el-cheapo tabletop minifuge
by tinytim, published
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I am a bit concerned aboutÂ what happens if you spin this unbalanced. All the centrifuges I've ever used have a flexible mounting for the motor so small vibrations don't shake it apart. If only we could print in rubber...
I am sure many motors rotate faster than 16k, but I did not have any of them lying around (on the long, grey rainy week-end I designed this thing; didn't feel like going shopping for sth. more suitable; I just wanted my immediate design and 3D-printing "Fix").
I would suspect the rotor to withstand greater RPM's, but I have not tested it to failure (yet).
It should be fairly easy to edit the mesh to fit a dremel or other motor
hmm, 16K is not that much isn't it? If you use a (fake) dremel for a motor, you can reach 35K.
On of the things you should do though is balance your rotor, preferably print it in ABS to prevent shattering if something goes wrong, and (most important): put a casing around it.
Perhaps not needed for your speeds, but better safe than fishing PLA shards out of your eye?
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you will need:
1x graupner speed 400 motor (or similar sized motor, available at your local model shop)
1x 220V switch
1x 220V to 6V trafo (I used a small print-trafo 6V, 3.2 VA, size 35x42x30 mm)
1x bridge rectifier
1x poti suitable to regulate your motor speed (depends on your motor's ohm)
2x 3mm screws (about 5mm long)
2x 3mm threaded rod (about 1cm long), with a slit sawed into it (cheap replacement for a headless screw)
2x 3mm nut
...and an electric cord and basic soldering skills to go with it
wire the whole thing up and let the thing turn! (preferably inside a steel pot for the first test runs)
according to the manufacturers specs, the motor does 16.4 k rpm at 7.2 V (I'm running it at 6V). A first test (10 minutes at full rpm, fully loaded with 6 water-filles 1.5 ml reaction tubes) worked out fine.
printed in PLA, 1,2mm wall-size, 50% infill for all parts.
0.2 mm slicing using cura & an ultimaker
WARNING: if the rotor is not printed carefully, it may break during centrifugation and cause harm! BE CAREFUL. So far the thing works fine for me, but I was quite pedantic during the printing process and threw out multiple so-so attempts.
ROTORS TURNING AT HIGH RPM's ARE DANGEROUS!!!!
the rotor and casing bottom can be printed without support material. The casing top does need it.
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