Someone Finally Put an Automatic Toolchanger on a Pen Plotter
Prashant Sinha's Limn is a pen plotter that features an automatic toolchanger, as they all should.
Pen plotters are neat and cool. From a control and motion standpoint, they’re basically identical to 3D printers. But instead of spitting out molten plastic, they draw on stuff. However, I’ve never seen a pen plotter that can swap between several implements — at least not outside of commercial machines used by drafters. That is why I was very excited to see Limn by Prashant Sinha, which is a pen plotter that features an automatic toolchanger.
The benefit of an automatic toolchanger on a pen plotter is really, really obvious. So obvious, in fact, that I’m surprised it isn’t the norm. Cricut machines can usually switch between two loaded tools, but that is about as good as it gets. Limn, however, can swap between five different tools during a job. Those can be different pen colors, different marker sizes, or even entirely different writing implements. Mix and match pens, pencils, markers, and highlighters to your heart’s content!
On top of that, Limn incorporates many of the advancements we’ve seen from the 3D printing industry in recent years. It has CoreXY kinematics and even runs Klipper. Most of the parts were salvaged from an old Tronxy 3D printer, so that makes sense. The controller is a Melzi V2.
The star of the show — the automatic toolchanger — also borrows a lot from 3D printer design conventions. Sinha was inspired by a toolchanger created for the RatRig VCore. Pens go into simple holders with magnets and protruding pins, so the carriage can drop or pick up a toolholder with a couple of quick motions.
The result is much more versatile plotting… with pens. It really is very obvious in retrospect and hopefully all pen plotters from here on out will feature toolchangers.