MASTER® Dyna-Cast
is a two-part (1:1) quick-setting urethane that, because
of its special characteristics, can be formed into
a skin or shell over a master pattern or core stick.
This application of Dyna-Cast quickly and easily creates
inexpensive, close-tolerance molds for pattern duplicating
or temporary coreboxes.
Dyna-Cast is an ideal material
for this use because of its longer pot life (approximately
5 minutes). Unlike other "quick-setting" plastics,
it does not transform from a liquid to a solid in
just a few minutes. The setting process goes through
an 8 to 10 minute gel cycle where it can be brushed,
troweled, or scraped onto vertical sidewalls. The
adaptation of these techniques is easily developed.
In one or two attempts, a technician can become an
expert.
The following explanation should
address the majority of applications...Your job may
vary, but the techniques are the same. Size of the
work is of little consequence, as the larger the job,
the more practical this procedure becomes.
As in any molding process, develop
a parting line or affix pattern to a flat plate.
Prepare pattern with correct release
agents. |
Initially, mix just
enough Dyna-Cast (1:1 ratio) to cover the master pattern
as you would with paint. Then, while the plastic is
in its most liquid form (first five minutes), pour
it over the entire surface and, while it is still liquid,
use a brush to cover the entire surface. Note: The
liquid plastic will puddle in the low areas.
As the liquid begins to thicken
(in the next 8 to 10 minutes), using a brush, drag
the puddled material back up on the high spots. Concentrate
on covering outside radii and sharp corners. When
covering outside corners, drag plastic up the vertical
wall and allow to drape over corner. Do not allow
brush to touch corner. When the Dyna-Cast becomes
too thick to work, stop and IMMEDIATELY mix a second
batch. Allow the new mix to thicken slightly in the
cup or on the job, and again concentrate on the hard-to-cover
areas. When the second coat becomes too thick to
work, set in any ribs, and work as before.
Mix a third batch, tie in the
ribs, and work as before.
With three applications,
the surface thickness should be 3/16" (minimum) and
thicker in the low areas. The entire procedure should
take less than 30 minutes. Allow two hours form the
initial pour before demolding.
NOTE: Mandatory and recommended
industrial hygiene and safety procedures should always
be used when handling materials.
|
