O Pen

As the parts operate in a cramped space, it works perfectly only when all zits and unnecessary parts of the surface and inside of the printout are removed.
If you want to convert it into a mechanical pencil, prepare it 4mm longer than the D1 refill.
You can express the surface texture of various patterns using bumpmesh.com.
0.6T Ø8mm spring.
0.4 nozzle, layer height 0.22, no support.

https://www.youtube.com/watch?v=1qD828PmsjY