Public Lab Research note


Prototyping flat-pack version of Desktop Spectrometer

by tonyc | October 14, 2015 19:11 | 2,285 views | 7 comments | #12303 | 2,285 views | 7 comments | #12303 14 Oct 19:11

Read more: stable.publiclab.org/n/12303


What I want to do

Right now the DSK version 3.0 requires a box, which means it has to go through customs and requires more expensive shipping options. The only parts that are not flat enough to ship in an envelope is the wooden block. My goal is to make workable model using only paper and that packs down flat enough to fit into the USPS regulation envelope (11-1/2"x6-1/8"x1/4")

My attempt and results

There are two approaches I've started on. One is a simple analogous replacement of the block. Basically, fold up a block and tape it down right to the bottom of the box. the platform is simply removed from the design. If velcro is required or desired, slap it right on the box. If movement/removal isn't needed, just tape the block right to the bottom of the box. The papercraft housing gains little rigidity from the platform, and IMHO, the platform is dead weight.

The other approach is pretty different, so I'll create a separate thread/note on it soon.

OK, so I mocked up a quick version of the block, giving it a bit more angular shape to increase strength.

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Questions and next steps

Next step is to create a flat file of the paper block and print it out to test. If it tests fine after refining, we can discuss whether this idea is worth creating a flat-pack variant Beta to ship, esp. to international customers.

Question is: does it work? How to make this design actually register at 45-degrees. Also, need to design the piece to carry the diffusion grating DVD. But that's easy enough to do separately.

another question is whether or not htis is strong enough when made out of black card stock material, or whether additional reinforcement is required.

Why I'm interested

This would make the fussiest kit easy to batch produce, ship for cheaper, and bring cost of production way down.


7 Comments

Here are some photos of another scale version. At the bottom is a new idea I want to create, but just parking for now.

This model has a narrow "nose" that would require the block be secured with tape to keep it from sliding around. It's also not at the right angle, etc. and was mainly made as proof of concept to see how strong it was.

Answer is, pretty darn strong, due to the triangular design. Definitely some thoughts to improve it as a box, as in tab placement, etc.

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But the main design goal, that it fit on the dead space on our existing die, seems withing range. P_20151014_155307.jpg

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I just put together a little test based on your idea, although it only includes the webcam stand and not the DVD so far. I tried to make more interlocks and overlaps and longer tabs. Especially made of a stiffer cardstock (FedEx folder), its quite stiff.

You can also cut stiff plastic sheeting with a Cameo or die cut, so that could mitigate any humidity concerns.

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This is a sketch of new version, with rectangular base. This would prevent the nose slopping around. Still tapers to a width equal to the webcam. Also, slightliy steeper pitch to the back, to allow it to be scooched up to the back of the box to get proper distance from the slit.

This is just sketch of the final shape, obviously. needs to be exploded out into cut file.

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Oh! comments crossed in cyberspace.

I like the angled design, for strength! I think we could figure out the angles by building it in Sketchup and unfolding it.

Link for cutting plastic on a Cameo: http://publiclab.org/notes/warren/07-30-2015/silhouette-cameo-desktop-paper-cutter-for-prototyping#c12301

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This isn't quite right dimensions, but proof of concept on the flared base allowing the block to register (with pressure from the bowed side walls) and on the lid being able to close with tapered sides allowing the flaps to get in. Might need to shorted the lid flaps a tiny bit to make it work together, but will have ot play with a better version built to dimension, not hacked together in 5 minutes.

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I'd also like to highlight the issue of the webcam USB cable pushing the camera -- we need a better way to manage the cable and have since the 2.0 version.

@ethanbass mentions in his OTK writeup:

I had a lot of trouble getting the camera to stay mounted. Even after doubling up the tape on the back of the camera, I found that torque from the camera's USB cable is strong enough to easily dislodge the PCB, if the spectrometer is not handled extremely carefully.

also:

Has anyone used the mounting holes in the PCB to screw down the camera? I think this would help a lot to stabilize the camera and improve replicability of the results.

I'm wondering if we could have a place that the cable threads into a kind of sleeve, and maybe even use an S-bend to really control it and not allow any tugging or anything to affect the mounting. I also agree that tape alone may not be enough. We used to use foam tape which was really solid, in that it was 'space-filling'.

Is this a question? Click here to post it to the Questions page.

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