What is CNC?

Above: Maker Ensamblería in Mexixo City works on the Valoví Chair

What is CNC?

A CNC machine is a computerised, X, Y, Z driven milling/turning router. The CNC machine is a high precision, rapid and highly repetitive manufacturing centre. It is mainly used for mass production in various industries such as: aerospace & defence, automotive, consumer goods and furniture.

How does it work?

A programmable controller receives input in G-code, the universal computing language for CNC routers. G-code drives the machine across its axis, be that 3, 4 or 5 axis routers. Not only is G-Code universally applicable to CNC routers it is the designated programming language for all X, Y, Z axis driven machines (3D printers, laser cutters, etc.). As a general rule this language consist of two major parameters coordinates (X, Y, and Z) and G commands (Also M commands, although not relevant for now). The coordinates are used as a reference to the G commands which specify what action the machine should do along the coordinates.

In other words…

Let’s say I want to drill a hole. That means I need to tell the machine where I want it to drill the hole a.k.a. the coordinates. Once I know the position of the hole I need to instruct the machine to commence a drilling operation in that position also known as G command.

So you’ve got your machine ready…

Stop the press! The coordinates need a point of origin before you press the green button. Imagine being plonked in the middle of a forest at night with a map. You have no points of reference as the light is poor so your map becomes very hard to read. Another way of imagining it is having a standard map key, “You are here”. So before any programming is done defining a zero position is the first step.

Point of origin

Above represents an example of where to place a point of origin

Okay point of origin is determined, now to CAM…

Thankfully computer-aided manufacturing (CAM) has eradicated the need for native fluency in G-code. CAM is software that creates the graphic motions which are eventually translated into G-code. There’s lots of different methods of generating your G-code and it varies from plugins, to popular CAD programs such as Rhino, to software that accompanies your CNC machine.

Once running your CAD design through the CAM plugin or accompanying CNC machine software you can run a virtual cutting simulation to check for any collisions or problems, and efficient material removal. This stage is crucial, it’s the moment when the program ticks the approve box to start cutting. This is why a prayer before starting the machine is not mandatory!

The next step

There’s lots more detail we can get into here (lets say you’ve read chapter 1) but to get started with CNC machining I recommend joining a local makerspace or tech shop where you can get training and spare yourself the upfront cost of buying a CNC machine before you are more competent!

Boris Goldberg is a Community Contributor at Opendesk. He’s based in Tel-Aviv, Israel and spends time assisting the verification process for new designs, and writing for the blog and soon to be Field Guide.

Do you have experience with designing or making and wish to contribute to the blog? Email field@opendesk.cc with your topic!