Materials for large scale rapid prototyping application

Good day everyone,
For a while I have been kicking around an idea on how to do large
scale rapid prototyping without getting very far.
By large scale I mean human sized and up.
I poked around on the web looking at stereo lithography systems, but
they are quite expensive and seem quite limited in the scale of the
objects that they can produce.
One approach that I have considered is to use a CNC system to cut each
"slice" of the model out of a sheet material and appropriately glue
the cutouts one on top of another, building the shape from the ground
I'd like to ask the group what your thoughts might be for a suitable
material for the cutouts.
Polystyrene foam would seem to be the commonest, easiest available
material, but I wonder about the resolution with the beads making up
the foam, and if there would be hassles with the cutting ( toxic
fumes) and waste.
Does anyone know of any alternative materials that would have a very
fine grain and maybe superiour strength?
Off on a different tangent, I was also thinking of a version of the
lithography process, where by instead of using the laser to solidify
each layer out of a tank of resin, have a nozzle on the end of a
robotic arm, which ejects a photosetting resin paste into the
interesection of a couple of laser beams.
Excess paste can be simply removed with a flow of a suitable solvent,
and with some controls on the focus of the laser beams, quite high
resolution should be attainable.
The problem with this is, does such a resin exist, or how might one go
about producing such a thing?
Walter Minne
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An advantage of polystyrene foam is you can cut it with a hot wire. The machine which does the cutting could be very fast and cheap. Maybe adapt a phonograph turntable by adding a one-axis stepper-controlled stage to hold the cutter. You could have a very lightweight machine, even for large diameters.
Once you have the ability to make arbitrary foam objects, you can use them as cores for making harder objects. You could use them as cores for sand molds for cast iron. You could coat them with ceramic slurry and fire them. You could coat them with spray metal.
An alternative to polystyrene foam would be wax. An advantage for wax is you can remelt your scraps and use them again.
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Mark Thorson
I might visit a hardware/lumber store and look at the rigid foam insulation panels that are available in different thicknesses.
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