3D Printed Drone

Hi, I'm a second-year computer science student and have been working with drones for a few years now. I started in high school with some competitions, and I built my first drone over this past summer. This fall semester I decided to make another drone as a part of my school's robotics club. I will be outlining my process of parts selection and frame design in this guide.

1. 3D Printer (Used my school's Ultimaker S5)
2. Choice of filament (PLA for prototypes, ABS for final draft)
3. CAD software (Autodesk Fusion)
4. 4x Drone Motor
5. 4x Propeller (can be printed, but I suggest buying)
6. Electronic Speed Controller
7. Flight Controller
8. Receiver (your choice, I used ELRS)
9. Lithium Battery (I used a 3S 850mah)
10. RC Controller with transmitter to match receiver
11. Various Fasteners

Since the frame of this drone is going to be 3D printed, that is going to be the last part we worry about. It can be designed as needed to accommodate whatever parts you get, and as I did you should be able to easily perform several iterations of designs to meet your needs.

I find that it's easier to base the whole build around the flight controller (FC) and the electronic speed controller (ESC) since those two serve as the brain of the system.

ESC: In my case, I already had an ESC from a failed project the robotics club had attempted in the past. This ESC was rated for 3S-6S batteries and used a 30.5mm square mounting pattern. The model was the SpeedyBee BLS 50A. This seems to be pretty standard and both of my drones have similar specs.

FC: Since I already had an ESC, I decided to find a FC with the same mounting pattern with support for all the main drone firmwares (Betaflight, Arducopter, and INav) so I could modify the drone as needed for future projects. I decided on the RadioLink F405 because of the price point and since it matched the above specs.

Motors: These I also already had from the club. There are plenty of guides online to choose an appropriate motor for your drone. The motors I had were Readytosky RS2205 2300kv motors. These motors were meant for a larger drone than I planned to build, but as long as I found the right propellers and designed the frame properly I figured I'd be fine. If I hadn't gotten these motors for free I would have gone for motors much smaller and lighter like I had in my previous drone with 1404 3000kv motors.

Propellers: I wanted my drone to be fairly small and lightweight. Under the legal limit to be able to not register the drone with the FAA while still being large enough to safely fly outdoors. Since I had already built one drone and was happy with the size, I figured I'd go with a similar size with 3.5" propellers. I found that the Gemfan Hurrican 3520 was one of the only options that was both small enough with support for a large enough motor shaft.

Receiver: I already had a remote/transmitter from my previous drone and figured I could just use it with both drones, so to match the transmitter I got a small, lightweight ELRS receiver from BetaFPV.

Battery: I was worried about weight with this drone since the frame would be 3D printed instead of purchasing a carbon fiber frame like I did last time, so I chose to get a small, 3 cell battery with only 850mah capacity, which could still sustain several minutes of flight, and if the finished product was light enough I could always get a larger battery later on.

RC Controller: Like I mentioned above, I already had a controller, a RadioMaster Pocket EdgeTX. It was just the cheapest option I could find at the time.

Fasteners: I had some different screws and nuts around, and got a battery strap for free with an order of some parts.

Ultimately I optimized this build for cost. All the parts that I ordered came out to be $82, but with the value of the parts I already had added the cost would be between $200 and $250.

My frame design went through 3 major iterations, with many changes made between prints. All 3 iterations are above in order. The shortcomings of the first 2 designs were really just from me not thinking about certain measurements, so I'd recommend paying particular attention to the length of all wires included with your components and the screw sizes you need.

Design 1: Many of the aspects of the design were copied from typical FPV drone frames, with modifications of course. If you look online for FPV drone frames you'll see many similarities. I stripped away the camera mount from the front made mounting points in the base of the frame for the FC and ESC in the middle, the motors on the arms, and 6 points near the corners to connect the top and bottom of the frame. You will notice extra branches between the main body and the arms of the frame, and there are also feet on the bottoms of the arms, Both of these were added to improve the strength of the frame since it is 3D printed and not as strong as a traditional frame. There are many triangular holes in the frame to reduce weight and printing time. I found that the holes for the screws were too small due to thermal expansion while printing, and after drilling out those holes a bit to confirm that I could fit together the roof and body I widened the holes and reprinted.

Design 2: The only real changes I made were that I widened the holes a little. Unfortunately I found that the motors needed wider screws, which is why I mentioned above to check all measurements. It was also at this stage that I found that the wires for the motors were too short to reach the ESC, so rather than extend the wires I decided I'd just adjust the length and angle of the arms on the next iteration since I'd need to widen the holes anyway.

Design 3: This is the final iteration. At this point the roof of the frame could be mounted by inserting nuts into holes in the standoffs. I had made slots in the arms for mounting the motors instead of just holes because the motors used a 16x19mm mounting pattern meaning, the distance between the holes was not the same across the X and Z axes, and I could easily copy the same frame pattern between the arms if I used slots, with an added side effect being that I could share the design for anyone else to use as long as their motor mounts fell between 16-19mm and it could easily be modified to widen that range. The biggest change that I made, which I mentioned above that I'd have to do, is that I changed the angle and length of the arms of the drone to account for the short motor cables. You may notice that the triangular holes in the frame in this iteration are not the same as in the other two, and that is because the entire frame was redesigned from the ground up, only copying over key elements. When I went to assemble the drone with this frame everything went together perfectly and I decided I could go on to the final print after doing a test flight.

The assembly of a drone this simple is very straightforward, and I was able to complete it very quickly with only soldering 24 connections and connecting 1 cable, though that cable did need some modification.

Connecting the Battery: I had an XT30 pigtail to connect the battery with as well as a capacitor that was to the ESC manufacturer's specifications. These connections took a while because of how thick the battery connector was and how large the solder pads were, but overall it wasn't that bad.

Connecting the Motors: The motors were already attached to the ESC, but whoever soldered them before had no idea what they were doing so some motors were upside-down and the motors were directional but whoever soldered them before hadn't considered that, so I just redid the motors and put the wires at an angle so the wires would reach further.

Connecting the Receiver: Although the wires for the receiver were very slim, this part was fairly easy because no wires had to cross over, all of the wires could be run straight from the receiver to the FC, using the wiring diagram for the FC to know which pads to use.

Connecting the FC and ESC: No soldering was required for this part. The FC included a cable that could be plugged in on each end, but the wires did not match up directly, so I had to carefully pull the wires from the connector and rearrange them for proper power delivery and communication.

Frame: As I mentioned before, I put nuts into the standoffs of the frame, 2.5mm nuts specifically, screwed together the top and bottom of the frame. The FC, ESC, and motors were mounted using 3mm screws and nuts.

Not counting the time it took prototyping the frame, it maybe took 2 hours maximum to assemble the whole drone and only needed basic soldering skills. The longest part of this project was honestly trying to budget parts, so if the cost isn't a big factor then you should be able to build a drone yourself fairly easily.

The frame I made can be found here.