Pen plotters are popular builds amongst DIY CNC enthusiasts ... place it on, rolling on a small wheel. It’s likely not ideal for accuracy or performance; we could see the machine itself skating ...

There is a very clever and very inexpensive way to add a 4th axis to a CNC machine, though, and after a bit of fabrication, he was able to add a ‘rolling’ 4th axis to his machine. [Bob]’s ...