How close of a colour match should I expect 3rd party inks to be?

AndrewB

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Well even before I can get my spectrophotometer I've more or less given up on this CISS system. I was about to print a calibration target for profiling today but did a nozzle check first. I saw that I had the same two nozzles missing as I had from the last time I printed (3 days ago) so decided to try a cleaning cycle. It was a disaster, post cleaning cycle some of my colours were completely absent and the rest were less than half working! The last time I ran a cleaning cycle (three days ago) it worked fine.

And this is already with the ink tanks elevated 48mm, which seemed to be required to prevent nozzles from progressively dropping out during printing. I'm kinda shocked that people could sell something that works so poorly actually, I've printed well over 100 test pages and nozzle checks in the last week or so and haven't once had a nozzle check at 100% despite everything I've tried.

I think I'm going to have to take my medicine and switch back to cartridges if I ever want to use this printer again. I'm an engineer by day, so it really makes me miserable when I have a consistent problem that I can't solve and this one is driving me crazy.
 

Ink stained Fingers

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I'm an engineer by day,
there is some more to inkjet printing than looking to some static pressure situation, it is hydrodynamics/acoustics at its finest , just think at the Navier-Stokes equations for a second, or read this thesis for some more of that


having absolutely no air in the ink lines or dampers

Be aware that dampers serve a purpose as its name implies. There is an effect - easy to understand - that the pressure in the tubes depends on the direction the head moves - the head is either moving against the ink flow ro with the ink flow depending on the printhead speed and direction. You don't have this effect when the cartridges are travelling along with the printhead. An air bubble supported by an ink chamber covered with a foil can lower these pressure changes.
And there is an acoustical effect - there is a pressure wave propagating backwards into the ink reservoir and the tubes - and if you have an air bubble in the damper you have a completely different impedance, so as a general rule dampers should be filled partially to have an air bubble buffer there for these and some more effects.
It's amazing at the end that it's all working that great as it does.
 

AndrewB

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Thanks, I'll have a look at that paper and I'll try to allow some air into the dampers to help damp out pressure pulses from nozzle firing and head velocity. I actually worked for a while at a company making production line machines for the assembly of inkjet print heads, although never design of the heads themselves.

I know that generally speaking the print head is designed to operate at a slightly negative static pressure to prevent flooding of ink out the nozzles, which is why these CISS systems typically have an effective ink level quite a bit below the head and they always caution about raising the tanks. I've attempted to raise the tanks to just below the head which made a large improvement but obviously still not enough for reliable operation. What confuses me is that normally the OEM cartridges ride above the head and are open to atmosphere, so unless there's some loop of tubing below the head I don't see how they could provide a negative static ink pressure, surely it would always be slightly positive? The CISS would definitely be supplying a negative pressure as the damper is sealed and linked to the storage tanks, which are significant below the level of the damper.
 

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There are a few more and simpler reasons why a CISS does not work properly. It could be that there is a problem with the cartridges in the printhead the CISS most likely is using, they may impede the ink flow, they don't seat properly because of mechanical tolerances, the valve is not opening at the ink outlet, the airflow into the cartridge is blocked inside from a bad molding/manufacturing process , I have seen a lot of such things. You may disconnect the tubing and just test-print with the cartridges, with the remaining ink inside - for a short while to see if that changes anything. This would allow you to separate the areas - tubing - ink supply - from local effects with the cartridges. I did this several times - replacing mal-operating cartridges with properly working refill ones, and just swapped the chips if needed.

The issue with the pressures changes from the printhead movement already came up long time ago, I think it was with the R2100 when people tried to install a CISS at that time, the simpliest solution was easy - to disable bidirectional printing - but with the negative effects on printing time. But this woul not solve any other CISS problems. When you look to some Epson larger format printers you'll see that the cartridges, with bags inside, are slightly pressured during printing to improve the ink flow. There are other tricks to overcome this problem - to feed the ink to the printhead from both sides - with 2 lines of tubes.

The dynamics in the printhead - ejecting the ink - create a pull effect at the other side of the tubes in the printhead, a printhead, the nozzles typically can pull about a few centimeters of liquid level. The nozzles are that small that ink just won't drop out - surface tension etc.
Canon cartridges typically use some foam in the cartridge, even more than one layer, which prevents the ink just to flow out, and Epson genuine cartridges use a membrane valve to hold back the ink if the nozzles are not pulling ink via a low underpressure. Refill cartridges don't use such system , they exploit the capability of the printhead that it still can operate with an ink level just above the nozzle level, and when you look careful you'll see that the air channel in such cartridges goes to the bottom of it to prevent that a varying ink level may have a further detrimental effect.

So yes - there are a few completely different reasons why your CISS does not work properly.
 

AndrewB

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Hey all just an update, eventually gave up on the CISS and converted the system back into re-fillable cartridges by remove the ink lines and draining the air intakes down to the level they should normally be. This seems to have instantly fixed all of the issues I had been having, for the first time since installing the CISS I got a full nozzle check and have proceeded to use my colormunki to profile the printer. I printed a test page and it now matches the manufacturer's colours pretty much as good as my eyes can see.

I also noticed some minor banding in areas of solid colour and did an alignment check of the nozzles, which showed that most of them were off to some extent. I hadn't done one since getting the printer so either they were off from the factory or I knocked the head slightly in all the playing around I've been doing.

Either way seems like I'm finally back to a fully functional printer. Now I just need to figure out how to refill these cartridges without any long needles, we're under total lockdown here so no shops are open and no parcels are being delivered. I have plenty of syringes but no needles.
 

AndrewB

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I have one small question now which is a bit off-topic for this thread. I just made a profile for Ilford gold fibre silk baryta paper and when I made my test prints for generating the profile I selected the "lustre" media type in the Epson driver. However now I realise that Ilford's profile for that paper and my printer say that you should use the "glossy" media type.

I think it's best that I use the "glossy" media type from now on as that's what the paper manufacturer recommends, but can I keep using the profile I made with the "lustre" settings? Or should I make another profile with "glossy" media type.
 

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You could actually answer this question yourelf by creating a profile with the glossy media type and then compare the gamuts - which one is larger - which one gives you a better black level - I don't know, I can tell you from my own testing that the media type setting can have an impact on your profile - yes, and that's the reason why I do profiles with several settings - media type and quality level. The quality level setting can make a difference as well, general
statements are just not possible - every driver+printer behaves differently , I have seen quite significant differences on one printer model, and virtually none with another printer between different quality settings.
As long as you use a 3rd party profile - Ilford in your case - you should use that media type they used to create the profile.
 

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That was quite some primer on CIS systems @Ink stained Fingers :bow

You might want to write that lot up as an article as it contains a lot of key information that should be going with CIS systems for Epson pigment printers.
 

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