Lasercutting foray

I’m playing with doing some lasercutting, using Ponoko and their Inkscape starter kit to do the cutting. I gave myself just a few hours to prepare a single test file to send off for fabrication, just to get my feet wet. First time using Inkscape, and first time in over 10 years to try to drive a laser cutter.

Inkscape is sadness on a Mac. It runs in X11 which is mostly intolerable. It’s unaware of the Mac file system. But the worst thing is the rendering is just really ugly. It’s a shame there’s no Cocoa native port of Inkscape, although realistically that’d be a lot of work to do right. BTW is it just me or if you copy a path from one Inkscape window and paste it to another, does it get converted to a bitmap?! I had to save the thing to a file and then import it to preserve the vector data.

Ponoko’s use of Inkscape is quite simple. Basically just make a bunch of blue lines 0.01mm wide for cuts. Some extra options for engraving, fills, etc. I made some circles and an outline of my name in Futura as test objects. But on to the more interesting things.

First, my walks tracks. Converting my complex walk shape to a cuttable SVG was not easy. The GPS tracks themselves are not sensibly cuttable, of course, you’d end up with confetti in the middle. What I want is to cut the concave hull of my shape, plus do something clever to depict some internal structure. Not sure how to do that. Even concave hull isn’t easy; ST_ConcaveHull isn’t available until PostGIS 2.0 which I’m not yet using. So what I did was use a combination of QGIS and Inkscape to make a filled shape of all my walks, a raster blob, then use Inkscape’s bitmap tracer to turn that into an outline path. Even then I got kind of a mess, had to go in and remove a lot of points. I’ve still got a disjoint lobe in my object which is going to screw up the cut, but I left it in there because I was curious what would happen and I don’t know how to easily fix it anyway.

Second the San Francisco Bravo airspace. This was pretty straightforward; load up the shapefile from FADDS in QGIS, print it to SVG, done! Well almost; that results in a bunch of lines being double-drawn, which causes the laser to cut twice. Ponoko doesn’t want you to do that and has instructions on how to manually break up shapes so duplicate lines don’t print. I did my best but I probably missed some spots.

OK, my SVG file is done, ready to cut! Now then, what material? Ponoko has a fun variety of options. Cardboard would be the natural cheap material for testing, but it’s kind of flimsy for some of the fine angles and they recommend not using the raster engraving option, which I’d already done as test images. I went with cardstock on the theory it’d be most forgiving to any materials / delicacy problems.

Some sample prices for my relatively simple object, 7.1″ square material sheet. Prices are “making”, which I take to be laser time, and then the material.

  • Cardstock: $7.13 + $2.36.
  • Thin cardboard: $7.93 + $0.23.
  • Cherry veneer MDF: $14.83 + $4.34.
  • Fluorescent orange acrylic: $8.27 + $3.72.
  • Bamboo: $8.27 + $2.82.

$10 for the item and another $10 for shipping and the order is in! They say it takes “typically 1-2 weeks”, but I see there’s a design review first which will presumably take some time on their end and maybe mine.


2 thoughts on “Lasercutting foray

  1. Regarding the Inkscape rasterization thing: I’m by no means an accomplished user, but I’ve been using Inkscape recently as best as I’ve been able to manage to get some various vector work done. I was confounded by the same problem you mention. Fortunately, some googlage revealed a simple fix (though I’m not at my work computer now so I can’t verify). If I recall, it involved turning off a pref within the X11 app itself (not Inkscape) pertaining to pasteboard/clipboard synchronization between X and the Mac OS. With that off, vectors finally stayed vectors when copied/pasted within Inkscape.


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