Re: Homebrew RP?

Message: 2
Date: Sun, 18 Jul 1999 10:06:12 -0400
From: Randolph Lee <boss@...>
Subject: Desktop Rapid Prototype

As far as I know there Are only a few companies doing Desktop Rapid Prototype

I saw one of them in action a few years ago At EasTec...
http://www.sanders-prototype.com/main.html
It does work like (and is about the same size as) an inkjet
printer... putting down 2 types of plastic (for the part itself and
for the undercut support... that latter can be dissolved away) after
each pass the main trick is they run a planer blade over the surface
Between each pass to create an exact thickness for each layer... they
were selling rebuilt Modelmaker I units for about $2000 last
winter... might be worth contacting them to see if they had any
left...

[They laughed when I asked about that- these things go for $40k used, and
$56K new. Too bad- I was seriously tempted. They do seem to get some pretty
good surface detail, if the photos on their site are to be believed. I'm
sending off for an actual sample. ]


the other Desktop unit (other than the huge laminated Laser cut paper
units and smaller Laser Liquid units that I think would be way out of
sight for a HSM to try to build) that I saw on demo was this one (and
it cost twice as much as the Sanders unit and did not seem much
better (I think it could a larger model) but this was a few years
ago)
http://www.stratasys.com/genisys.html

There is also another 3D printer-like method out there, developed by
people From MIT (I *think*).
It uses essentially a bubble jet head to shoot binder into a polymer
powder (or some polymer-ceramic) mix. The binder creates a green form
in the powder bed which can then be baked and post-processed like any
normal powder part. but I can't recall the name or find a URL for
it...

[This sounds like the z-corp product. I have seen the output from this, and
it looked pretty good. Models it generates are generally dipped in wax or
resin to harden them up and fill in surface porosity.]

and of course there are sintered metal units developed by Sandia
labs... but I think it will be cold day in hell before we see that
tech in a home shop!
http://mfgshop.sandia.gov/1400_ext/1400_ext_RapidPrototype.htm
Note that that this link does not mention the Sintered laser with
Metal dust method I could not find the link for that one... perhaps
it's now a commercial product? the link does have a nice overview of
the different mainstream types of rapid prototyping though

[Another thing I was thinking about maybe building was the sintered
thermoplastic type of RP machine, (SLS, or Selective Laser Sintering) which
work by melting plastic particles together with a laser. Mechanically, they
aren't that much more complicated than a gantry mill, and the laser doesn't
have to be as powerful as the metal-melting type. What is required is a way
of laying down successive layers of polymer powder evenly, but that doesn't
seem that difficult, really.]

>From: Don Hughes <pencad@...>
>
>Now, if we wanted to let homebrewing projects really get sophisticated,
>building an STL machine would be it. That is one project that I would
>definitely be involved in. A couple of years back I did some CAD work
>for a film studio that used STL to make the props. It really wouldn't be
>too hard to do, but the expense would be in the laser to solidify the
>STL liquid medium.

Randolph Lee boss@...
---------------------------------------------------------
Windshadow Engineering Nantucket Island, MA USA

[A lot of the complexity of STL systems is the supports that must be
provided to keep not-yet-attached parts from floating around in the goo.
The powder-based systems don't need these, since the powder supports the
detached parts in place.]

Andrew Werby
---------------------------------------------------------

Andrew Werby - United Artworks
Sculpture, Jewelry, and Other Art Stuff
http://unitedartworks.com