1. The item on thingiverse isn't referred to as a 3D pen. 2. Extrusion is the mechanism through which most 3D printing works. In this case, the extruder is att

1. The item on thingiverse isn't referred to as a 3D pen. 2. Extrusion is the mechanism through which most 3D printing works. In this case, the extruder is attached to your arm rather than to a machine.