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3D Fact Sheet|
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Description
Some of the most attractive signs are those which are
reverse engraved in acrylic and color filled. The effect is a
rich looking sign with colorful, sub-surface graphics that have
more dimension than surface engraved products.
One common method of reverse engraving in acrylic is to use a
cutter with a wide included angle (90°) which produces a broad,
"V" shaped groove. Due to the angle of the side of the
cut, light entering the edges of the sign reflects off the surface
of the cut, instead of passing through it, and causes the letters
to stand out.
One of the problems with this method is that due to the shape
of the cutter, the width of the cut increases significantly with
increased depth. As a result, the bases of the letters can run
together when engraving to any significant depth.
To eliminate this problem and further enhance the effect of reverse
engraved acrylic, Antares introduced the "3-D cutter."
This cutter is sharpened to a narrow included angle, which allows
for engraving at considerable depth without significantly broadening
the stroke. After the letters are filled, the resulting effect
is that the lettering appears to have been "cast" into
the acrylic plate.
Technique
The 3-D effect becomes more pronounced as both the
material thickness and the engraving depth are increased. The
best effects come from engraving to a depth of 1/2 to 3/4 of the
material thickness. As a guide, 1/8' material should be engraved
at a depth from .060" to .090" and 1/4" material
to a minimum depth of .125".
When you consider that most engraving is done to a depth of .010"
or .015' in soft materials like flexible engraving stock, engraving
deeply in a hard material such as acrylic requires more time.
Engraving to a depth of .125", for example, would require
four to five passes of about .030" depth per pass.
One problem inherent to acrylic engraving is melting of the material
due to the heat generated by the cutter. If the heat is excessive,
the chips that are not ejected by the cutter will "weld"
themselves to the walls of the cut and to the cutter itself. When
the latter condition occurs, the cutting action is severely reduced
and the melting problem is magnified.
To help minimize the problem, the initial roughing cuts should
be made at a reduced spindle speed (cutter speed) and a reduced
feed rate (engraving speed). The slower cutter speed prevents
heat build-up and the slower feed rate allows the chips to be
cleared from the cut. It is strongly recommended that the final
pass be a "clean-up pass" cut .002" to .003"
deep. This pass, done at the same engraving speed but a higher
cutter speed, will clean out any chips left in the cut and produce
a smoother finish which enhances the appearance of the paint fill.
Using a cutting fluid virtually eliminates the melting problems
and speed up the engraving process. A water-soluble fluid keeps
the heat below the melting point of the acrylic, provides lubrication
of the cutter, and can be washed off with soap and water.
If the sign is to have a background color, the plate can be spray
painted on one side before engraving. After the paint has dried
sufficiently, the plate is engraved through the painted surface
and then filled with a contrasting color. If you are not required
to match a specific color, you can eliminate the hassle of surface
painting by using a reverse engravable material such as Rowmark
Slickers.
The Slickers are a multi-layered acrylic material with a clear
face and a colored back. The engraving is done through the colored
layer and then filled with an acrylic-based paint. Since the colored
layer is very durable, the material can be engraved using a nose
cone without the worry of scratching through the surface as is
possible on painted surfaces. The Slickers are available in a
wide range of colors and in thicknesses of 1/16", 1/8",
and 1/4".
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