Elegoo Neptune Pen Adapter

Description

Pen plotter adapter for the Elegoo Neptune 4 PlusThis is a small three-part adapter that clamps a ballpoint pen cartridge to the extruder of an Elegoo Neptune 4 Plus, turning the printer into a pen plotter. I built it to write postcards and draw single-stroke SVGs, but it'll write or draw anything you can turn into G-code. It should fit other printers with a similar extruder, but the dimensions are tuned to the Neptune 4 Plus, so you may need to adjust.The adapter has three parts:Main body — wraps around the extruder and holds the pen cartridge along with a spring. The spring is the important bit: it lets the pen float and push down slightly onto the paper, so you still get consistent contact even if the surface isn't perfectly level.U-shaped spacer — sits on top and presses against the extruder. It spreads the load from the screws so they don't bear directly on the extruder.Spring clamp — a tiny part that holds the cartridge's spring in place.You'll also need a standard ballpoint cartridge and its spring, plus a couple of screws to hold it together.I wrote up the whole build — including the software side and how to stream G-code to the printer without it crashing the pen into the bed — here: [https://severinbucher.com/posts/writing-postcards-with-a-3d-printer/].