What I've learned about ink staining - Heads Up!


#1

Hi all,

I’m in the process of getting my 7900 (with a mostly dead Green channel) loaded with my new PiezoPro inks. In my planning for this conversion, I made the decision to do a full PiezoFlush of the machine before loading the inks, and well, I have to say I am REALLY glad I did.

I loaded a full set of carts with PF and did the INIT FILL followed by a Nozzle Check. My nozzles were all good, but as I expected I did notice some staining. Since it is very difficult to really see the full extent of staining with a nozzle check print, I decided to run a 100% density print of all 10 colors together on one sheet (using QTR) and here is what I got:

After PF INIT FILL

There is obviously a LOT of color ink still in the system, and not just Yellow. I was especially surprised at how much Cyan and MK were still present. I knew that some staining was to be expected, but this much was not expected! In the image, the Orange bar is my target for all the other colors since I’ve had PF in that channel for some months now. The Green channel has also had PF in it for the same amount of time but it is slightly lighter because of the missing nozzles.

Having seen this, I will NOT proceed to load the PiezoPro inks until I see all pink on this print. I’m proceeding to run purge channel prints on the stained channels using the QTR calibration mode as documented on InkjetMall. So far it is taking a lot of printing to begin to see change towards pink, but at least I do see it slowly moving in the right direction. I may consider a 2nd INIT FILL with PF to move this along more quickly.

My take from this is that the staining topic is not given enough emphasis in the docs regarding printer conversion to Piezography. Yes, it is mentioned, but my experience suggests that you will have MUCH MORE staining than you might think. This also has implications for when the real inks are loaded and another INIT FILL is done to purge out the PF…I am expecting a LOT of printing with the new inks before I get rid of the pink!

FWIW, Dave


#2

A few quick thoughts.

  1. PiezoFlush likes to site for 48 hrs after init-fill. One power clean on all channels after this sit will clear a lot of the final excess pigment that you are seeing in the channels.

  2. You may have a damper/cleaning assembly that is not sucking as much fluid as it should. After an init fill, it shouldn’t look this saturated at all. Check your fluid levels in the cart. I suggest marking levels with a sharpie before each init-fill in future as well.

  3. It may just be very old dampers that have a lot of excess agglomerated pigment. The flush will slowly degrade the agglomerations over a long period. I suggest letting it sit for a few days if possible.

cheers,

Walker

 


#3

Thanks for the comments Walker.

In the end (in case anyone else is following this thread), it required three INIT FILLs with PiezoFlush to get my 7900 to an acceptable level of pink in all channels. Maybe I’m being a bit obsessive about getting the staining out, but I really want to start with PiezoPro Ink and nothing else being printed as I get my workflow established and especially if I do any linearizations.

While the suggestions regarding the ink selector and pump/cap as being possible contributors to the extensive staining are certainly valid, I have concluded that the main problem is simply accumulated ink on the walls of the ink tubes running from the carts up to the selector/head. I made regular observations of the ink tubes all along the path inside the printer as I was doing each INIT FILL and after the first one, the Cyan, MK, and PK tubes were still very dark and the Yellow tube was still yellow. After the 2nd INIT FILL, there was a big improvement, and after the 3rd INIT FILL, all the tubes are nice and pink and my test print looks acceptably pink in each channel.

I’ve decided that the next time I convert one of these large format Epsons to Piezography I will order a new tube set and replace it as part of the conversion :-). It should make it go a LOT faster and require a lot less flushing. My next step is to replace my pump/cap assembly with a new one I’ve had sitting here for a while, then get the new inks loaded. Onward…

Dave