Re: 3D printing, powder spreading

I remained with thermal-droplet inkjet technology (Canon/Lexmark/HP),
more because I had those printers around. It was more luck than a
conscious choice. I wanted just a b/w inkjet - I've also used the
color ZCorp units, but everyone I've spoken with that has them shares
the same opinion - the extra $30K wasn't worth if to print in ZCorp's
colors, but it was worth it for the larger build area. I still had no
desire to print in color so didn't want the hassle of color heads on
the machine. I found an old portable HP deskjet, but the internal
structure was not conducive to hacking apart. My best luck (current
unit) was from a Lexmark (color, doh!) multifunction print/scanner -
to my joy the unit didn't throw up an error flag when the flatbed
wasn't connected. It was pretty simple to get the order of paper-in,
paper-out to happen, as the sensor they used was a paper position, not
paper-out - but it made the "pause and replow the layer" requirement
easier in the long run. I'll dig out some early pix, and shoot some of
the existent box, too. The "existent box" is still in development -
I've printed layers, but no finished parts yet - not enough time to
dedicate to the fun side of RP (my mill is actually making me money,
and I need to try and keep it that way!)

Just like the commercial unit, I emptied the print head of it's ink -
I think I got lucky with the Lexmark; one older HP head I opened up
had a pressure reservoir with a spring (56 type head, IIRC), which
wouldn't have been a clean plumbing job. The Lexmark I just put a
10-32 fitting in the top and plumb to my
watered-down-Elmer's-BROWN-glue tank (poly fuel tank for RC
airplanes). I do pressurize the tank slightly with a mini air pump,
but I don't think it's really necessary.
The commercial unit does use a pump (inline) and the HP 10 printheads
do get very upset if there is a bubble in the feed line. HP made the
#10 heads to attach to an external reservoir or tank. The heads were
originally designed for a large format (tabloid? roll?) deskjet. It's
actually difficult to find them without going online or special order now.

ZCorp runs their ordering system online, and you need to be a
registered member, with a printer serial number to get in. Besides,
who would want to pay $1200 for 88lbs of plaster? We even added water
to it - it sets up just like real plaster. Not kidding!

The plaster will set with just water, but plain water drips and seeps
- it's viscosity is too low. IIRC, the plaster also goes highly
exothermic in a water-cure reaction and shrinks. With a water-glue
mix, you can add less fluid to the powder to get it to stick, thus
reducing the exothermic reaction. I recall that there is a setting in
the build program that allows you to account for anisotropic(?)
(non-linear 3 ways) scaling, so shrinkage could be controlled.

Given the above, the piezo may function better; I've not had both to
compare with...

Ted.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "dandumit" <dandumit@...> wrote:
>
> laserted007 - could you give us some more details ? Maybe a picture ?
> What make of printer is and What ink are you using ? ( original
> HP/Epson inks ? )
>
> I have found some while ago 2 links about modified inkjet printers :
> http://techref.massmind.org/techref/pcb/etch/directinkjetresist.htm
> http://techref.massmind.org/techref/pcb/etch/cx4200-vs.htm
> The second one contains also a small schematic and source code for
> fulling the printer that is working with normal paper.
> I think that this could be used as a start and to this could be added
> the Z axis.
>
> Are 2 questions remaining until we can experiment :
> 1. what ink could/should be used ? (I think that epson is better for
> testing because it's using piezo technology and it accept a wider
> range of inks. it has by default an ink which is water resistant).
> 2. what powder and hardening agent should be used ? and I think that
> this is the key for experiment success.
>
> Maybe we can buy original consumables from Zcorp ? I wonder if they
> are selling consumables even if you aren't a printer buyer.
>
> Daniel
>
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