CNC routers are "computer numerical controlled"
machines that take the fine work of measuring, sawing, wood carving, planning,
drilling, cutting mortises and tennons, and even collecting dust out of the
hands of the carpenter and put it into the processors, planers, drill bits, and
other fiddly bits of the computer and router machine. What can be achieved in
terms of project design, time savings, and labor savings with a CNC wood router
is nothing short of stunning. But even more stunning is that these computer /
router machines are now affordable for use in the home shop.
Cutting a narrow triangle-shaped opening with power and/or hand
tools is anything but simple. Cutting parts with precise details is a task well
suited for digital woodworking and CNC Routers.
How I use a CNC Router: Part Two
In the previous post, I gave an overall explanation of the
process that I use to make furniture parts with a combination of various power
tools and hand tools. Essentially, it’s a hybrid process of power and hand
tools that many other professional and hobbyist woodworkers use. The goal is
consistency and accuracy. I mill and square up materials with jointers, planers
and saws. Then, I rough cut and final shape parts to my patterns.
Stock Preparation
So, how does the process change when
you use a CNC Router to cut out your parts? For me at least, some things are
the same. I still prepare my stock with the same tools as before with saws,
jointers and planers. Getting your boards flat and square is even more critical
when using a CNC Router. You want the boards you’re going to CNC Router very
flat. From this point on, everything changes.
Below is a simple example of the CNC Router
doing what it does well: accurate part cutting. In this example, we’re not
cutting out a complete part, just a shape in the middle of a board. A
long, thin triangle. As simple as it looks, I’ve had to make this exact cut
many times. It’s been difficult with any combination of power tools and hand
tools. The red triangle in the drawing below shows you the area I need to
remove.
A Challenging Cut for Woodworkers
Here’s the problem: The triangle is
very narrow. It’s about 2-1/2” wide at the top and tapers down over 9” to a
sharp point. It might seem simple but in practice it’s been a
difficult detail to cut out accurately. I’ve tried all the woodworking processes
that you’d expect. The most successful technique has been to drill holes in the
corners, then jig saw or scroll saw out the triangle. So far, I’ve been unhappy
with the results. Even holding a jigsaw to a guide, the walls of the triangle
are not perfectly straight and smooth. So, after rough cutting, I set up a
two-step shaping process with the pattern to get the walls straight.
But, we’re just getting started. The sharp end of the triangle keeps it
challenging. Time for rasps, files and lots of sanding in a difficult-to-access
area before the job is done. After a lot of time-consuming work, I’ve never
been completely happy with the quality of the results. This job is all about
precision. That makes it a perfect task for a CNC Router.
First Draw the Part, Then Cut It
After drawing the board and the
triangle in CAD and then programming the CNC Router with CAM software to
make the cut, I place the board on the bed of the CNC Router, align it, clamp
it tightly and begin. I cut my way down in steps to the full 1” depth of the
board just as you’d do with a router. Small connecting pieces of wood at the
bottom of the cut called “tabs” or “bridges” are left to keep the triangle just
slightly attached to the main board. That keeps it from rattling around during
the last pass and potentially damaging the part.
You can see the tabs being machined in
the video below when the CNC Router pauses, rises up and then drops down.
Total time to cut the triangle opening: 116 seconds. The results are perfect.
When you add in the time for changing boards and clean up, eight boards
were completed in 20 minutes.
Sometimes
a small detail is a big challenge. Cutting this narrow triangle out of a board
is particularly difficult using other woodworking techniques. With a CNC Router it’s done quickly and accurately.
Though this triangle is only a simple
example, it should give you an idea of how accurately and quickly a CNC router
can machine parts. If we were cutting a complete part with any combination of
curves or shape, there’s a bit more involved but in general, the process is
pretty much the same.
As I said previously, a CNC Router can
do many things. Certainly, it does some tasks better than others. And, as
always, some tasks are better left to hand or power tools. Accurate part
cutting just happens to be one woodworking task a CNC Router does very
well.
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