Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:3444190. This is a more robust pen holder for an Arduino drawing robot, designed to be printable in an upright position without supports (so the layer orientation will result in a stronger print). Previously I was using this design, which worked well for a while: https://www.thingiverse.com/thing:2058866 Unfortunately, after a while, the pen holder snapped as shown in the picture (perhaps due to insufficient fill, poor layer adhesion or rough handling), hence this new design which I hope will be a bit tougher. Time will tell. The original drawing robot design is here: https://www.thingiverse.com/thing:1517211 This needs an M3 screw to secure the pen (I'm using an M3 x 20mm socket head cap screw, which works well). It helps to wrap a turn of insulation tape around the pen before tightening the screw against the pen.