# Centrifuge Spins Samples Up To 400g

We were curious to see when someone would use a 3D printing pen for something other than art. It might not look very pretty, but [Techmeology] “drew” this centrifuge mount for a motor in order to spin some test tube samples.

It’s kind of hard to see in the picture, but the test tube holder “arms” are detachable, and when the motor spins up it opens like an umbrella. Pretty much all the parts are recycled, and the motor came from an old appliance, making the cost of this project negligible — a good use case for any remote location that might require custom parts or repairs.

As for actually fabricating functional items with the 3D printing pen, [Techmeology] offers some useful tips for drawing brackets on his site. For instance, wrap the parts for which you need mounting brackets in paper. This provides a barrier while drawing your design in molten plastic.

There are a few other tricks that can be performed by 3D printing pens, like using them to “weld” parts back together. If you don’t already have one you could just use a soldering iron for this purpose — or make your own 3D printing pen using LEGO and a hot glue gun.

## 19 thoughts on “Centrifuge Spins Samples Up To 400g”

1. RÖB says:

I don’t believe 400G

1. Truth says:

G-force= 1.12 x R x (RPM/1000)²

R=130 mm
RPM=1667 (half-rotation of the centrifuge takes 18 ms)

The numbers all add up to 404g, what is the problem ?

1. 0x10000 says:

Hooray for math!

2. RÖB says:

If the tube and holder are 100g then the centre piece if holding the equivalent of opposing 40kg loads and I cant see a piece of plastic holding that load.

1. oodain says:

plastics are fairly strong materials by weight, especially considering how most deform instead of catastrophically failing.
40KG isnt much for that amount of plastic.

1. Ryan says:

If the 40Kg estimate is correct, I agree with RÖB. I have dealt with 3D printed parts extensively. I can’t see a 3D printed part of this quality holding that load.

2. thirtyone says:

Okay guys, “g” is a terrible unit when it comes to how much force something can take. When people think gs, they think about how much force a “g” is for a person. One “g” for a 75kg person is about 750N, 75kg-f, or 165 lb-f, and 400 “g”s on a 75kg human is some absurd quantity, 300 kilonewtons, about 30 (metric) tonnes, which is and absurd amount of force. At this scale, 400 “g”s for a 5mL test tube (guesttimate) with 5g of solution, say 5g of test tube (overestimate) gives us maybe 10g. Suppose it’s all on the outside, somehow, magically. 400 “g”s on that, (10m/s^2 * 400 “g”s * 10g) is 40 newtons, or 9 lbf. Actually, that’s not terribly large, but it’s not terribly small either. I’d be wary of its long term reliability. But the numbers do work out to 400gs. The actual force on it is dependent on the weight of the load, which can be quite small give that it looks like a pretty small test tube.

2. AKA the A says:

Buuuut, if you think about it, the 400G is ONLY at the tips of the arms, the closer you come to the center, the less acceleration ;-)

1. RÖB says:

I think that is where the maths went wrong. The radius in the formula mentioned is the radius to the centre of gravity and not the total (maximum) radius of the rotating part.

3. jacques says:

and at 3000 rpm, 1600G

2. murdock says:

If you were to fill the test tube about 1/2 to 2/3 of the way full of water the offset weight would easily be five grams or more. Even though a lot of it won’t be at the farthest point of the radius, you could easily get a 3 pound offset load at full speed. I believe it can generate the forces claimed, I just don’t think it can hold it long.

3. Galane says:

Is the power switch labeled Safe and Decidedly Unsafe? One thing this may have going for it is the continuous filament going around like a spider wrapping up a dead fly.

4. yetihehe says:

I drew a small bracket to hold rpi and camera on a toy drone, does that count as non-art?

5. scuffles says:

Man when I have used 3D printers they have been safely in a fume hood. They probably aren’t terribly bad for you but they certainly aren’t super healthy either and man do they stink.

tl;dr
I don’t think I’d want to sit there manually doodling that thing out :P

1. operative says:

they stink. and are unhealthy. but only when printing with ABS.
PLA on the other hand doesn’t smell and is safe to print without a fumehood.

1. PLA certainly smells (something like maple syrup) and gives me a headache.

I’ve read that no filament is safe to print due to nanospray, but that could just be this decade’s version of the nuclear boogieman…

1. PLA itself is likely safe, even if you are inhaling a so-called nano-spay (couldn’t find a reference on google, so I’m assuming its similar to ultra-fine dust) since it eventually degrades into lactic acid. That’s why it can be used in temporary medical implants.

The big unknown is the dye’s and colors the manufactures use, and any other potential additives.

6. This is perhaps the scariest project I’ve seen all October so far.

7. This Guy says:

Great. Just keep it far way from me if someone wants to use it. Very far preferably.

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