Re: [CAD_CAM_EDM_DRO] 3d printer binder supply

Cartridges are more complicated than you might imagine :-). At any rate, there are a few things to consider. The ink stays in the cartridge due to "back pressure", basically an upward pull on the ink provided by a sponge. For these cartridges this pressure amounts to about 1" of water - you will need to supply binder at a level that approximately matches the middle of the cartridge to avoid causing "drool". If the supply is too high (more than an inch or so above the cartridge) binder will drip from the nozzles. Too low and the cartridge will not take up binder from your supply. Viscosity is not terribly important, the cartridges would probably work filled with water. (High viscosity may be a problem as the channels in the printhead are very small and may be easily clogged with high viscosity liquids). You will need to prime the connecting tube and will need some method to provide a fluid connectivity. It may work to provide a tube with a needle (something like an air needle to fill a basketball) inserted into the foam, make sure you have a good seal to the tubing and back to the supply. Avoid puncturing the filter screen at the bottom of the foam.

The 21/22 cartridges are designed for a rather small ink volume. Do not overfill them as this can cause them to drool. It would probably be instructive to cannibalize a cartridge to get an understanding of the internal construction.

The color nozzles are smaller, the color drops are about 1/3 the size of the black drops. You may have better luck using the black cartridge if the binder tends to clog the color nozzles.

Regards,
Bob Headrick (an ink cartridge designer in a former life....)

----- Original Message -----
From: Graham Stabler
To: CAD_CAM_EDM_DRO@yahoogroups.com
Sent: Thursday, May 31, 2007 12:30 PM
Subject: [CAD_CAM_EDM_DRO] 3d printer binder supply


The HP21/HP22 cartriges are super simple, they are just a box with
some sponge in. The filler hole is covered by a sticker, I read that
they will work with the sticker removed too.

The idea is to just add a tube to the top of the cartrige and connect
this to a little tank allowing gravity to feed the ink.

BUT, if I add a tube and seal it to the cartridge and assuming my tank
has a breather tube will binder travel into the cartridge simply due
to the fact that ink is leaving by the nozzles?

Should I prime the supply tube?

Also does anyone know a simple way to measure viscosity, I don't know
what I am going to try feeding into the cartridge but I'd like it to
seem as much like ink as possible, I'm fairly sure water like
substances just drip out of the nozzles.

Graham



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