ENV Laser Primer
Our CO2 laser operates in three distinct modes:
Etching: Where the laser beam rasters, traversing left and right as it slowly steps
vertically through the entire image area.
Scribing: where the laser beam follows the direct path of a vector graphic.
Cutting: where the laser beam follows the direct path of a vector graphic with
enough power to cut completely through the material.
Color determines the mode of laser operation.
Shades of black, including grays or grayscale objects will be etched.
Blue colored objects set to a hairline thickness (0.000 or hairline) will scribe
Red colored or outlined objects set to a hairline thickness (or 0.0000) will cut.
Etching takes considerably more time than scribing or cutting as the laser will
raster the entire canvas instead of moving directly upon the vector‘s path.
Use the above color code when creating artwork. If the schemata is correctly followed,
including line weights, it is possible to laser etch, scribe, and cut from a single flattened
image. However it is highly recommended that each color occupy a separate layer in your
graphics program for ease of operation if corrections need be made. We may run the laser
directly from the following programs:
AutoCAD 2002
(hairline = 0.00)
Adobe Illustrator CS3 (hairline = 0.0001) RGB R= 255 G=0 B=0
Photoshop
Programs have variations in defining hairline; for all programs the vector line must be
Red to cut.
In Operation
Begin with a canvas size of 16” x 12” in landscape format.
All artwork must be placed within this canvas; a small amount of border, 1/4” is
reasonable.
In most graphics programs you may specify the canvas size and the artwork may then be
rendered directly upon the canvas. In CAD it is recommended that the canvas be drawn in
a separate layer other than black, blue or red, and that the 16” x 12” rectangle may be on
a layer that is not illuminated when printing, i.e. sending to the laser, as the laser will try
to etch any layer that is set to print.
The laser regards “Home” or X=0 and Y=0 as oriented in the upper left corner of the
canvas. From the Home position the machine measures in inches to the right up to 16”
and down to a maximum of 12”. In practice, if you wanted to engrave an image that was
only three inches square, the material would be placed against the top left of the laser
bed, and the laser will know to send the 3” x 3” image to that location.
If for example your material to be cut is only 8” x 8” simply orient your artwork in the
top left corner of a 16” x 12” canvas.
Etching may be done on glass, plexiglas (low polycarbonate such as acrylic) wood,
anodized aluminum, treated tile (lasertile.com), and specialized marble. Harder metals
including stainless steel may be engraved by first painting the surface with Cermark
(additional cost per square inch) whereby a black pigment is permanently bonded to the
metal. Cermark will not work on aluminum or softer metals.
The laser is capable of cutting up to 1/4” thick basswood and 3/16” baltic birch. Wood
needs to be cut in a single pass because if it is not cut through the first time, the resulting
char of carbon and resin renders the laser incapable of penetrating cleanly. ¼” plexiglas
can also be cut on the laser, acrylic is best, high polycarbonate plastic such as Lexan do
not cut well.
Vector graphics are derived from mathematical formulas and for this reason can be scaled
without difficulty. Bitmaps are not as easily scalable as their quality is determined by the
resolution they were created with. Bitmap images (digital photos) may be etched by the
laser. The laser has a resolution of 250 DPI for most materials. Some softer or more
flammable materials will produce a better image utilizing 150 DPI.
When working with a Bitmap image, the image must be converted to grayscale. The
greater the contrast the better, and an image with a lot of grey in the background will not
generate great results. Consider processing the image to show what you desire to feature,
sometimes it is best to delete the background entirely in Photoshop. It is recommended
that when importing an image that it is imported as a Tiff.
From Photoshop various Halftone Screens are applied, depending on the material being
etched. For example, in wood a frequency of 60, an angle of 45, and a square may be
applied, while acrylic will use a frequency of 90, an angle of 45 and a square.
The laser works by amplifying a very specific frequency of light and focusing it on an
extremely small focal point. For this reason it works best on flat surfaces. On a round
object the focal point will be compromised, and a distortion of the image will occur, as
artwork will become elongated about a radius. “Squishing” your artwork at the polar
extremes may compensate for the elongation effect. A rule of thumb for etching a small
dowel (pencil), for example, is that the artwork or lettering should never exceed 1/2 the
diameter of the object. Obviously there are diminishing returns on larger diameter
objects.
Due to viruses on flash drives, artwork must be e-mailed to the Model Shop in
advance: clhoke1@csupomona.edu
The cost of using the laser is $1.00 per minute.
In crunch times a sign up sheet is posted in the Model Shop.
(909-869-2677).