Ron,
I'll add a bit to Larry's message. Silicone molds may work for some ceramic
casting systems, but there can be alot of gotchas. Most ceramic
manufacturers have their own proprietary mixes for casting, but they usually
have many components in order to control the setting and shrinkage. Expect
20-30% sintering shrinkage in cast ceramics. The success would also depend
on the part design (ie. thickness, detail and required tolerances). The
ceramic mixture would typically be dense, and an RTV mold could be distorted
easily on filling if it were not stiff enough.
Another variable would be whether a "pottery-type" ceramic or a higher
performance technical ceramic material is required. Pottery-type ceramic
slips available in craft and hobby shops usually are cast in plaster molds
that draw out the water, and wouldn't set up in a silicone mold.
You may be interested in the work I did for my thesis at Georgia Tech on
ceramic injection molding into rapid tooling made by stereolithography.
Some of my papers and presentations can be accessed through the web page:
http://rpmi.marc.gatech.edu/~judsonb
Good Luck!
Beth Judson
************************
Elizabeth A. Judson, Ph.D.
Materials Science and Engineering
Georgia Institute of Technology
************************
----- Original Message -----
From: <lblasch@opw-fc.com>
To: <rp-ml@bart.lpt.fi>; Ron Hollis <rhollis@quickparts.com>
Sent: Monday, September 13, 1999 12:12 PM
Subject: Re: Casting Ceramics
>
> Ron,
>
> "Ceramics" is a broad term.
>
> You could go to any number of ceramics studios in your area and get a
> wide variety of materials and processes demonstrated.
>
> 1)Silicone molds are often used to produce high detail parts, but the
> sintering process causes warpage in non-uniform cross sections.
>
> 2)Plaster molds are used to produce hollow near-uniform wall parts by
> slip casting liquid clay mixtures into them and pouring out the
excess
> after a time. The water soaks into the plaster at the surface and the
> clay hardens. Vases, statues, figurines, sinks, toilets...
>
> 3)Ceramic tiles are usually produced by stamping dry powder in a
metal mold
> to produce a "green" part, a glaze is then added and it is then
"fired" or
> "sintered" to produce the part. Many carbide tool inserts are made
this way
> without the glaze of course.
>
> 4)Commercial dinnerware is produced by extruding a clay mixture and
then
> spinning, stamping, molding... to create the shapes desired and then
> "sintering" or "firing" them.
>
> 5)Hand made ceramics use all of the above plus hand forming or
spinning on
> a potters wheel. Another process used is rope lay-up... roll long
strands
> of clay and build the shape desired one layer at a time (manual RP
circa
> 6000 BC).
>
> 6) In the "High Tech" arena there are processes that spin fibers into
> threads that are then matted to create insulation tiles (US Space
Shuttle
> Heat Sheild) and there are even more exotic manufacturing processes
that
> produce a wide variety of application specific parts, but for your
basic
> ceramic part it's just:
>
> Shape or Mold clay mixture, Glaze if desired, Fire or "Sinter" and
you got
> Ceramics.
>
> Larry Blasch
> Design Engineer
> OPW Fueling Components
> Cincinnati, OH 45240-5003
>
> Voice: (513) 870-3356
> Fax: (513) 874-1231
> e-mail: lblasch@opw-fc.com
>
>
> ______________________________ Reply Separator
_________________________________
> Subject: Casting Ceramics
> Author: "Ron Hollis" <rhollis@quickparts.com> at internet
> Date: 9/10/99 6:01 PM
>
> Anyone with information on casting Ceramics in RTV molds?
>
> Source of materials?
> Is it a 2-part mixture for a room-temperature operation?
> Does it work with silicone?
> Gotchas?
>
> Thanks!
>
>
> -------------------------------------------------
> Ronald L. Hollis, P.E.
> Rapid Tech Engineering, Inc
> 1580 Sparkman Drive, Ste 212
> Huntsville, AL 35816
> rhollis@quickparts.com
> 256-830-8121
> 256-864-0025 (FAX)
> www.quickparts.com
>
>
> For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
>
> For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
>
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