Intro to 3D modeling - 3
The positional accuracy of the system is quite good, about 0.2%
or 0.002” per inch. So rather than make a master from which I
would create a mold, I decided to make a mold box that would
produce the mold directly. I asked the Shapeways technical
people if anyone had ever done this and the answer was “No,
never.” It would be an inexpensive experiment so I went ahead
and gave it a try.
Overall, it worked pretty well, but there a couple of things to
watch. First, contrary to advertising claims, the surface is not
smooth. It feels smooth, but there are little grooves between
the rows of deposited plastic. Silicone rubber won’t stick to the
plastic, but it gets trapped in these grooves and is very difficult
to remove. I broke part
of the mold box prying
the RTV silicon from the
bottom of the box. The
surface finish on parts
from this mold made
them essentially useless.
Things couldn’t get any
worse so I applied a coat
of gloss finish to the mold
to fill these grooves, and
the second attempt at
making a silicone mold
worked well. Two coats of
gloss finish would prob-
ably be better, but you
have to be careful not to
obliterate the detail.
4
4. The door, painted and
assembled.
MRH-Aug 2014
