HP 940 Printhead problems..!

[Pcarsba]

Update: An empty dry HP940 print head weighs in at 42 grams. Some of the ink is trapped in the chambers covered by the double-layer paper filter screens. You can take these out and later re-install. I removed them with a small flat screwdriver. They are wedged in place only. Once the filters are removed all ink will drain out easily.

I filled a head and it weighs 62 grams once the initial weeping through the nozzles stops. That amounts to ~10ml of ink for each color. Weight seems to be one good health indicator for these heads.

The nozzle chip is a Si substrate with a V notch for each color. It has lots of electronics. The ribbon cable connects to it at either small end. The bottom of the V-notch is closed with an orange transparent film (outermost layer of the print head) and there are capillary channels to the nozzles. There is a double row of nozzles for each color. The orange foil is sensitive and can get damaged easily leading to a leaking head.

 

[ink-solutions]

I am going to try ink from a next supplier. I have ordered them already. I will see if its the ink thats killing my print heads.. I just cant see how come because the printer uses pigment ink an my CISS is dye.. I will just try some other ink.. What you all think ??

 

[Pcarsba]

No doubt it is the ink. Low-quality pigment stuff killed mine. All four colrsceventually clogged. Never again Nanodigital.!!!

Here is another interesting observation. Most times the yellow is what depletes fastest and the reason is simple: Even with stock ink it is the black that tends to clog first. And that results in sucking twice the amount of yellow ink out of the heads (compared to the other two cors) when the printer goes into its cleaning frenzies. The printer has two suction cups that draw ink but they are connected to the same vacuum line. With black clogged shut it is lots of yellow flowing from the K/Y head. The printer can not just apply suction to the clogged color. And so yellow will get drained more.

My dye black im the HP940 doesn't live up to the pigment black. I am thinking of experimenting with a 50:50 mix next, maybe that'll deepen the color without clogging so quickly. Just have to make sure both inks' chemistries are compatible. We'll see.

 

[ThrillaMozilla]

I am thinking of experimenting with a 50:50 mix next, maybe that'll deepen the color without clogging so quickly. Just have to make sure both inks' chemistries are compatible. We'll see.

Betcha they aren't. I wouldn't even think about it. But you could try. Mix them and drop some on a glass slide. Then if you still think it's a good idea, draw some out on paper with the glass slide.

The problem is that you may cause flocculation of the pigment. That would not be pretty inside your print head.

 

[ink-solutions]

So are you guys saying that their is no good pigment ink out their that will not clog the heads ? i found a supplier in china, claim to have very good specified ink.. I am going to give them a try..

 

[Pcarsba]

What's the name? ND is all over eBay and Amazon but clearly doesn't work. It's from China, too. I am curious. I read here that even OEM black seems to have a tendency to clog. That leaves me wonder - if HP is struggling to get this to work reliably what are the chances a cheap third party offer nails it?

 

[ink-solutions]

So its best i just stick with the dye ink.. but i want a good dye ink that will not clog print head.. any idea ?