Speak To The Machine

May 21, 2023

If you own a 3D printer, CNC router, or basically anything else that makes coordinated movements with a bunch of stepper motors, chances are good that it speaks G-code. Do you?

If you were a CNC machinist back in the 1980's, chances are very good that you’d be fluent in the language, and maybe even a couple different machines’ specialized dialects. But higher level abstractions pretty quickly took over the CAM landscape, and knowing how to navigate GUIs and do CAD became more relevant than knowing how to move the machine around by typing.

Strangely enough, I learned G-code in 2010, as the RepRap Darwin that my hackerspace needed some human wranglers. If you want to print out a 3D design today, you have a wealth of convenient slicers that’ll turn abstract geometry into G-code, but back in the day, all we had was a mess of Python scripts. Given the state of things, it was worth learning a little G-code, because even if you just wanted to print something out, it was far from plug-and-play.

For instance, it was far easier to just edit the M104 value than to change the temperature and re-slice the whole thing, which could take an appreciable amount of time back then. Honestly, we were all working on the printers as much as we were printing. Knowing how to whip up some quick bed-levelling test scripts and/or demo objects in G-code was just plain handy. And of course the people writing or tweaking the slicers had to know how to talk directly to the machine.

Even today, I think it's useful to be able to speak to the machine in its native language. Case in point: the el-quicko pen-plotter I whipped together two weekends ago was actually to play around with Logo, the turtle language, with my son. It didn't take me more than an hour or so to whip up a trivial Logo-alike (in Python) for the CNC: pen-up, pen-down, forward, turn, repeat, and subroutine definitions. Translating this all to machine moves was actually super simple, and we had a great time live-drawing with the machine.

So if you want to code for your machine, you’ll need to speak its language. A slicer is great for the one thing it does – turning an STL into G-code, but if you want to do anything a little more bespoke, you should learn G-code. And if you’ve got a 3D printer kicking around, certainly if it runs Marlin or similar firmware, you’ve got the ideal platform for exploration.

Does anyone else still play with G-code?