Canon grommets - a hint

[mikling]

Yes, the head carrier is not made to carry high loading by the seals. Don't permanently distort the carrier. I imagine bad things can happen. Try the grease seal before the oversized grommets.

 

[websnail]

Yes, the head carrier is not made to carry high loading by the seals. Don't permanently distort the carrier. I imagine bad things can happen. Try the grease seal before the oversized grommets.

I can confirm this quite explicitly... Having put a couple of the replacement silicon grommets in a number of printers I've pretty much pushed at least one maybe two printheads beyond their tolerances.

More than a little annoying as these grommets were being sold with commercial ip4200 kits up until 2 months ago.. Beyond that it's also pretty obvious that use of any kind of "wedge" above the cartridges is also a bad idea as this has the same kind of effect.

Agreed about the vaccum grease and I'll be sourcing some, I'm just aware that I've made the mistake of assuming the grommets were the primary cause when there's been a lot more at work so I'd rather get everything else tweaked before I tighten/tweak up the grommets to close the last loophole.

 

[canonfodder]

I've been reading all this thread with great interest. A few days ago I received a new CIS system to install on my iP4200. This system is sold on eBay by a person whose ID is cis.supply.hk. Yes, he is in Hong Kong. The system is sold under the name CIS. Ink Supply, and it looks to be very well made.

Why this thread is so interesting to me:
This system is shipped with the now dreaded "replacement silicone seal pads". The pads are translucent and not foam. They seem to be of a fairly low Durometer, and my guess would be around 20 to 30. The instructions say the replacement pads are "to overcome the slight design fault in Canon printers. In short it prevents air getting between the cartridge and print head.(due to Canon's raised print heads)."

So with all the discussion of the seal pads in the thread, I am wondering just what to do. I am leaning toward leaving the original seals in place but adding Grandad35's suggested vacuum grease below and on top. Before proceeding, I plan to do some measuring of the original pads and the replacement silicone pads supplied.

When I look at the original pads in my printer, I see a neat circular depression left by the cart's exit port. I haven't pulled out a pad to examine it more closely. Will I see a sponge form of rubber or a solid form? If it is sponge form and the effective Durometer is fairly low to very low, I can imagine that any distinct vacuum could create an air leak. This points out a distinct difference between the original ink carts and a CIS system. The CIS could create a definite vacuum which the Canon carts do not. An OEM Canon cart with its air vent right into the top of the sponge chamber probably produces essentially zero vacuum in operation.

I have studied the physical details of my new CIS system, and find that the claimed "Air Balancing System" is the well known 'Mariotte Bottle' arrangement, http://lawr.ucdavis.edu/classes/ssc100/mariotte_bottle1.pdf , which can maintain a constant pressure, either positive or negative at the ink outlet point, depending on the elevations of the air inlet point down inside the ink tank and the ink outlet point. I measured these elevations of this CIS system and my printer, and if you consider the print head output level as the output point, the pressure exerted at that point should be negative, thus it would be on the vacuum side all along the system through the cart-to-head interface, the dummy carts, and the tubing back to the tanks. The print head output is about 2.3 inches above the air inlet point in the ink tank.

The seller's sales pitch page brags about "no more air filters needed", and with the "Air Balancing System" included, I thought that a new and different arrangement was in use. Not really so. As I said, the Air Balancing is the Mariotte Bottle, and that requires air inlet ports which this CIS has, and there is simply no air filter on the air inlet ports. Perhaps it could use a simple filter there to keep out air-borne dust and tiny bugs. Maybe I'll just drape a clean handkerchief over the ink tanks. The air inlet ports are on the back side of the tanks, up near the top.

The dummy carts used in this CIS are spongeless but there is a very fine filter within the cart's exit port. It appears to be similar to Canon's. Grandad35 suggested such filters were the same as filtered cigarettes use.

I purchased the CIS system as empty, no ink supplied. I did not want to change from the MIS supplied Image Specialists ink I now refill with to some unknown ink from China. I had to communicate with the seller to get the procedure for the initial filling with ink as the supplied instruction sheet only dealt with a system as shipped already filled with ink. The seller has been very quick to answer email inquirys, and his english is not too bad. I have writtten out the initial filling instructions for my own records.

I will be reporting on my installation with words and photos. First I have to decide what I will do about the seals.

 

[websnail]

This system is shipped with the now dreaded "replacement silicone seal pads". The pads are translucent and not foam. They seem to be of a fairly low Durometer, and my guess would be around 20 to 30. The instructions say the replacement pads are "to overcome the slight design fault in Canon printers. In short it prevents air getting between the cartridge and print head.(due to Canon's raised print heads)."

So with all the discussion of the seal pads in the thread, I am wondering just what to do. I am leaning toward leaving the original seals in place but adding Grandad35's suggested vacuum grease below and on top. Before proceeding, I plan to do some measuring of the original pads and the replacement silicone pads supplied.

I'm more than a little surprised that you've been sent the old style of silicon replacement pad as the review kit they sent me was one that included the newer thin silicon pads so I naturally assumed that the seller had realised it was time to move on.

Couple of things to note really..
1. The replacement grommets I got (40 sets in all) had very poor quality control with at least one set in every two being ditched due to tool marks, flashing or cuts that would compromise the seal.
2. The grommets are significantly deeper (or at least mine were and it's the same seller) and do require a reasonable amount more pressure compared to the thin add-on seals.

I can't say with any certainty that the seals won't work with the full HK CIS kit (I've still not got around to installing mine) but having been round the block I'd recommend a little caution, check the quality of the grommets you have been sent and query the seller to find out why you've been sent the old style instead of the newer ones.

In the mean time if you want, PM me your mailing address and I'll pop a few homemade thin 0.5mm grommets in the post for you as I've pretty much perfected my technique for making these and they work a treat. That and the $4 a set cost I've been getting quoted from source is just stupid when you consider how little they actually cost in materials.



Oh and as for the Canon originals... well the rubber grommet consists of about a 1mm solid top layer of rubber over a hollow section that gives it an overall depth of around 3mm. The design seems to allow for a little give so that the cartridge seals relatively well against the grommet and maintains a seal around the printhead ink post. For the purposes of a CIS it works ok most of the time but as pointed out re: pressures, etc.. it doesn't quite do the job and will leak in some cases (I do have a kit that doesn't have any grommets but that's the exception) so an added .5mm grommet tends to provide the better seal. In some cases it seems that putting the silicon grommet under the rubber one works best but only if the silicon grommet is a good fit.

 

[ocular]

Grandad thanks for the tip on vacum grease. I have come across various types of goo like this, rubber grease, teflon grease. Dow Corning make one that should have the right properties,

http://www.ellsworth.com/display/productdetail.html?productid=403&Tab=Vendors

Canonfodder thanks for your feedback on your recently installed CISS. It does seem to confirm my observation that the CISS spongeless cartridges have a need for much more predictable pressure head from the ink reservoirs and thus have the Mariotte system.


A further observation from my recently installed CISS ( see http://www.nifty-stuff.com/forum/viewtopic.php?id=1745) is there is a difference of 6 cm from the top of the ink in the cartridges to the top of the ink in the ink reservoirs (when full). This is a non mariotte system. This is when the external ink reservoirs are place on the same surface as the printer. This means that is a column of 6cm that pressure has to rise to pull ink into the ink cartridge. I have now setup the external ink tanks so that the level of the ink is 2 cm below the level in the cartridges thus reducing the stress on the seal between the cartridge exit port and the printhead. There should be still a reasonable safety margin as this gap will increase as the ink goes down in the ink reservoirs but stays the same in the ink cartridges. I think that if one can titrate this level that significant reduction in the pressure across this well documented weak point can can occur. However be warned moving the level of the ink tanks so that they are too high will cause a siphoning of ink into the printer!

 

[mikling]

Float your ink tanks in water. Individually is best. That way as the ink depletes, the tank rises to compensate and this produces an even pressure head. You do need to maintain the water at a constant level but that is simple. This is known as Archimedes principle.

 

[websnail]

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.

Thankyou, thankyou, THANKYOU!!

I finally managed to source some silicon grease via good ole' Google (ie: "Rocol Sapphire Aqua Sil") and it has done the trick a treat.

The way I've done it is to apply a thin coat to the underside of the original rubber grommet and then applied another thin coat to a thin silicon grommet that has been added on top of the rubber one. I didn't apply any to the cartridge exit port but that may be as good as the silicon grommet.. either way I chose not to go that route to reduce the possibility of messing up a cartridge exit port (me = clutz at best of times)... Results were printouts that shows very little ink starvation banding or similar issues so it seems to have done the trick.


Just to recap though it seems the winning formula here is the following:

- Remove the existing rubber grommet carefully
- Apply a small amount of silicon grease to the underside of the rubber grommet
- Replace rubber gromment being careful not to smear any grease on the ink post
- Repeat as required for other grommets
- Apply small amount of grease around exit port of each cartridge
- Insert cartridges as normal
- If necessary add a thin silicon grommet over rubber one, applying a thin layer of grease between rubber and silicon grommet


All in all the key thing seems to be the seal and not pushing the cartridge too far away from the ink post.. And for some bizarre reason the Magenta will be the pain in the butt.. Still trying to figure out why but that's my experience (Image Specialists for those wanting to compare)

 

[websnail]

Seems I spoke too soon...

The seal worked well for a few weeks and then when I went back to check output on a couple of printers I found the problem had returned..

I've also discovered that the problem shows itself in different ways on different colours..

Cyan and Black are showing a horizontal banding effect and yellow will start to fade as it gets used up.


All in all I'm figuring that the problems I'm seeing are the result of multiple testing (ie: removal, fiddle, replace) and the printheads are just not handling the abuse too well... Either way, I'm not overly pleased with the way things have worked out on 4 of my 12 Canon printers but it's been a learning curve that I'll put to good use when I build a new kit from scratch with new printhead, cartridges, etc...

 

[canonfodder]

Websnail,

On another thread, you said that you would publish photos and explanation of just how your self-build CIS units were made. I hope you get time to do that someday soon. Meanwhile...............

This thread seems appropriate for a question I have been wanting to ask. Mikling mentioned floating your ink tanks in water to keep a constant "head", or ink level.

Do you think a significant improvement would result if you could keep the top of the ink in all the CIS bottles at a level that was even with, or perhaps just a bit below, the cartridge exit port level?

The idea I am pursuing is that operation might be better if there was little or no vacuum required of the printhead. I think your printheads must be pumping to pull ink uphill from the CIS bottles. This of course is not how the OEM cartridges operate. They do operate with practically zero pressure at cartridge exit port. If there was little or no vaccum required, the issue of the seal and air leakage problems might be lessened or eliminated.

What do you think?

 

[websnail]

Reservoirs in the water?!... Why the [expletive] didn't I think of that!... Genius!.. Of course you'd have to figure a way to make sure the reservoirs didn't tip over, etc... but I have to say I love the simplicity... it certainly deals with a number of issues quite nicely..


Oh and thanks for the reminder about the photos.. I'll sort that in the next couple of days.