From: Alair Emory (email@example.com)
Date: Fri Nov 01 2002 - 21:58:48 EET
> Seriously though, I would love to hear more people's input on the FDM's
> capabilities and speed. (or lack there of)
> Scott Tilton
For large parts with thick volumes we apply a technique called "string and
fill" to speed up the "slow" FDM machines.
We usually build two or more contours for the outside surface then override
(via UNIX scripts) the feed and speed parameters of the raster build so we
can have large air gaps (0.50" or larger). This allows the extruded ABS to
string between the outside contours and occupy a small portion of the the
thick sections. It's like stringing a cable across two mountain peaks. If
you alter the head speed you can actually tightened the extruded filament
right before you get to the other side so it does not sag. Once completed,
we apply a thin RTV rubber coating to seal the part and then vacuum inject
urethane to fill the internal volume.
Depending on geometry, a typical solid part that takes between 50 to 70
hours to build can be reduced to about 17 to 20 hours. Speed wise, it is no
wear close to our Z-Corp machine, but when you need a thick strong parts, it
works pretty good.
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