Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "fenrir_co" <fenrir@...> wrote:
>
> --- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
> <stefan_trethan@> wrote:
> >
> > Do you know if it is posible to make a spongeless cart from a spongy 
> > one?
> > I don't really need a CIS, but i need something i can refill easily 
> > inside  
> > the printer.
> > 
> > ST
> > 
> 
> No. The spongeless carts have the air vent specially designed to keep 
> enough negative pressure to keep the ink in the cartridge. The sponge 
> is specifically there to prevent leaking. If you took the sponge out, 
> all the ink would drain into the printer.

Actually it's the sponge that creates a virtual negative pressure. The
air vent allows air to refill the cartridge to ambient pressure, not
negative.

Dump some water on the table, it runs all over. Pour it into a sponge,
it stays in the sponge. It is at ambient pressure, but it is as if it
were at a slight negative pressure, keeping the ink from draining
right out when the cartridge is not installed. However, once it is in
the printer and properly primed, this virtual negative pressure is
lessened.

Spongeless Epson cartridges have a different arrangement, with valves
only opened by the ink spike. In addition, internal structures
regulate the pressure down to a low, but not negative, value. As
someone else pointed out, surface tension at the nozzles keeps the ink
from running out against this very small pressure.

Steve Greenfield