Re: Applications

From: Michael Brindley
To: Ian Gibson (University of Hong Kong)
Cc: RP-ML
Date: Sunday, March 19, 1995
Subject: Re: Applications 
Ian Gibson wrote:
> Secondly, when are we going to stop thinking in layers? We design 
> ...
> blades. When are we going to see an RP system that builds in the same way? 

I haven't priced a five or six axis general purpose robotic system,
but I can say that it is going to be much more expensive than a 
simple x-y-z system.  I imagine that galvanometer mirror systems
(a la 3D Systems) are less expensive than than a precision x-y table
covering the same area.  Sander's system was selling for about
$70 000 (USD) last summer using an x-y-z gantry system.  I believe
Statasys and Helisys have mechanically similar systems for similar
prices.  Then there is the problem of accuracy.  Each seperate joint
adds slop.  Then comes the problem of the software to control and
direct the building process - much more difficult than the flat
(planar) layers currently popular.  Until we are able to assemble
at the molecular level (e.g., Star Trek's replicators/transporters),
I have difficulty imagining a building method which does not involve
sequentially adding material on a 'macro' scale (for an additive
process of course). 

If the differention between layers goes away (making a truly monolithic
structure), does it matter that it was originally created by adding
material in some kind of layer?  A five or six axis machine could
build 'croissants' - the layers are 'parallel' but follow the curve
of the exterior surface.

Master's original patent on droplet deposition included a number of
ideas on how to build omnidirectionally.  One interesting idea was
to fire 2 droplets from 2 seperate 'nozzles'.  When the droplets
hit, they would stop and solidify.  The precisions required for such
a process make it currently impractical.  If anyone can prove me
wrong, please do!

Another person was working on a system which had a vat of liquid
photopolymer and two lasers.  The spot in 3-dimensional space
where the lasers beams intersected inside the vat would solidfy
(but not the polymer along the individual laser beams paths).  I
believe this was significantly before the work leading to 3D 
Systems, Inc.  To the best of my knowledge, this system was never
commercial.

  --> Mike Brindley   brindley@ece.orst.edu