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Sintra® color choices
In many cases, you can easily accomodate your
aesthetic desires by just buying pre-colored
Sintra® (the color is uniform through the
thickness of the material). If your creation will
spend much time outdoors or under bright lights,
however, you're probably best off sticking with
white material. Colored Sintra® is not UV
stable -- the colors will fade over time, and the
material itself will get brittle. Contrast this to
white Sintra®, which is relatively resistant to
UV light; I've read that it will last 2-4 years
outdoors. You should also consider sticking to
white material (or at least light colors), if your
'bot will be involved in BEAM
competition under Halogen lights. Due to
Sintra®'s low softening temperature, your 'bot
will warp fairly readily if lights are sufficiently
near and / or bright.
Marking on Sintra®
You'll eventualy scribble on your material, if not
as part of your 'bot's final look, at least while
you're laying out lines to cut along. I've found in
my tinkering that "permanent" markers work very
well with Sintra®; pencils mark the material
reasonably well (well enough for layout work);
water-based markers are a complete waste of your
time (water-based ink "beads" on the material). I
wouldn't recommend attempting any sort of iron-on
transfer (Sintra® softens at 150° F, while
copier / printer toner won't generally melt below
about 250° F). Adhesive stickers and tape seem
to stick well to the material.
Painting Sintra®
For the most part, Sintra® takes paint
well, with no primer being required. As for
chemical compatibility, Sintra will tolerate the
majority of paints well. In particular, I have
tested out Sintra® with discount store spray
enamel, and they get along just fine.
Edge treatment
If you're going to paint Sintra®, how you
handle the edges can be a bit problematic (since
they're porous). You'll need to do a bit of extra
work on the edges of Sintra® if you want them
to look as smooth as the face sheets after
painting. I tried a number of edge treatments,
following up with a quick coat of spray paint.
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Top: painted Sintra® edges; from
left, untreated, 2 coats of paint (sanded
between coats with 220 grit sandpaper),
white glue, cyanoacrylate, PVC pipe
cleaner.
Bottom: painted Sintra® face
sheet
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As you can see, if you're going to paint
Sintra®, doing nothing to the edges leaves them
looking a bit rough compared to the faces. The best
match is yielded by giving the edges a quick wipe
with PVC pipe cleaner (although this needs to be
done with some care, as this cleaner can scar the
face sheets if you get too much on them). A simpler
approach is to just apply two coats of paint, with
a bit of sanding between them. A thin coat of
cyanoacrylate or even white glue, followed by a
quick sanding with 220 grit sandpaper can also be
used as a quick sealant, if you prefer a glossier
looking edge.
Conclusions
Sintra® is an affordable and promising
BEAMbot
building material, so long as you know and work
within its limitations. It's easy to cut, easily
shaped, fairly stiff for its weight, and is
compatible with a number of adhesives and most
commercially available paints.
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For more
information
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A very good source of detailed information
on Sintra® is the official manual,
which I've downloaded (in PDF format) from
Alusuise's
web site and mirrored here.
As for web sites on Sintra®, the
most informative one that I've found is
Sintra®
Online. It has tables of load
capacities, material properties, etc. The
site itself is written in Spanish, but the
technical information tables are all in
English. If you'd like to peruse the
Spanish material, but can't read the
language, just remember to use the
fish...
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Legalities
