I am trying to make the world’s fastest nerf gun right now, and I am going to use a flywheel spinning at 625,000 RPM to accelerate the Nerf Rival balls, but I don’t know what filament to use for it. I have a Bambu Lab A1 Combo with a 0.2mm stainless steel nozzle, 0.4mm stainless steel nozzle, and a 0.6mm hardened steel nozzle. My mom will not let me use any filaments that are carbon fiber reinforced because they are “highly toxic” and she is worried that the carbon fiber will get stuck to my skin, so carbon fiber filaments are not an option. I am trying to find a strong enough filament to print gears that will be spinning at 625,000+ RPM, and I do not have the option to use an enclosure. Does anyone know of any non-toxic filaments that will work for this project that do not require an enclosure?
Besides likely killing the target, how are you going to generate that speed of rotation?
With an open frame printer and an unwillingness to use reenforced materials, I suspect you will not achieve your goal.
If you wish to try, you must consider the position of the layer Ines at all times in order to design in the strength where possible.
Don’t print a barrel pointing up as the sheer force will break at the layers meaning the barrel will snap easily.
Your printed gears will need to be very resilient, I doubt PLA or PETG will get close to the strength you require for anywhere approaching the desired speed. You can print small things in ABS, but, your open frame limits the size of parts.
Have you made this part?
That is a huge increase from an N20 motor. It already has a gearing system to increase the base rotation from the motor to the pole, you plan on multiplying that even further by 625 times.
I do nit think the N20 motor has stuff torque to drive the speeds you need. It is a hobby motor, you will need something stringer to start with.
I am not an expert though, I may be wrong hopefully someone with experience will chip in.
I have figured out most of the small things like that, but do you of any filaments that would work for what I need?
I mentioned already.
I only have one thing to say and you’re not going to like it:
“You’ll shoot your eye out, kid.”
Have you read this?
Without an enclosure and appropriate printer, you are stuck with pla, petg and maybe asa.
Good luck
You really have an affinity for N20 motors…
Suggest watching this video as it is a similar project and will give you better indication of what the level of hardware needs to be to accomplish a task like this.
I am going to offer thoughts on how I would approach this problem IF I HAD TO PRINT IT. That said, do not take this as an endorsement of 3D printing a rotating mass that is going to spin at over a half a million RPM. No matter how light the object, that is a lot of inertia. If it broke apart in an open space, the pieces could act like shrapnel and hurt you or others. Only do this kind of work with the knowledge of that Mother you mentioned!! And, in an environment with adult supervision, with testing safeguards and the proper PPE to protect you from flying debris.
The CF filaments are not stronger (they are stiffer). This is a big misconception (well, ok, sometimes they are a little stronger). And, the interlayer adhesion is worse in most cases. Mostly the CF (or GF), makes hard-to-print engineering filaments more dimensionally stable (less warping by far), and therefore much easier to print. If I were making a spinning mass I’d use a non-CF filament because interlayer adhesion is likely to be the most important thing. Even a very strong filament will have an interlayer adhesion (z strength) that is only 1/2 to 1/4 as strong as the part in the X and Y direction. I’d print them laying flat on the bed, with near 100% infill, and use a ton of perimeters so that the teeth are firmly anchored into the body of the gear.
For gears you need a strong filament, but you also really need toughness (known as impact resistance, or the ability to bend before breaking) and surface lubricity(a slick material) for abrasion resistance.
These are the properties of the highest-end printable nylon, PPA. It also has resistance to heat up to about 200c, which is important in any application with a lot of friction - friction melts stuff.
PPA is the strongest filament you can print with a 300c hot end - by a mile. I’d print it slow, with the max temp, and with no fan if you can get away with it - you want to maximize layer adhesion. Then, I would Anneal the finished print to further increase it’s strength - and bond the layers even better.
The problem - It may be the easiest nylon to print, but it is still nylon. It will warp. For anything but very small (1-2") parts, you need an enclosure with a minimum temp of 45-50c. You could achieve this with a small grow tent and a heater.
SirayaTech makes a non-CF PPA for $55/kg. This is much cheaper than any other brand, and it is great stuff. I print the CF version, and it is amazing. like metal-level amazing.
First, tell you mom to stop reading the National Enquirer, just because it’s on the Internet doesn’t make it true.
I applaud your ambition, kid. 
Pushing the envelope is how progress happens—but are we going to be reading about you in the paper next week? 
On one hand, I want to encourage a young mind to explore, innovate, and not let adults tell them what can’t be done. After all, Einstein, Musk, Zuckerberg, Jobs, and Gates all made their marks before turning 30.
On the other hand, the ‘dad’ in me can’t ignore the risks. At 625K RPMs, you’re dealing with immense kinetic energy. You don’t need gunpowder to cause serious injury—trust me on that.
I strongly recommend taking this in stages. Start by building parts of the device with PLA and test them thoroughly. This approach will help you understand the limits of the material and give you the hands-on experience you’ll need to refine the project. It’s a safe way to learn what works and what doesn’t.
But if you’re just downloading plans to impress your friends, well… make sure your affairs are in order and have a good attorney on speed dial before you try it. Seriously. 
My point is, don’t be reckless. If you’re determined to build something dangerous, make sure you thoroughly understand how it works before trying to create it yourself. Take it from my cousin One-Eyed Gus. He thought he could design a better crossbow using scrap pine and leather laces. That is, until he tried to cock it. Now, we call him One-Eyed Gus for a reason.
I applaud your vision. Next is gaining understanding as to what this vision entails and what key requirements but also dangers arise from that. From my experience, two very different roads go best hand in hand.
Th
- The fun road is trual by error. But learn to run before you walk. Start with a single gear, driven by hand or an small motor. Then add another, etc to better understand what cause leads to what effect. This road may not lead you where you initially wanted to go, but it’ll be fun an give you unique insights whoch you are likely going to build on future visions and ideas. It’ll definitely place you ahead in future Physics and Engineering classes
- The seemingly boring but incredibly useful road is to ask yourself a few key questions , research a bit and try to find a frame of reference or even do basic calculations. For the former, you may want to compare your the rpm to typical jet engines. And then compare power. For the latter, at 625,000 rpm, how large does a disk need to be to become supersonic at the edge? If it broke and 1/4 of it came loose, what energy would this disk have? What caliber does this correspond to?
=> I think you have an interesting project which is worth pursuing for the sheer joy of achieving it. But start small and work your way up. You can achieve something worthwhile without going into military grades 
And you never know what it’ll i spire you after that.
I make gears all the time. I initially bought a 3D printer for the purpose of creating gears and connecting machine members. PLA works really well for gears. So does nylon. All plastics are of a class of strength. That is to say that pretty much all plastics have a strength that is in the ballpark of other plastics. If PLA is not strong enough for your gears, the strongest most expensive filament will only be marginally stronger. It is why in commercial products, plastic gears are used for low torque applications while brass or steel is used where strength is required.
That said, you can get professional PLA from companies like Overture and BASF. The PLA pro varieties, intended for engineering applications, are as strong as ABS and stronger than carbon fiber, all without the potentially toxic vapers. Where regular PLA breaks when stressed, the pro varieties have a little give and hold up. The downside to PLA pro is that it doesn’t handle heat as well as nylon or ABS.
I’m gonna guess there will be friction heat at half a million RPM 
I’m guessing that the whole thing will fly apart well before it reaches 625K rpm. 
I think the energy required to power a gear ratio that will get you to that RPM, even with a very lightweight object would be much larger than the motor being proposed