If you have access to a 3D printer, there’s a wealth of parts you can construct for just about any quad frame. While they’ve come down quite a bit in price and relatively cheap 3D printers can be good, a 3D printer is still an investment—as much in time as in hard costs. It can take a lot of effort to find, download, and convert a file for your printer. If you can’t find something you want to print that already exists, designing up a new part requires a lot of measurement and 3D modeling before getting it ready for the printer. Wouldn’t it be great if you could just draw out your idea in three dimensions?
3D Extruder Pens
An extruder pen promises to bring your ideas to life in three dimensions by letting you draw them out right in front of you. It’s an intriguing concept, available at much less than the cost of even the cheapest 3D printers. You load up some filament and start it up, and it extrudes the softened plastic in a line that cools off a couple seconds after leaving the pen. The plastic is still stiff enough to hold a line, but if you push it together it will blob up and create thicker areas. In this way, you can both draw out shapes and weld them together.
For our testing, we checked out the MYNT3D. It’s a well-rated pen, costs about $60, and it comes with enough ABS filament for a handful of smaller projects. The pen has a small display that gives you the current temperature. This lets you know when it’s ready to use and allows you to set it for different types of filaments. Other popular extruder pens include the 3Doodler, Samto, and Scribbler. We’ve seen budget pens listed as low as $12 at Banggood and Gearbest.
Using the 3D Pen
Drawing with the pen was more difficult than the marketing would have you believe. As soon as the filament leaves the pen, it has a tendency to curl. Drawing a straight line is a real challenge. Counter-intuitively, the filament doesn’t really want to stick to things when it comes out—and this exacerbates the curling issue. Smooth surfaces are troublesome to work on, as the filament will easily lift and misshape itself as you draw. MYNT3D recommends a surface recently coated with a glue stick, which is a bit awkward to create and work on top of. It seems that the best case for the pen isn’t really drawing in 3D space at all, but building up a scaffolding from parts drawn flat, then welding them together and adding bulk afterward. Trying to draw directly in 3D space amplifies the pen’s tendency to curl its filament. To build a 3D shape with any strength, one must pass the pen back and forth often, giving the appearance of a hardened mass of plastic spaghetti. Each extruder pen will have slightly different characteristics, but we imagine most will have these same basic properties.
As for the created object, its properties will largely depend on the material you selected. The MYNT3D came with ABS, which is a fairly rigid material once it hardens back up. It has a fairly good amount of strength, but little elasticity—it will resist bending, then irreversibly deform if pushed hard. The filament did not tend to snap and break if an object was built with more than one layer. Not all pens can be used at different temperatures needed for printing different filaments, so check before buying if you plan to experiment.
Antenna Mount 1
After fitting the EXUAV stack to the Floss 2, the antenna mount left something to be desired. Fitting a short-cabled Foxeer Lollipop made the problem worse, as the antenna flopped around dangerously close to the prop arc. I set to work on building a bracket in free space with the extruder. It looks like a complete mess, but the resulting mount does work well. It has enough rigidity to hold the antenna away from the props and I’m no longer worried about damaging it mid-flight.
Antenna Mount 2
Setting another Lollipop into my Wizard frame, I wanted to hold the antenna away from the carbon so I built another extruded mount off the side of the top plate. This mount looks just as sloppy, and doesn’t do the job as well as the one on the Floss. The plastic doesn’t grip the carbon nor hold its shape around the plate enough to be reliable. In this instance, a zip tie would have been a faster and better solution.
Micro Quad Frame
For a more intensive experiment, I constructed a new frame for an old micro quad. I started with the flat approach: laying out a few parts to scale and drawing some 2D planes with the extruder, then welding them together and building up the mass for added strength. The end result still looks like a rat’s nest of plastic. This method did produce a frame that was rigid enough to function. Repairing the frame after a crash would be as easy as blobbing on some additional plastic over the break.
Unfortunately, my frame would not fly. As soon as it powered up, it would go into a continuous yaw spin. This was because the motors wouldn’t stay aligned vertically. Because they leaned over, the FC couldn’t correct for the spin. A careful layout and alignment of the frame would likely produce a usable result, but the effort involved is far beyond what can be done with a quick free-space doodle.
An extruder pen has its uses. The antenna mount on the Floss 2 is a great solution that was quick to create and custom fits the exact parts I’ve selected for the build—but the success of the mount relied heavily on its simplicity and in being located in an area that doesn’t take much stress. You could use it to build up flight camera mounts, small brackets for receiver antennas, or tidy up cable routing. But in our opinion, with falling prices of 3D printers, it’s a tough sell. While a 3D printed part takes more investment and effort to construct, the difference in quality and utility outweighs the cost and ease of use of the extruder pen. Not to mention the appearance—unless you happen to like the “scribbled into being by a 3-year-old” aesthetic.