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by TacticalCoder 32 days ago
Amazing: I'm watching lots of homemade builds atm.

I've got a question: why CNC milling and not just FDM 3D printed parts? TFA doesn't talk much about it except saying she went to a machine shop.

> 2. CNC milling forms out of G-10 fiberglass (arms) and 5mm carbon fiber (body)

TFA also says this:

> The solution for this is to 3D print a 0-tolerance assembly jig to hold the arms in perfect position while the center of the drone is superglued together.

Why not 3D print it all?

There's this guy who built a drone that can fly for 3 hours and cover hundreds of miles, 3D printed at home on a $250 printer:

https://youtu.be/e7AIKGDrlgs

Then there was the $200 K quote for the body for a car that just did Pike's Peak with a four times Pike's Peak champion and instead the team... 3D-printed the car's body at home (something like 40 parts, assembled together), which cost them less than $2 K to make (1/100th of the quoted price for the car's body). Here's the vid where they print all the parts (on a $1500 consumer printer):

https://youtu.be/nt85nTMnY1w

Basically: why CNC milling and not 3D printing at home when many drones enthusiasts (and now too people building race cars) simply print parts at home on a consumer-grade 3D printer?

3 comments

For "copter" style drones, 3D printing is basically a "noob" meme at this point; everyone thinks it's a good idea, tries it, and realizes that it's actually really hard and doesn't work.

Copter-style drones are exposed to vibration across a huge frequency range in every axis, and it's almost impossible to avoid really nasty resonance issues using generally-printable FDM filaments and "standard" design techniques; it's a lot easier to just use super-stiff carbon fiber and CNC it.

For planes, like what you linked, 3D printing is more "plausible" than for copters but also not really practical; you can 3D print a good plane, but plastic lacks the durability and favorable weight characteristics of foam - plastic planes tend to be "one time crashed" while foam is easy to repair, restore, and rebuild.

3D printing isn't stiff enough for a larger drone like this, you'll get flex which will upset the PID loop and cause it to be very unstable if it even flies at all.

You'll notice on your 3D printed drone link that the actual multirotor part is carbon fiber tubes. The motor mounts and other brackets can be 3D printed without issues.

Stiffness. Important for how the frame behaves under load and buffetting etc.
^^ This was why I opted not to 3D print the whole thing :)