An RP-ML subscriber wrote:
> hi,
> Can you please tell me what you mean by 'green-body fabrication'
Dear RP-World,
I apologize for using jargon in the list without explaining it.
A green body is the thing that is used in a "sintering" process to
get a
solid ceramic or metal object from an initial powder. The common example
of
these processes is in pottery, in which clay is shaped into a pot or
other
object and then put in a kiln (furnace) to bake out the water and sinter
(a
lot like melting) the clay (a ceramic powder) into a solid mass. In
industrial
processes, a green body is made of a ceramic or metal powder with a
smaller
amount of plastic or other material that holds the powder together in a
specific shape. The green body is then put in a furnace where the
plastic is
burned away and the powder particles are fused by sintering just as in
the
case of the pottery example.
It is called a green body by analogy to lumber, which is called
"green"
before it is treated in a furnace to get rid of internal moisture.
What is exciting today is the ability to use a fabricator to make
the
green body. Previously, green bodies had to be made by molding, which
requires
tooling, which is very expensive. A fabricator allows you to make a
small
number of green bodies economically, making prototype and low-volume
production economical like never before.
Best Regards,
Marshall Burns
marshall@ennex.com
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-------------------------------------- Original message:
From: marshall@ennex.com on 11/11/97 21:21:14
To: malmberg@malmbergeng.com
cc: matt_murphy@peragroup.com, rp-ml@bart.lpt.fi (bcc: Rapid
Prototyping/Daewoo)
Subject: Green-body fabrication technique comparison
Guy Allen Brady wrote:
> Well, now, this is a nice surprise. I've been working on
> Stereolithography of Ceramics for the past 2+ years. My suspensions are
> 50vol% Alumina in a photocurable resin. There are two others groups (at
Dear Allen and others,
I wonder if I might ask a question that could spark some
interesting
technical debate.
What are the relative pros and cons of the various techniques for
fabricating green bodies of either ceramics or metals? The techniques
that
must be considered include direct fabrication of the green body:
- Selective photocuring of a photopolymer/powder suspension
(SLA)
- Laser sintering of polymer-coated powders (SLS),
- Extrusion of a polymer/powder paste (FDM),
- Lamination of polymer/powder tapes (LOM),
- and perhaps some other direct techniques.
And one should also include indirect techniques of:
- Fabricating a mold or master which is used to mold a powder
system
(old fashioned P/M as well as Keltool, etc.).
What do people think about how these various techniques campare?
Best Regards,
Marshall Burns
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