Maker School: a CNC router isn't just a big laser cutter!

Though both a CNC router and a laser cutter can cut things out of sheet goods, the physics and mechanics of the way they cut is quite different. Let's explore how these differences effect our decisions on getting things made:

• Cutting resistance: This is an easy one...a laser cutter doesn't have any, a CNC tool does.  Imagine pushing a hand router through a piece of wood. If you move it slowly there isn't much resistence and it's pretty effortless, but as you try to speed it up you'll notice two things...it gets harder to push and harder to keep in a straight line. It's the same with a CNC tool...the faster it moves, the harder a time it will have. Though the typical CNC tool can move the length of its table in 5 secs, it may take 15 or more to make a cut that long.



• The other side-effect of this cutting resistance is that the piece that you're cutting may tend to "kick" sideways when the cut is finished and it's finally free. There are several cutting techniques that can lessen this like leaving small tabs of material holding the parts or cutting in a long plunging ramp so that the cutting force is minimal at the end of the cut,



• Another big difference between laser cutting and cutting with a bit is that the laser's cut line or "kerf" is functionally nothing and you don't really need to leave space for the "cut" between parts. With a CNC router, as with most other cutting tools, the cut has width and needs to be considered when laying out the parts or everything will be too small. Some Fabbers can cut with a bit as small as 1/16", but only with thin materials and as a very slow cutting speed. Generally the minimum bit size for most Fabbers is 1/4", and many consider 3/8" to be the "sweet spot" for cut quality and cutting speed.