daGHIZmo 's plotter is great. Over time I have made some changes.
1) The original arms are designed for beaded chain. This remix uses arms designed for GT2-6 timing belt.
I use these with a hook that press-fits onto the end of GT2 timing belt. the hook is 8mm wide, fitting in the hole on the end of the arm. If you do not have hooks you can pass the belt through the hole, fold it back on itself, and use a zip tie/zap strap. I prefer the hook because I can more precisely control the distance from the pen to the motors.
2) The original body had an M4 nut that was held in the plastic by being a friction fit. I updated part FCE.1501.01.005_fix_r01 (now r02) so that it holds an M4 nut.
3) The weight holder now has a lip that keeps the retaining ring from slipping off.
loaded in the previous STL. copied the outline. Tweaked the necessary parts.