From: Charles Overy (cwho@lgmmodel.com)
Date: Mon Jan 13 2003 - 18:22:19 EET
Michael,
We spray our plaster 406 models with Liquitex Matte Varnish. Two wet
coats, thinned and sprayed with a cheap Badger external mix air brush. It
is not terribly strong but also better than some. We pre bake the model and
also cure between coats at about 180 degrees for no more than 30 min. It
adds enough strength for average use of an architectural model. I am not
sure I would try it on starch. For us it is the best cost/benefit we have
found. We still use CA for models that will get seriously handled.
Would anyone be intereted in a Z corp, unmoderated list? I will set it up
on our server if anyone is interested. Perhaps the user group or Z corp
also would. I know Z corp has a users forum but I don't find myself going
there that much.
Charles.
-----Original Message-----
From: owner-rp-ml@rapid.lpt.fi [mailto:owner-rp-ml@rapid.lpt.fi]On Behalf
Of admin
Sent: Thursday, January 09, 2003 9:21 AM
To: Rapid Prototyping Electronic Mailing List; kirk
Cc: peter voci; robert michael smith
Subject: Re: Zcorp users...
Hi Kirk,
Thanks for this post.
We run a machine in a small animation/digital sculpture lab at our school,
NYIT in New York. I agree the costs are eating us alive too.
I've tried a few things. I've run plaster through it to no avail. I've
strained and reused binder, which can give a rough part. I've wanted to try
something with flour and plaster mixed. I've tasted the powder and it seems
to have a floury taste. Who knows?
I also find post processing to be problematic. I've experimented the most
in this area. Gorilla Glue, unthinned, can be applied like the
cyanacrolate. You can also thin it with Xylene (but its "whew" obnoxious--
poisinous-- use all the precautions). Another drawback is that in the corn
starch material the glue will rip the surface. It contracts while drying,
leaving cracks in the part. They are sometimes large
Pure shellac works nicely but I don't use it. Firstly it doesn't have a
super strong bond. Shellac dissolves in denatured alcohol and so isn't as
obnoxious, though its still smelly. The main problem is that alcohol seems
to lessen the bond between materials while it's hardening. Parts have to be
supported somehow. I got this tip from a kindly person on this list!!
I've used all of the above solutions with a pressure pot (paint pot) at
about 30lbs psi which works nicely because it drives the material into the
part. Its all a lot of work no matter how you slice it. I dream of finding a
simple, cheap, non toxic solution.
After post processing and cost, my biggest problem with the parts are how
much they break while handling. I guess my sculptures could be reengineered
to maximize the qualities of the machine. But that was the interest in RP to
begin with-- parts without compromise to the process they are being made
with. Cantilevers are always problematic as are tiny features like toes.
(I've often said... "If I have to glue another g@# D#%^* toe on I'm gonna
scream.")
Anyway, I'd love to keep informed of anything that you do. And I'll do the
same.
Best,
michael rees
----- Original Message -----
From: kirk
To: Rapid Prototyping Electronic Mailing List
Sent: Wednesday, January 08, 2003 5:11 PM
Subject: Re: Zcorp users...
Hi rapid prototypers,
Have any of you Zcorp machine users, come up with a substitute for
Zcorp's plaster-based powder. At $500 for 15 pounds of the stuff it is
eating us alive. Our students here at UCLA Architecture are using our
new/used Z402, 24 hours a day.
Our UCLA Bio Medical Department also has a machine and they are using
ordinary granulated sugar with great success but we would prefer to use
plaster of Paris or something, here in architecture, if we can.
Here is the scoop on the sugar if you are interested. Our biomed
students are using ordinary granulated sugar (the large bags) from Costco.
Powdered sugar is too fine and doesn't work. The granulated is a little
coarse so they run it in an ordinary blender and shake it through a sieve.
They run plain water or ink on it. The print head in a Zcorp Z402 is an
ordinary Cannon unit that takes standard cartridges from Office Depot. ($35
instead of Zcorp's $65) Sometimes they simply run the black ink that comes
in the cartridge. It makes great looking black parts. Their parts look and
feel the same as our plaster parts but their machine must be kept immaculate
or it will gum up.
Their use for these parts is really incredible. When a person has lost a
part of a bone or cartilage they digitize the cavity and model a piece to
fit. They then take T cells from the patient's marrow, etc., and incubate
them on the sugar part. The sugar part has a porous lattice, so the cells
permeate the entire thing. After incubation, they wash out the sugar and
have a beautiful bone piece to implant.
z Kirk
Kirk Alcond, UCLA Architecture, Shop Supervisor,
Phone: 310-825-1626
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