Canon grommets - a hint

[websnail]

Something I've noticed recently with the Canon cartridges is that they all slot into a slot in the back of the printhead which helps hold them down onto the rubber grommet. Now we all know that for the purposes of a CIS the original rubber grommet isn't quite up for the task but something I've noted of late is that you really do need to make sure that all changes to the grommets (ie: replacement or addition of a thin additional silicon grommet on top) need to be mirrored to ALL the other ink posts/colours.

Why? Well it seems that changes to one tend to affect each of the others and they can raise or lower the cartridge incrementally enough that you get ink/air leakage or similar problems.


It's also worth noting that I've now ditched completely all of the replacement silicon grommets simply because they don't work properly and result in poor ink flow and even printhead malfunction owing to the pressure. This is in relation to one set of grommets I've used (approx 4mm in depth) but it's something to consider... They just don't seem to do a damn bit of good.

Instead I've been using a silicon sheeting of 0.5mm to create thin grommets for addition to the existing rubber ones and in extreme cases I've punched a set of three 1mm grommets sandwitched to create a replacement grommet. This isn't ideal though and has limited success (mainly with the PGI-5BK).. I'm looking to source some 2mm or 3mm thickness sheeting to see if that works better shortly... 4mm just creates a mess though as the hole for the port stretches out and creates a leak point.



Probably so much burble there to most people but recently I reached the conclusion that Canon Pixma's are anything but CIS friendly. :/

 

[mikling]

So in conclusion in your opinion what do you think the chances are of consumers getting long term satisfaction out of a Canon compatible CIS?

 

[Grandad35]

websnail,

I am far from an expert in your CIS, bit I thought that I would give my $0.02 anyway.

1. It is a common industrial practice to use a "vacuum grease" (e.g. http://www.coleparmer.com/catalog/product_view.asp?sku=7975130) to get a tight vacuum seal in situations like this. Google for a source of this grease in your area, but be aware that this silicone grease is sticky and is difficult to clean up (which is why it is so good at sealing a vacuum). Given that you will not be removing your carts very often, this should not be a problem as long as you are careful and only apply a thin coating. I would put a little under the rubber grommet to seal the inside of the grommet to the ink pickup, then apply a thin coat on top of the grommet to seal the grommet to the bottom of the cart.
2. As I understand your system, the sponge area of the cart is completely filled with ink. If so, the situation described by mikling can occur during a cleaning cycle. Once the vacuum rises above a certain level, the "Ink Link" between the ink pickup and the bottom of the filter can be broken and air bubbles can be drawn into the print head. Here are a few thoughts on this:
2a. A "Big" cleaning cycle should be worse than several "small" cleaning cycles spaced out over time. Unless you ask for a "Deep Cleaning" cycle, the only big cleaning cycles that you should see are when the printer is idle for several days. Therefore, running a program that prints a small test print every day or two might help.
2b. Can you run with the sponge chamber only about 1/2 full of ink? The extra air in this chamber would act an an "accumulator" and be free to expand under a vacuum. This will reduce the vacuum level in the cart, and should reduce the tendency to draw in air.
2c. Any blockage in the cart's exit filter will make this problem worse. Have you considered purging your carts to completely clean the filters and sponges and therefore reduce the pressure drop across them? If this helps, you may have to periodically repeat the purge process. When refilling, I can see a difference in this pressure drop after 3-4 refills, and it is very noticeable after 6-7 refills. This may be due to foreign material being filtered from the ink or it might be caused by the varying fill heights as the carts empty (so it may or may not be a long-term problem with a CIS).

 

[websnail]

I am far from an expert in your CIS, bit I thought that I would give my $0.02 anyway.

You know ink, cartridges, and Canons... I'm not ignoring anyone with that background

1. It is a common industrial practice to use a "vacuum grease" (e.g. http://www.coleparmer.com/catalog/product_view.asp?sku=7975130) to get a tight vacuum seal in situations like this. Google for a source of this grease in your area, but be aware that this silicone grease is sticky and is difficult to clean up (which is why it is so good at sealing a vacuum). Given that you will not be removing your carts very often, this should not be a problem as long as you are careful and only apply a thin coating. I would put a little under the rubber grommet to seal the inside of the grommet to the ink pickup, then apply a thin coat on top of the grommet to seal the grommet to the bottom of the cart.

Hmm.. interesting idea... I'll see what I can find and maybe give it a go in one printhead.

2. As I understand your system, the sponge area of the cart is completely filled with ink. If so, the situation described by mikling can occur during a cleaning cycle. Once the vacuum rises above a certain level, the "Ink Link" between the ink pickup and the bottom of the filter can be broken and air bubbles can be drawn into the print head.

Hmm... Ok, that might make some sense.. and may explain why the "problem" printer has now started working ok as air may have filtered to the top of the cartridge creating a buffer.. Hmm...:/

Here are a few thoughts on this:
2a. A "Big" cleaning cycle should be worse than several "small" cleaning cycles spaced out over time. Unless you ask for a "Deep Cleaning" cycle, the only big cleaning cycles that you should see are when the printer is idle for several days. Therefore, running a program that prints a small test print every day or two might help.

Yep... luckily not a problem in primary schools... they print ALL the time but I have the autoprint util from MIS to handle that.

2b. Can you run with the sponge chamber only about 1/2 full of ink? The extra air in this chamber would act an an "accumulator" and be free to expand under a vacuum. This will reduce the vacuum level in the cart, and should reduce the tendency to draw in air.

So the air would provide the all important buffer?... Ok, until now I'd assumed that buffer was there to stop a free flow but it sounds like that really only applies to Epsons due to their solid and better sealed design.

Right, so perhaps the best approach is to part fill the cartridges and ensure a good air buffer at the top of the sponge.. I'll give that a shot with a new kit and see how that works.

2c. Any blockage in the cart's exit filter will make this problem worse. Have you considered purging your carts to completely clean the filters and sponges and therefore reduce the pressure drop across them? If this helps, you may have to periodically repeat the purge process. When refilling, I can see a difference in this pressure drop after 3-4 refills, and it is very noticeable after 6-7 refills. This may be due to foreign material being filtered from the ink or it might be caused by the varying fill heights as the carts empty (so it may or may not be a long-term problem with a CIS).

Yeah, I had given the purge approach some serious thought but unfortunately only after filling the cartridges I have with ink.. In truth all I'm lacking are suitable ID tubing to seal around the exit port to do a thorough pull through and of course purge the system..

I suspect in the main CIS's don't suffer quite so much from the "gunk" issue as they (when working) provide a constant stream of ink and don't allow the ink level to drop and allow air to propogate algae, etc.. (well not quite so much).. The algae issue does become an issue eventually but not as much as in refilling (based on Epson experience at least).



All in all some good ideas and I really appreciate your sharing your experience.. Definitely some food for thought and possibly some solutions.. I'll keep you posted.. thanks

 

[websnail]

So in conclusion in your opinion what do you think the chances are of consumers getting long term satisfaction out of a Canon compatible CIS?

Your average consumer?.. Erm... in truth.. my advice is stay the hell away! It's too damned hard, prone to problems and frankly is going to suck badly... However I base that on my "self build" experience and not on any of the kits available for the Canon Pixma series.

If you want a CIS enabled printer, go buy an Epson C/D88 or an oldish R240 and fit that... Or alternatively think seriously about an HP K550 with a set of refillable spongeless cartridges..

 

[Grandad35]

websnail,

One more thought - it is probably necessary to install a "dip tube" in each cart that connects directly to the ink supply and which reaches down close to the bottom of the sponge. This will ensure that no air bubbles are pulled back into the supply tubing as the internal cart pressure changes (or even as the atmospheric pressure changes). This wil be especially important if the top half of the sponge chamber is left empty to act as a buffer. A second (sealable) port in the top of each cart would probably also be required to pull a vacuum to fill/prime each cart. Note that you might want to seal the "vacuum valve" with a small dollup of vacuum grease to prevent any air leakage back into the cart.

 

[mikling]

In another thread I asked if you had made sure that that a damper existed. The damper in your case is the air volume/break in the cartridge. What you must also be careful about is that the cis system never pulls back on the printhead after a cleaning. I sure sounds like you have that happening. Why? it immediately still misses after a cleaning because there is negative residual pressure in there. But after a period of non activity, the positive head from the CIS refills the head and the negative residual pressure disappears. Until another cleaning cycle comes around again.

 

[websnail]

One more thought - it is probably necessary to install a "dip tube" in each cart that connects directly to the ink supply and which reaches down close to the bottom of the sponge. This will ensure that no air bubbles are pulled back into the supply tubing as the internal cart pressure changes (or even as the atmospheric pressure changes).

For what it's worth that would be an ideal scenario but unfortunately the design of the cartridge and the parts I'm using make that a little tricky but based on what I've learned from yourselves and previous experience I'm guessing that my problem re: the buffers is two part.
1. The cis tube/supply fitting is above the sponge
2. I've been priming my cartridges via this port.

I'm also realising that I suffered from "must be full" focus when in reality the cartridge could be around half full and work quite happily so long as there's a proper seal to ensure ink, not air is drawn in to replace the ink used.

Ideally it'd be nicer to have the port/fitting above the spongeless part of the cartridge but because of the printer design it's impossible to do so without physically removing parts of the printer casing itself (hardly ideal).


As to air being pulled back that has actually never happened, the only time I get air return up the tubing is when there's an insufficient seal around the cartridge exit port.. the slight negative pressure caused by position of the reservoir bottles means that the ink is prone to flow back to the reservoir if air can get in. Were I to equalise this pressure I'd end up with a freeflow so it's necessary to maintain it but obviously not to increase it (ie: by moving the reservoirs to a shelf underneath the printer (that would be daft ).

A second (sealable) port in the top of each cart would probably also be required to pull a vacuum to fill/prime each cart. Note that you might want to seal the "vacuum valve" with a small dollup of vacuum grease to prevent any air leakage back into the cart.

As I said, I've been filling the cartridges via the supply tube/fitting and doing this by sealing the exit port, drilling a small hole above the spongeless part of the cartridge for air to escape through, and then slowly injecting ink into the cartridge via the supply fitting. (Obviously I reseal the vent hole once I've filled)

Worth noting that the top half of the Canon sponge instantly wicks away ink into the bottom part of the sponge unless you overfill (as obviously the cartridge balances out both sides of the cartridge) which I think is what I may have been guilty of with a few cartridges so reducing the actual initial fill should help and create the same buffer effect we're looking for.

In another thread I asked if you had made sure that that a damper existed. The damper in your case is the air volume/break in the cartridge. What you must also be careful about is that the cis system never pulls back on the printhead after a cleaning. I sure sounds like you have that happening. Why? it immediately still misses after a cleaning because there is negative residual pressure in there. But after a period of non activity, the positive head from the CIS refills the head and the negative residual pressure disappears. Until another cleaning cycle comes around again.

I think you may well be right about this regarding the overfilled cartridges but as noted above, there's very little negative residual pressure.. Where I think I've probably gone wrong is in using tubing that it too thin for the purpose and this has increased the vacuum overpressure effect you noted.

I'm slowly rebuilding all my kits to the original configuration I built on my first two iP4200's.. with 2mm ID tubing (Tygon) and larger ID fittings on the cartridges as this is working without problems on all the kits I installed it. Taking into account all the point raised above to ensure a better air gap, creating my own 3mm grommets, etc.. I think I'll probably lick this.


If anything I suspect I've been guilty of trying to change too many variables at once when my first kit was working well within tolerances and then trying to fix them all in one go.. Never works and I should know better.. Such is life..

Anyway, for your info', the kit I reverted back to the wider ID tubing has just run a cleaning cycle and is now printing with a barely discernible left to right fading effect so it seems that the tubing does affect the tolerances.. That and I've realised that the replacement Magenta cartridge I installed on the kit (the magenta was showing the most pronounced problems) was run as a standard cartridge for a while (without tubing attached) so the buffer would have reinstated itself naturally as ink was used up.

I guess you live and learn..

 

[websnail]

Right.. I'm starting to feel like I have a new set of rules here having completed a new kit for an iP5200 and a re-build of my MP830 printer.

As in the post above I used the 2mm ID tubing and whilst it was something of a chore to try and work out how to get the tubing into the printer it has worked perfectly. Along the way though I learned a few things.

1. If you put a thin grommet in on one cartridge you have to do it for all of them.. If not the theory I had initially holds sway and the cartridges either side of the most raised will suffer ink starvation due to the slight imbalance caused by the out of kilter grommet/cartridge.

2. The air buffer issue is definitely part of it and reducing the ink level in the cartridges, allowing to settle and then reinstalling in a CIS helped enormously

3. The inner diameter of the tubing is also a big factor.. The thinner tubing was just not up to the job, you need something around 1mm ID or more to do the job.


So, all in all, not a bad days work.. Thanks for the input guys.

 

[Grandad35]

websnail,

A question - do you also completely fill the ink chamber? This should help to stabilize the ink level in a partially filled sponge chamber, since ink from the ink chamber can replenish the sponge chamber if its ink level drops. This should allow several CCs of air to leak into the cart before the level in the sponge chamber drops too low.

It's good that the thin grommets are working, but keep the vacuum grease in mind if you still see air leakage over the long term. Vacuum grease will provide an almost perfect seal and should last almost indefinitely, as long as the carts aren't disturbed. It also doesn't require the extra seating pressure required with the extra grommets, and won't distort the print head or head carrier.