Public Lab Research note

Assembling the Oil Testing Kit Cuvette Frame

by mathew | April 07, 2015 23:46 07 Apr 23:46 | #11751 | #11751

This cuvette frame's design notes are here, along with previous versions and other design ideas. It can be used with this procedure

Download and cut out all the five pieces:




I recommend a card stock like a cereal box. lines can be scored with hard presses of a pen, butter knife, or other smooth blunt thing.


Start with the main frame piece and pre-crease the folds:

IMG_20150406_170830.jpg IMG_20150406_170943.jpg

Slide the long tab through the opposite side wall, and then tuck in place:

IMG_20150406_171018.jpg IMG_20150406_171129.jpg

The long strip with triangular holes should be folded up like this:

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Don't completely fold up this little part, just fold along the length-wise fold:

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put it together by putting the M-folded sheet into the box, and sliding the V-folded strip through the center. Make sure the matching rectangular cuts are on the correct side, so that we can slide the laser attenuator in place.


IMG_20150406_171630.jpg That rectangular cut in the V-folded strip can get caught on the last little push through. watch it.

The last centi meter is the hardest to get through.


once through, push the tabs in place on both sides:

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Alright, the frame is almost done! Now to put the cuvette holder in place.


Pre-fold the cuvette holder:

IMG_20150407_140244.jpg IMG_20150406_185914.jpg IMG_20150406_185925.jpg

This fold is the trickiest. Push inwards on the center section while folding. It will pop in place. Crease all the way flat:


Now lets put it in the frame:

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fold the bottom flap up and through, and slide the front of the cuvette holder down on it:

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Now close up the other end of the frame:


Now assemble the laser attenuator:

IMG_20150407_150115.jpg IMG_20150407_150347.jpg IMG_20150407_150502.jpg

Place in front of the spectrometer, add cuvettes and a 405nm laser pointer, and you're done:



These instructions are really great, except I feel like there's a gap between the laser attenuator and the completed assembly.

"Place in front of the spectrometer", which I assume refers to placing the laser attenuator in front of the spectrometer, is a fairly ambiguous instruction. The completed image doesn't show a laser attenuator (at least not obviously). Could you clear up where the laser attenuator goes?

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It looks like the cut files are both the same, but I dug out the 2nd file from the staff design folder -- is this it?


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that is the latest file, yes. its only slightly modified for die cutting.

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Super tnx!

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Awesome. This went well, although unlike the laser cutter, my Silhouette cutter doesn't remove material, so the V-shaped piece didn't quite fit. If we did this as a production run we'd want to make it a tiny bit narrower for a smooth fit.

I did mine in green because I am out of black paper (some is shipping to me) but it was easier to photograph, and a few steps where I wasn't sure, I took an extra photo once I figured it out. For example, I put in the V-shaped piece (we should number the pieces!) backwards despite the warning, because i misunderstood which direction the photo was from.


Also, I think once we move to larger batches, some printed-on guides like "fold so spot A touches spot B" could be helpful (as above), and "ensure that the "B" end of all three pieces are on the same side" or something.

Very very clever design, Mathew - especially seeing it all come together in sequence. Love it -- i actually had a pre-assembled one so this was my first time all the way through.









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I wonder, for usability, if the V piece and the M-folded piece can have slits for the attenuator in both sides as well as their being an extra cutout for the laser pen handle on both ends of the M-folded piece. This would be helpful in the case where someone aligns one or both of those pieces backwards (despite the instructions). If both of those pieces are symmetrical, then there is no orientation requirement that needs explaining and understanding.

(Ya, I goofed, but am weary to dismantle the frame since that risks ripping the paper and making it less rigid. I'll probably just slide the attenuator in closer to where the cuvette sits.)

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This is great! 20 people replicated this construction in Cuenca, Ecuador by printing out their own on heavy black paper.

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