real problem of 3rd party stuff is caused by many small businesses trying to save cost by diluting ink, or formulating bad quality ink and feed the market with poor quality prefilled cartridges that don't work. If you have a chance to visit Southern China you will find small factories (families is the right word actually) that run the manufacturing of prefilled ink cartridges. There are tens of thousands of such operations. Empty cartridges are made in China in such a massive quantity there is no doubt there is a massive quality problems as well.

I have studied one of Canon's patent in the sponge. Believe me it is great but you do not need that kind of sponge for a compatible cartridge to work perfectly. The sponged tank could have been much smaller. The reserve tank could have been easily doubled. But Canon does not want us to have that much of ink per cartridge. CLI-8 may be a better design but it gives us less ink. As far as I know, no 3rd party manufacturers ever imitated Canon's patented sponge nor anyone has the need to infringe Canon's patent in the sponge. The patented sponge is great but it is not needed to make a sponged cartridge to work.

Canonfodder, the pressure at the junction between the print head intake and the exit hole is slightly negative. There is no pressure there. It is slightly vacuum in fact. To prove it just see if ink will drip out of the exit port before it is plugged into the printer. If there is a positive pressure ink should drip because of the pressure. When ink is consumed out of the print head it creates a vacuum to suck ink out of the exit port through the junction to supply the print head. This vacuum is fairly high actually. So the pressure at the interface is really negative, not positive.

 

[hpnetserver]

Most HP ink cartridges are sponged without using Canon's patented sponge design. The fact is you need to use the right sponge. Same can be applied to 3rd party BCI-6 cartridges.

 

[canonfodder]

Canonfodder, the pressure at the junction between the print head intake and the exit hole is slightly negative. There is no pressure there. It is slightly vacuum in fact. .......

Hpnetserver,

This is only a matter of terminology usage. I am an engineer, and whether positive or negative, they all are pressures to me, so if I say pressure, without adding the adjective "positive" or "negative", I include the whole range, with both possibilities. A vacuum is a negative pressure. A "pressure gage" may have both positive and negative parts of its scale. This is only my engineer usage of terminology. Sometimes the use of "vacuum" does add further immediate information. I can't think of the word "pressure" as being the opposite of "vacuum", though some may. Sorry for the communication issue.

 

[mikling]

Capillary action is involved in getting the ink out of the sponge and down the printhead inlet tunnels and down to the nozzle feed chambers. It has to be negative or the weight of the column of ink will drip out. Whatever the value of this "pressure" the surface tension may be a lot larger than most will imagine.

Yes, third party sponges also work, but how many have experienced ink flow problems with virgin OEM carts always being used.... I'd say near zero. Now the key question is this how many have experienced ink flow problems and then damaged heads with always virgin compatibles being used............... order of magnitudes more. Take your pick hpnetserver.

With virgin carts it's not just the ink that is the problem. Last week I lost a nozzle and a perfect head to that trying a PrintRite (reputed to be a top tier compatible) on my i950. Yes the ink was watered down and the yellow was totally wrong. But worse yet it wrecked my head. Darn.