CNC stands for Computer Numeric Control. Equipment
such as mills, lathes, drills, grinders, high pressure water
jets, plasma cutters, routers (also referred to as rotary
engravers), and laser engravers fall under this category. The
tips and hints I will offer in this article can be adapted to
any of the equipment previously mentioned. However, it is
mostly intended for laser engravers or — like I will
interchangeably call them — laser cutters.
Advantages and Disadvantages
A CNC laser is probably the most powerful tool I have
ever operated. I am not talking about the power intrinsic to
the amplified light which, in my case, is in the order of a
mere 25W (1/4 of what my room lightbulb consumes). I
am talking about the ability you acquire as a builder when
operating one of these amazing power horses. I like to
divide advantages into three categories:
1. Accuracy: Any CNC equipment enjoys the advantage
of a computer controlling a set of actuators to get
the desired job done. It is no secret that computer-controlled equipment can be considerably steadier
than the human hand. As a result, you will see
improved detail on laser cut parts than similar jobs
done with a typical scroll saw.
2. Repeatability. So, you built your first robot.
Awesome! How about building a second unit?
Clearly, it can be done with hand-based tools, but
CNC equipment gives you the opportunity of
repeating the same process with the press of a
button! Forget about setting up your saw, drill,
lathe, and mill for how many times you’ll need it.
With a CNC laser, it is a matter of loading up the
project file, placing the piece of material to cut
inside of the laser equipment, and WOOSH! There it
goes. In the same fashion, you could build hundreds
(or even thousands!) of robots and every time all
you have to do is press the same button.
3. Easy: Using a CNC laser cannot be any easier. All
you do is draw in the same vector fashion as you
have drawn before with software packages like Corel
Draw, Adobe Illustrator, or AutoCAD, and then print
as with any other inkjet or laser printer. Although
there are some parameters that need to be adjusted
(if you are the laser operator), these are trivial when
compared to parameter setup such as spindle
speeds, blade materials, or the use of jigs and
fixtures, etc. Like I said before: Load a file, place
some material on the laser, and press go!
It all sounds like a pure breeze and no problems at all.
Well, I would be dishonest if I were to tell you that there
are only advantages and no disadvantages. There are some
issues related with this technology, and we must overcome
them as best we can.
CNC lasers are bulky and expensive. It would be
awesome if everybody could afford one, but unfortunately
that is not the case. A good CNC laser (plus all the other
accessories such as air compressors and fume exhaust) will
cost something in between $10K and $15K. Hence, mostly
businesses tend to afford this kind of technology.
Fortunately, there is a good deal of people out there trying
to get their laser to pay for itself. They will gladly take your
file and laser the artwork for a not-so-large fee.
Parts can only be 2D. With a CNC milling machine,
three actuators move the cutting tool in the X, Y, and Z
axis. With a CNC laser, however, the cutting takes place on
the X and Y axis alone. There are ways to control the depth
of the cut by modulating laser beam power, but the
controllability of this depth is very poor as it depends on
speed and material. Some CNC laser vendors will claim the
tool to be 2.5D. I, on the other hand, look at the tool as a
2D tool and work around that. For example, you can always
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