How to program a CNC machine

How to program a CNC machine

CNC machines take the guesswork and human error out of cutting jobs, but they also need technical knowledge to properly utilise.

CNC machines need specific instructions in order to run, and errors can be nothing short of catastrophic for time management and wasted money.

CNC machine programming is an essential skill in many manufacturing environments and one that keeps your machine tools running on time and profitably. Let’s look closer at how to program a CNC machine.

What programming language do CNC machines use?

G-code is the most common and widely-used programming language for controlling CNC machines. G-code is unlike the programming languages used to make apps and websites; by comparison, it’s very straightforward even when controlling a complex series of actions to be taken by the CNC machine.

G-code derives its name from both the way it’s structured and its focus on geometry. Commands are preceded by the letter G and a number to instruct the machine on the nature of the command. For instance, G0 means that the machine will make its move to a specified location rapidly.

Commands are followed by coordinates along the XYZ planes that pinpoint the necessary location, so a G0 command followed by coordinates means the machine will quickly move its tool to the given location.

Furthering its simplicity, G-code is organised into ‘blocks’, which act like paragraphs to separate out the lines. Each block is concerned with an individual cutting operation.

G-code can be written out manually to build a specific program, but for the vast majority of jobs, that won’t be necessary (or even feasible). For complex parts, this could mean writing out thousands upon thousands of lines of G-code in by hand.

Now, G-code is often automatically generated by CAM (computer aided manufacture) programs, which read a three-dimensional CAD model and produce the necessary code to create that shape through machine tool movements.

Despite the ease of this, knowledge of G-code is still ideal to verify code and understand any crashes, as well as having a true understanding of your CNC machines and how they work. Understanding the functional basics of G-code helps you read back the code generated by CAM programs and ultimately control the process better.

G-code includes other pieces of code using letters and numbers to perform functions besides movement. M-codes, for instance, control actions like activating coolant and changing tools.

Which format of CNC programming is used currently?

G-code, despite being an industry-wide standard, can differ from brand to brand and between machines. This is encouraged by the fact that not every CNC machine manufacturer will create their machines alike, and one CNC machine will have different functionality and hardware from another. This means that a piece of G-code relevant to a MAZAK machine won’t necessarily mean anything for a Haas.

The file extension for many G-code files is .nc, but others such as .cnc and .gcode exist. These files cannot be converted from one format to another, but they can be read using simple text editor programs on a computer.

When dealing with 3D models that can be converted into G-code, the common format is STEP files, but others such as Solidworks and SketchUp are sometimes used.

Which software is best for CNC programming?

Just like with word processing, making spreadsheets, or creating digital art, there is no one option for CNC programming and different offerings have their differing strengths and drawbacks.

One of the most popular programs for 3D modelling and CNC programming is Fusion 360. Developed by Autodesk, this program supports the modelling and CAM side of things — which ensures that the CNC machine can follow the path laid out for it — and has an integrated G-code editor.

This arguably provides the best environment for validating a 3D model and generating the code necessary to cut it out. Fusion 360 also allows for CAM simulations, giving users another confirmation of how their code will play out once running in the machine.

There are other options available for a range of price points and with different capabilities, but as a popular all-rounder with tons of support available, Fusion 360 is an excellent choice.

CNC machining with GA Profiplast

When it comes to plastic fabrication, GA Profiplast’s team have expert knowledge of CNC machine programming and function, making us the top choice for helping you optimise your parts and get them made fast and to exact specifications.

To learn more about our plastic machining services, get in touch with us today.