What is a CNC machine and what does it do?

A CNC machine is usually something of a frame work that moves a cutting tool around 3 axis controlled by a computer. Its movement is very accurate, even hobby machines can move to .1mm or even better. Moving a cutting tool around to such fine, precise and repeatable movements makes it into a very special tool capable of results and accuracies that were previously unattainable at home.

While a 3D printer can make plastic structures by building layers of plastic, a CNC machine takes a piece of material, usually wood plastic or metal, and the cutting tool takes the material away almost layer by layer to achieve its results.

The side to side movement is known as the X axis and the front to back movement is known as the Y axis. The up and down movement is the Z axis. All of this movement is controlled by stepper motors that are controlled by a computer running specific CNC control software. This software controls the CNC machines movement and runs G CODE.

You can make your design and save it as an SVG file. You can then import your SVG file into a CAM G CODE generator where you can specify what each particular shape or line is, such as a cut inside or outside of a line or shape, the depth of the cut and various other options. This G CODE file is then loaded into the CNC control software. You then run it and it will move the router around the material producing whatever it is that you designed.

What can a CNC machine do?

I started building a CNC router about a week after I realised they existed.

Yes you did read that correctly, it was only in January 2020 that I discovered these machines and the fact that hobbyists were building them. I was looking at laser cutters and engravers at the time on YouTube and they just popped up down the side bar.

The first thing that appeared was a CNC engraver and I thought that I could use it to engrave on aluminium and plastic. Hopefully for text and to accurately mark where to cut and drill. The next YouTube video was a similar machine but with a router on it instead a small spindle. This could actually cut and make holes.

I realised this could open up the possibilities of making front panels and cases with the CNC machine doing the all the drilling and cutting and being able to reproduce it automatically and far more accurately than I ever could.

I then saw people using the same basic system as a plotter by replacing the tool with a pen. I then realised you could use that to check the design. Do a design and run the CNC program with a pen and paper to check it was all correct before you wasted any aluminium or plastic.

A CNC machine with a pen on it becomes a plotter and the huge advantages plotters have over printers is that they can “plot” on almost any material and not only the paper and card that will fit through a printer.

Using fabric pens on your CNC machine and you can “draw” pictures and text onto material and even clothes.

With even a small hobbyist machine the “spindles” have the power to cut through wood, plastic and soft metals. You can cut to depths as deep as the cutting bit will allow as they can just cut a millimetre at a time but repeat the cut going deeper each time.

CNC laser cutters

It’s possible to buy lasers that cut through various materials. There are specific laser CNC machines available to hobbyists that will even cut through thin metals. These machines are more complex than the machines that can be made at home as they have to have safety interlocks and safety cut outs because obviously a laser that can cut through metal could be potentially very dangerous. The fumes produced can also be toxic and the lasers also need to be water cooled.

I decided not to go down the road of a laser cutter and instead went for a 3018 CNC machine however the package I bought came with a low power laser (about 5 watts I think). If you are interested in buying a CNC machine as a beginner I have a more detailed article that you can read here.

Although you shouldn’t treat these lasers as toys as they can certainly do a lot of damage, they don’t need high voltage external power supplies or water cooling. They still can produce toxic fumes though depending on what you melt, especially plastic and acrylic so you should still make sure you have decent ventilation or at the very least an open window. You should also use eye protection whenever you use the laser. There’s more on that here.

What I found with the laser that it was very useful for engraving text onto black acrylic. With a bit of experimenting with focus, power and the speed of movement I was able to get decent results. One thing worth noting was that I almost gave up with it until I discovered the laser mode that you should enable in GRBL. This isn’t something that I was aware of even after lots of reading.

If you want to know more specifically about what CNC machines can make I have another article about that here.