The Contour Crafting patent: if you refer to the documents is an explaination of a fabrication process which is potentially caple of doing great jobs in RP world. There are some implementation and materials addressed in the method but not necessarily it is limited to those.
For the sharp corners think about a zero shrinkage(or determined shrinkage) photo set material, in paste form( Not so much in the imagination). For the aparatus it is already done, not such a sophisticated 5 axis CNC will work(X,Y,Z,A(rotation of the trowel),B(angle of side and top trowel)).
There is only one vertical line in the side trowel which is finishing the surface depending on the angel of the side trowel with the tangential line of the outer surface, so the aparatus can turn around the corner to keep that line in the same position for that sharp edge. Offcourse based on the size of the trowel there are some limitations for this turn.
> From firstname.lastname@example.org Wed Jun 25 13:46 PDT 1997
> Date: 25 Jun 97 16:26:50 EDT
> From: Peter Gien <email@example.com>
> To: rp-ml <firstname.lastname@example.org>
> Subject: Contour Crafting
> Sender: email@example.com
> Content-Type> : > text>
> Content-Length: 657
> Concerning the Contour Crafting patent, I would like to know how the shaping
> trowels get into sharp reentrant corners? As for building boats, I think not. I
> would much rather mount a high-speed router on the gantry and carve the mold
> without shrinkage.
> The CC technique reminds me of the laser cutting machines that cut flat
> materials with a bevel edge. The angle of the bevel varies to match the
> curvarure of the STL file. This technique is as old as the hills. The PTO should
> be staffed by people who are a little more imaginative.
> Peter H. Gien
> POGO International, Inc.
> 252 Broadway Avenue, ste 3
> Long Branch New Jersey 07740
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