Magnetic Rack for 8, 1.5mL Tubes

by acadey, published

Magnetic Rack for 8, 1.5mL Tubes by acadey Apr 24, 2013

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This is an 8 tube magnetic rack for 1.5mL tubes. These things are insanely overpriced and are a perfect thing to 3D print - the major cost is the magnets which are ~70 cents a piece. This design has little arm things that hold your tubes in place snugly and can even hold them in when upside down. I recommend using these magnets: http://www.kjmagnetics.com/proddetail.asp?prod=B842 and using some epoxy to glue the magnets in. The easiest way to glue them in is to glue an outer one first, then put a tube in to hold it in place, then do the same to the third position tube, then the second one can be glued in since it will have equal magnetism to the left and right. Repeat for the rest of the rack. This design is optimized to use less plastic and prevent warping during printing, though I still recommend printing a raft just so it gets started easier.

I updated this model with a different base (it now has more room for you to look at the beads when pipetting) and also a version where the tube grabbers are printed without an overhang as per suggestion in comments.

Also if you are a grad student and are trying to convince your PI to buy a 3D printer - making just a few of these more than pays for the printer itsself!

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Thanks acadey for the clear recommendations. But, what is the easiest way to not make a huge mess and get the magnets in place .. is it by using tweezers to place them? These are small magnets. Also, what did you use to apply the epoxy glue to the plastic or magnet? Thanks! :)

I actually used just regular super glue on my last one (or rather my research assistant did). She said it was pretty easy and not messy. Just do one at a time, doing every other one then the ones in between. Just hold the magnet in while the glue dries for ~30 seconds or so.

I was wondering if anyone has tested in the lab with beads the top to top magnets mentioned vs the side to side in the model here?

Specifically, the ones Moe1 listed.

Yes. These work and actually I believe are better. The side to side ones were a mistake (even though they work just fine). I am changing the text now.

Is there a design for 15mL conical tubes?

My research tends to use larger volumes for manipulating magnetic particles.


Hi acadey, love your design of the magnetic stand and am about to order some magnets. Why did you go for the side to side magnets http://www.kjmagnetics.com/proddetail.asp?prod=B824http://www.kjmagnetics.com/pro... rather than the top on top magnets http://www.kjmagnetics.com/proddetail.asp?prod=B842http://www.kjmagnetics.com/pro... and does it make a difference? Also, they have the top to top magnets in a higher strength (B52), do you think that will improve the stand? Cheers!

The non-overhang model has internal faces. Netfabb was unable to fix them, can you remove them please? Or provide some STEP/IGES files so I can edit it? Thanks

Sorry for the delayed response - I uploaded the sketchup files (where I designed them) Hopefully this will help.

Great design - Thanks acadey for the brilliant design - saved me a ton of money!

So I've had one of these printed on Shapeways (which works great) and I successfully scaled it down for 0.6ml tubes (which also worked great at 0.75 scale) on my own printer, but I've not been successful in printing this scaled up to 5.0ml (scaled up 1.53) Eppendorf tubes. I keep having warping issues with it, which is not surprising since the scaled up version is the exact same width as my build platform! This is really frustrating since from the one position which was not warped, the tube fit perfectly.

I was wondering if you would consider releasing a version of this with only 4 tubes?

It shouldn't be too difficult for me to cut it in half and be a 4-tube version.

Actually very easy - just did it! Let me know how it works out for you.

Awesome! I'll be sure to post pictures of the set.

So I just printed this to use in my lab, it works perfectly! Thank you so much for making this it was a great idea. Slight problem in that sometimes the tubes tend to pop out of the holder if you try to put them in all the way. I would love it if you designed a good pipette holder, perhaps also magnetic so you could attach it to a shelf above the bench.

A design for a pipette holder is here:


So I finally got around to posting these. They work well for our shelves and pipettes, but may need to be adjusted depending on the model / shelf ledge width you have. Here is the thing: http://www.thingiverse.com/thing:153334http://www.thingiverse.com/thi...

Hanging Pipette Holder
by acadey

Funny you should say that - we actually have pipette holders that attach to the shelf above the bench that were designed by a colleague of mine already getting heavy use in the lab. Right now they come down a bit low for my liking but are great for shorter people or anyone with a shelf a bit higher up. I have been meaning to design one that keeps them up a bit higher. I will design the other version and then upload them both in the near future.

Glad to hear this magrack is working out for you. To get rid of the pop-out problem we have a cylinder file that can take off a bit of the plastic inside the slots that seems to work out well, so maybe try filing it down a little bit.

How do you handle the overhanging piece? Interior support to print?

If you add some support yourself, it could be printed without that. It would not be in the way of the tubes

It actually prints it fine without supports. The overhang is actually at a gradient, so there is no large jump extending over empty space - it adds on ~1mm extension per layer, however that edge is never super-clean.

A support would certainly work and not be in the way. I am actually still tweaking this design and will post an updated version in a bit - I will play around with support ideas. Thanks for the suggestion!