Creating CNC Textures
By Randy Johnson
CNC routers are opening up lots of new ways to create
textures in wood. Here are my three favorite ways
of creating textures using a CNC. Th e fi rst method uses
the repetition of shapes to create a design that is routed
using one or more bits. If you enjoy doodling patterns,
this is a technique that you will enjoy. Th e second
method uses programming built in to the design soft -
ware to generate a texture design that simulates a handcarved
pattern. Th e third texturing method starts with
a photograph and converts the light and dark areas into
the routing paths. Each method has a few basic rules to
follow, but add some imagination and the variations you
can achieve are virtually limitless. I used Vectric Aspire
CNC design soft ware to create the textures for this article,
but other soft ware packages such as ArtCAM and
EnRoute can also be used to create textures.
Shape-based textures are created by repeating
a pattern of either asymmetrical or symmetrical
shapes. Patterns can be hand-drawn or drafted with
a CAD program such as Google SketchUp. Hand
drawn designs need to be scanned or digitally
photographed so they can be imported into the
CNC design program. CNC design programs are
also capable of creating shape-based patterns. One
creative aspect of this type of texturing is that you
can rout on the lines or between them to achieve
different effects. I routed the crackle texture shown
below using a 1/4" dia. 60° v-bit. It took about 60
minutes to carve the design into this 10" cherry lid.
The dome shape of the lid was created first using a
1/4" dia. ball nose bit.
Click any image to view a larger version.
Using the built-in texturing program that comes with most CNC
design software packages is an easy way to create a simulated
hand-carved texture. As shown in the program window to the left,
there are several options to choose from when designing this type
of texture. Adjusting these variables enables you to create a wide
variety of simulated hand-carved textures, ranging from those with
long, closely spaced cuts, to those with short, widely spaced cuts—
and anything in between. Once the options are selected, the
program creates a semi-random pattern of lines (see middle image
below) for the router bit to follow. I used the settings shown here to
create texture on the walnut lid show below. I used a 1/4" ball nose
bit to create the texture, but other profiles such as straight bits or
v-bits can also be used, expanding your options even further. It
took about 60 minutes to carve the texture shown below.
Another way to create a CNC texture is to start with a photo.
Not all photos work equally well, however. That’s because
the CNC design software reads the light areas as high points
and the dark areas as low points and tells the CNC router to
carve accordingly. A good photo image is one that is evenly
lit without long shadows, but yet has good contrast. As you
can see in the alligator skin photograph below, the highlights
accent similar areas, while the dark areas are consistent in
the rest of the photo. This type of photo will create a texture
that closely resembles the contours of the original. Carving a
photo-based texture requires the use of a small ball nose bit to
attain the details. For the design below, I first roughed out the
texture and dome shape of the lid with a 1/4" ball nose bit and
then carved the final shape and details using a 1/8" ball nose
bit. It took about two hours to do the final routing and about
the same amount of time for the roughing passes.
Shape-based textures can take many forms, from low relief
to high relief, and from subtle to bold. The three textures
above are just a sampling of options that are possible with this
approach to designing textures for the CNC. The one on the left
was created using a collection of small circles that were then
routed around with a 60° v-bit. The middle design is simply an
array of concentric squares, while the one on the right uses a
grid pattern made with a 120° v-bit.
Software-based textures are the easiest—and often
the fastest—to create, and can be run on top of a shape
(left), around a shape (middle), or overlapping in different
directions (right). These options allow you to be selective
and creative in where and how the texture is applied.
Using different bits will also expand the variations you
can create with this method of texturing.
Photo-based textures are an easy way to simulate existing
textures—as seen in these three examples. The weathered
end grain (left) shows a surprising amount of detail, as
does the cloth texture (right). The stones (middle) create
an interesting pattern, although they are rendered quite
flat. Additional depth can be added to the stones through
the use of other modeling tools, if so desired. The thing to
remember about creating textures from photos is to
always start with a photo that has even contrast.
This story originally appeared in American Woodworker April/May 2012, issue #159.