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Although there
are no shortcuts to achieving the transparency and brilliance of clear
parts, the process is simple and inexpensive.
With most
rapid prototyping technologies, clear models are either impossible or
too time-consuming to make. However, PolyJet Technology makes it both
possible and practical. The smooth surfaces of PolyJet models and the
translucency of FullCure® 720 model material combine to make clear
models a reality. Right out of the machine, you are ready to begin
light sanding and polishing to produce a clear prototype.
Building a 3D model
Orient the
model so that the critical surface faces upwards and build in glossy
mode (do not use support material). Wherever possible, avoid support
material on clear surfaces since it will be difficult to remove
(figure 1).
Preparing the 3D model
Using the
WaterJet station, thoroughly pressure wash the model to remove the
support material. Pay special attention to corners, channels and
pockets to ensure that the support material is completely removed
(figure 2).
Note: Sand blasting is not recommended. The
abrasiveness can create small pits that are difficult to polish.
However, for a frosted surface, mask off the part and sandblast the
unprotected area.
Dry-sand surfaces
Following
support removal, thoroughly dry the model and sand all surfaces with
200-grit sandpaper. A light sanding will remove surface imperfections
and layers.
After the 220-grit sanding, repeat with 320-grit to begin the polishing process (figure 3).
Wet-sand surfaces
Lightly wet-sand the model, progressing through 400, 600 and 1000-grit sandpapers.
The
wet-sanding is not intended to remove material. Rather, it reduces the
scratches from previous sandings, so a light touch is all that is
needed.
Between each sanding, rinse the model with water to remove any grit and debris (figure 4).
Micro-mesh sanding (optional)
For an exceptional finish, polish the model with micro-mesh sandpaper.
Sand
all surfaces with 1500 micro-mesh sandpaper. Depending on the desired
results, continue sanding with 1800, 2400, 3600 and 4000 micro-mesh
sandpaper.
As with step 4, you can use soapy water, mineral oil or vegetable oil to lubricate the surface while sanding (figure 5).
Polishing the model
The final
step to achieving a clear PolyJet part is to buff and polish the
surfaces. Using either a buffing wheel or a rotary tool with a buffing
drum, apply a polishing compound to the buffing pad and work it onto
all surfaces of the model. Reapply the polishing compound frequently.
An effective polishing compound is 3M
Plastic Polish. Polishing compounds for plastics are also available
from several other manufacturers. Some of these compounds do not
require a buffing wheel.
After polishing all surfaces, buff off the
compound with a soft cloth or a clean buffing pad. Your PolyJet model
is now ready to be used as a lens, container, or cover (figure 6).
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