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Laser-cut the Desktop Spectrometry Kit v3 box

by warren |

In doing some tests with the Desktop Spectrometry Kit 3.0, I sent a test print to Ponoko.com -- a site that does mail-order laser cutting. I adjusted the design files to the colors they use to indicate cuts versus score lines (cuts that don't go all the way through, and act as creases to fold on).

https://github.com/publiclab/spectrometer3/blob/master/production/lasercut-ponoko-15x15.svg (note that this isn't full scale -- read on)

This is a work in progress, but it arrived, printed on the 15x15" square size (linked to above), but I messed up the scale, so it's a bit small. It would probably work fine as a spectrometer, but wouldn't fit the boards we're ordering, so I'll have to make changes:

image description

Issues

Scale: I need to adjust the size so it prints at the same size as the standard kit. Oddly Ponoko's size for their standard black paperboard is 15x15, not the more usual 12x24". This means we won't be able to do it on Ponoko's service at the full size, but I should be able to lay it out for 12x24 for most laser cutters.

Scores: on this one, most folds were fine, but the ones shown in the lead image are folded much further -- 180 degrees instead of 90. So I think reinforcing them with tape OR doing a different kind of seam, like a dotted seam, would be best.

I know @pablo has lasercut this before -- have other folks attempted this? Any tips or design files to share?

Update: looks like these files won't fit all on a single 12x24" sheet -- see:


That's too bad! It'll have to be printed on two separate sheets for many laser printers.


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8 Comments

Hi, @pablo - thought you might have thoughts on this, or maybe even design files to share?


I had posted the .ai file I used to cut, and I've just uploaded the original .svg, as I am not able to open that .ai (check the research note https://publiclab.org/notes/pablo/11-09-2016/how-to-do-upgrade-desktop-spectrometer-kit-2-0-to-the-version-3-0?_=1487194384). They are just the the same original vectors but removed some duplicated paths from the original file in the spectrometer repository. I just made a test and I think it does fit in 15x15 inches: lasercut-ponoko-pablo-15x15.svg

Regarding scores: I think it is a question of the power of the laser (or whatever indicator used to limit the strength of the cut) and the cardboard. Tuni, the guy who laser cut it for me, knew the power for that particular type of cardboard. Reinforcing it with tape I guess is another good way to go.


Hey @warren, I made a test and it does fit in a 12x24 inches board. See my file: lasercut-spectrometer-3.0-12x24.svg

Note, funny for my to talk in inches!


Hmm, interesting -- but are you sure the one you made wasn't mini as well? The Ponoko one I cut ended up almost exactly 19 cm long when assembled. Can you check if yours is full sized?


Mmmm, weird! The one I lasercut is 23.5cm long, as it should. I just measured it.

However, all the files I am looking now in inkscape (the ones I just downloaded from github and the files I modified and sent for print) are around 19cm long. I'll keep looking to see what I am missing.

If you can, try to open the file (https://publiclab.org/system/images/photos/000/018/857/original/spec-cut-clean-plainF_archivo-final-corte.ai) they used for lasercut and see its lenght!


Reviewing the original .svg files I see they have the size in pixels defined, not in inches or cm. So it makes the standard conversion.

Before version 0.91 inkscape converted 1 inch to 90px and viceversa. Then it converted 1 inch to 96px.

It looks like those files were made with Adobe illustrator that used an Inkscape version 0.48.3.1 ("<!-- Generator: Adobe Illustrator 16.0.0, SVG Export Plug-In . SVG Version: 6.00 Build 0)").

So, when we open those files in Inkscape it has to convert the pixels to inches or cm, and it uses that conversion. That's why the length of the box, which measures 670px if you see it in inkscape, is "translated" to cm as 18,9cm, exactly what you calculate using the 90px per inch (670 px/ 90 inch = 7,4 inch = 18.9 cm).

I use a version 0.91 Inkscape, but it seems that it uses the conversion 1 inch = 90 px.

I think the problem might be related to that.

Reference: http://wiki.inkscape.org/wiki/index.php/Units_In_Inkscape


The files at https://github.com/publiclab/spectrometer3/blob/master/spec3-pdf.zip when opened in inkscape gives the correct size.


Thank you Pablo for investigating this! Very helpful.


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