Pen Holder for for Converting CNC Laser to a Pen/Drawing Plotter

This includes the STL files for a pen holder using a standard size servo to convert a CNC laser (YunLee or generic Chinese) to a pen plotter.

The pen clamp slides on the two 3/32" rods attached to the base. The pen clamp back section (Holder) has brass tube bushings in the bosses. The assembly is pulled up with a rod/wire with a lock collar (not visible). The spring on the longer rod is from a ball point pen and is adjustable with another lock collar.

I used brass bushings because I had the tubing on hand. However, I think it would work fine with the rods riding in the plastic. The Either way, there is some trial and error getting a good fit that also slides freely. The pen mechanism should drop down under its own weight.

The pen clamp is slotted to allow up to a 45° angle. The hold-down thumbscrew I had on hand. The spacer is in the STL files. The thumbscrew that secures the pen is a random 6-32 screw epoxied into the knob included in the STL files (2 sizes). The knob has a square pocket for the screw head and epoxy.

The Pen Clamp STL has been revised from the C-clamp style to a full loop.

Note: This project requires a GRBL version that enables servo operation in place of the laser, using an Arduino + CNC shield in place of the YunLee controllers which use ARM chips.

There are a couple of GRBL options to control the pen up and down. I'm using this one that works with Inkscape's Gcodetools extension:
https://github.com/bdring/Grbl_Pen_Servo

I found it on this in-depth Instructable tutorial:
https://www.instructables.com/How-to-Control-a-Servo-Using-GRBL/

I'm using the latest Inkscape version, 1.3.2.

PLA. Use 40% infill for the pen clamp to prevent flexing under pressure of the thumbscrew. To slide freely it needs to be sturdy enough that the bushings don't bind.