How Many Psi Is Save For A Printhead?

[Smile]

How many PSI air purge is save for a Canon, EPSON ,HP printhead?

With water I know it must be low, I'm told 1psi but isn't that too low? Fot 5pl or so nozzles for eco solvent/solvent ink heads they use like 8psi. So it makes sense that for smaller nozzles you must use lower pressure.

But what about air? Some said they used compressed air, compressor etc. And print head survived

 

[turbguy]

Isn't the object to produce flow? The lower the pressure, the better.

I doubt that a thermal print head operates with more then an inch or two of water pressure head.

 

[Smile]

While "steady stream" is enough pressure for water, you can't verify so by using air.
So that is why I ask, air is more easy to go trough the nozzles.

 

[Grandad35]

How many PSI air purge is save for a Canon, EPSON ,HP printhead?
.....<snip>...But what about air? Some said they used compressed air, compressor etc. And print head survived

Keep in mind that the actual nozzles in a Canon print head are located in a thin (ca. 0.25mm thick) ceramic substrate that is quite brittle. I have used compressed air to blow out the nozzles and a syringe to push/pull water and alcohol through a Canon print head. However, I have also created at least one channel-to-channel leak when doing this. I now limit myself to the pressure that I can generate by mouth when blowing through a Canon print head. If the nozzle plate assembly is removed from the plastic body, then you can use full line pressure on the plastic body.

I doubt that a thermal print head operates with more then an inch or two of water pressure head.

In operation, the exit of the nozzles is at atmospheric pressure, so it would appear that the head operates under a slight vacuum and uses capillary action to pull the ink from the cart.

 

[Smile]

I thought maybe somebody measured pressure with manometer or something.
I'm building a "print head doctor" DIY, and was just wondering what AIR pump to get. I'm going to use pump, container, programmable pressure valve. For water I'm use vacuum/pressure type water stainless L316 -30inHg to 30PSI valve (graded 0.5PSI).

As there will be relieve valve on the line the pressure will be under control.

I tested the manometer with 20cc syringe and just simple rubber hose that I had trouble sealing as I don't have fittings yet. The MAX pressure AIR was 18PSI, so at least with air I think it's safe to go 30PSI.

 

[turbguy]

I use a "Turkey Baster" with a hand bulb to force air into the ink inlet and through the nozzles. The plastic tip on the baster is easy to modify for a good fit around the inlet, and I estimate I can't generate more than 5 psig using the bulb...seems to work for me for the few times I have used it. Cheap, too!

Wayne

 

[turbguy]

In operation, the exit of the nozzles is at atmospheric pressure, so it would appear that the head operates under a slight vacuum and uses capillary action to pull the ink from the cart.

I believe there is a slight pressure upstream of the nozzles, as the ink channel is full of fluid all the way back to the cart. With a full cart, that's an inch or two of water. "Surface tension" at the nozzle openings prevents a gravity-driven flow through the nozzles.

At least, that's my theory....

Wayne

 

[Smile]

With a full cart, that's an inch or two of water. "Surface tension" at the nozzle openings prevents a gravity-driven flow through the nozzles.

I agree, because if I use liquid cleaning mix with ammonia 10%, isopropyl 90% (no additional water). The mix even pours trough the needle from a syringe, very high viscosity mix. If I use that in cleaning the head the mix flows so fast that a few deep purge cycles will almost empty the carts.

You can see how print head doctor works on youtube, the company that sells them has a great amount of various videos to show that it really works. It's only for solvent wide format printers and very very overpriced. So I decided that automation and pressure control is good thing to have, and decided to outsource some parts.

I have most of the needed parts except I'm undecided on:

Pumps for water
Pumps for air
I don't have joints yet
I must buy the valves and some filters etc.