If we told you somebody built a 3D printed go-kart, you’d expect to see a certain sequence of events. A bit of work in CAD, a printer montage, then some assembly. That’s not the case here.

The solution? A Mini Spool System for 3D Printing Pens, with which you can use your 3D printing pen to weld together the parts after printing them. The unit holds 1.75mm filament coiled under its ...