Small hobby aircraft and light plastic parts go hand in hand, and a 3D printing pen makes lightweight plastic things without the overhead of CAD work and running a 3D printer. So could a 3D pen create useful plastic bits for small quadcopters? [Michael Niggel] decided to find out by building his drone parts with a 3D pen loaded with ABS plastic. He mostly discovered that the created objects could politely be said to look like they were sketched by a toddler, but that’s not all he learned.

He found that in general creating an object was harder than the marketing materials implied. As soon as the filament exits the pen’s nozzle, the thin little molten line of plastic cools rapidly and does two things: it has a tendency to curl, and loses its desire to stick to things. [Michael] found the whole affair worked much less like ‘drawing in thin air’ and rather more like piping frosting, or caulking.

Nevertheless, [Michael] sought to discover whether a 3D pen could be used to make quick and dirty parts of any use. He created two antenna brackets and one micro quad frame. All three are chaotic messes, but one antenna bracket was perfectly serviceable. The 3D pen was indeed able to create a strangely-shaped part that would have been a nightmare to CAD up. The other antenna part worked, but didn’t do anything a zip tie wouldn’t have done better. The rapid cooling of the plastic from the 3D pen has an advantage: extrusions don’t “droop” like a glob of hot glue does before it hardens.

By now, [Michael] agreed that the best way to create a plastic part of any complexity whatsoever seemed to be to draw sections flat, build them up in layers, then use the pen to weld the pieces together and add bulk. The micro quad frame he made in this way doesn’t look any nicer than the other attempts, but it did hold the parts correctly. Sadly, it would not fly. Once the motors powered up, the arms would twist and the flight controller was unable to compensate for motors that wouldn’t stay straight. This could probably be overcome, but while the end result was dirty it certainly wasn’t quick. The 3D pen’s niche seems restricted to simple, unstressed parts that aren’t permitted to gaze up themselves in a mirror.

If you have a 3D pen, we’d like to remind you of this mini spool design whose parts are welded together with the pen itself. For bigger jobs, a high-temperature hot glue gun can be used to dispense PLA instead.