[Arm-netbook] On (potentially not) 3D printing laptop case parts

[Neil Jansen]

On Wed, May 24, 2017 at 8:33 PM, Forest Crossman <cyrozap at gmail.com> wrote:

> I'm not sure how complicated the parts of the laptop case are, but if the
parts could be re-designed to be optimized for resin casting, it might cut
down on the production time. Of course, I've never done any resin casting
before so I don't know how feasible this would be in practice. Also, I have
no idea how fast modern 3D printers can run now, so the speed advantage
might not even exist any more.

I've got a tiny bit of experience here, for what it's worth.  For our open
source SMT pick and place machines, we used 3D printed molds for
mass-producing a particular part on the machine.  They were cast in medium
to low durometer urethane, but the process is somewhat similar to other
types of resins.

The main problem we had were that the molds took a while to clean.  The
material oozed out of the top in a few strategically placed holes.  Those
would clog constantly and required a lot of labor to clean, however,
probably still MUCH less than if the parts were 3d printed.  So it was
slightly annoying, but less annoying and quicker than 3D printing that
particular part.  There are prototyping shops in China that can do this in
limited runs, with great results.  No idea about cost though.

The surface finish was actually quite nice.  It was basically an inverse of
the 3D printed part.  It looked 3D printed, but under magnification, you
could see that the the ridges were backwards.  If the master parts were 3d
printed via an SLA process, then those lines would disappear, and the
accuracies would be much better.  We usually got very small air bubbles on
the surface of the part, but it was casted upside down so they were never
seen.

Probably the main detractor for resin casting in this particular case is
going to be how the parts are designed.  Unless a part was designed to be
cast, it's probably not going to be cast.  lkcl has already spoken that he
did not want to redesign any of the parts if he could help it.  For that
reason alone, I'd guess that it's probably off the table.

I'm definitely not an expert though, this is not really my area.  Just
figured I'd share my brief experience.
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