Fully 3D printed quad: design, printing, maiden flight

In this post I outline a 260mm FPV quadcopter build whose frame I designed and 3D printed in my home printer. Carbon fiber is the material of choice for multirotors and other flying machines due to it being stiff and light. However, carbon fiber comes with many limitations in form. Usually frames made out of carbon fiber are flat sheets CNC cut to shape. Thus they are essentially 2D designs, with thickness being the only variable in the 3rd dimension. On the contrary, 3D printing allows full freedom to design in 3 dimensions, and therefore make better use of material strength. The 3d printed quad presented in this post is designed with this in mind to be stiff and lightweight, and also easily 3D printable.

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Rendering of 3D printed quad
Rendering of 3D printed quad

Read on for design and printing tips and the STL files for the frame.

3D Printed Quad Design

The design is a symmetrical frame, with slightly elongated X form. It is a “unibody” design, in that it provides all structural and mounting features in a single printable piece. The only additional component is a lid for the electronics compartment. That can be made out of a different material, e.g. a carbon fiber sheet. The arms are tubular with a flat top to help in mounting the motors straight. The wall diameter of the tube is variable to accommodate varying moments and point loads. For instance, the top part of the arm is thicker close to the motor mounts to accommodate for point loads from the motor mounts.

Assembled frame showing hollow motor arms
Assembled frame showing hollow motor arms

The arms blend with the central hub that houses all electronics (except ESCs) in an enclosed compartment. The wiring can be neatly arranged through the hollow arms and there are also holes to take the wires out if needed. The battery mounts on top of the frame, so that when level the frame sits flush. I found that the best place to mount the FPV camera is on top of the battery. This gives the best view and almost no props show in the image. An alternative mounting option is to mount the camera in front of the central hub, but this will have a large part of the image covered by props.

Read also:  Quadruped Robot Part II: Assembly, Electronics

Printing

The 3d printed quad frame is printable upside-down in one go on a large format printer (At least 250x250mm or 9.84×9.84 inch). It is also printable in smaller printers by splitting the frame in four. This way, each part prints one at a time, and connects with the others at the seams. If printed using 1.75mm PLA, I found that the easiest way to connect the parts is using a 3D pen with the same material. I ran the pen through the seams, pushing into the seam a bit. This created a strong weld that is almost impossible to break by hand. It also survived a couple of crashed during the maiden flight.

3D printed frame parts
3D printed frame parts
Frame assembly from four parts using brass guides
Frame assembly from four parts using brass guides

I found that PLA performs well, resulting in an extremely stiff frame with a frame weight of 100grams (3.5oz). This is with 100% infill. Reducing to 50% should shave off around 10-15 grams (0.4 oz). Printing in nylon or ABS could further reduce the weight to around 80grams (3 oz).

Frame after welding using PLA gun
Frame after welding using PLA gun

Hardware

The hardware used for this build is as follows:

Using this hardware brings the All-Up weight (AUW) to around 390grams, including battery and micro FPV camera.

Frame before ESC assembly
Frame before ESC assembly
Assembled Frame
Assembled Frame

Testing

The 3d printed quad has had it’s maiden flight, which went well overall. The craft flies well and is responsive, save for a few oscillations when descending. Certainly some PID tuning is in order to improve flying performance. Below a teaser of the build and a (rather short) maiden flight.

Files

The STL files for this frame are available on Thingiverse.

Conclusion

This post went over the build of a fully 3D printed quad that is stiff, light and easily 3D printable in any 3D printer. The design freedom offered by 3D printing is promising to achieve designs that make the best use of material possible.

Stay tuned for refinements to this design, as well as new mini and micro quad designs! And if you have 3D printed an aircraft yourself, make sure to share your experience in the comments below!

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