Re: "water resistant" prototypes

From: Alexander George Cooper (agcooper@Stanford.EDU)
Date: Tue Sep 19 2000 - 02:24:30 EEST


We have been working on several layered manufacturing processes at Stanford
University that may be of interest to you. This work was started in the early
1990s at Carnegie Mellon University and after Prof. Fritz Prinz moved to Stanford
a lot of the development was done jointly between the two universities.

The goal of this research was to develop an RP method that could be used to build
functional structural parts from metals, ceramics and polymers. The original
process was called Shape Deposition Manufacturing (SDM) and focused on the
direct fabrication of metal and polymer parts. One of the projects was to build
wearable computers that consisted of electronics encased in polymer housings that
were environment resistant, including being waterproof. Several prototypes were
built and I believe were found to work. Metal parts were made using a plasma
torch, and later a laser, to deposit material in a similar fashion to the LENS
process. Applications included the fabrication of tooling with conformal cooling
passages and at least one tool was made for testing.

More recently a variation of SDM, called Mold SDM, was developed for the
fabrication of structural ceramic components. The principal application was for
gas turbine engine components. Mold SDM uses SDM techniques to build fugitive
molds which can then be used to cast a variety of part materials. Ceramic parts
are made by gelcasting and polymer parts can also be made using many castable
polymers. We are also working on using this process to make metal parts using
metal gelcasting. One advantage of Mold SDM is that since the final part is cast
in one step, there will be no layer boundaries in the part and so delamination
can't occur.

Mold SDM has been used to build a variety of ceramic components for use in
miniature gas turbine engines as well as a wide range of polymer parts including
some silicone artery models for use in flow experiments.

There is also some work being done on miniature flap type devices to control
the aerodynamics of flying vehicles. This involves the fabrication of small flaps
with built in actuators.

It seems that many of the applications we have looked at have involved parts that
interact with fluids.

For more information you can look at the web pages of the Rapid Prototyping Lab
at Stanford University ( and the Shape Deposition Manufacturing
Lab at Carnegie Mellon University (

Alexander Cooper

For more information about the rp-ml, see

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