Most IEEE Spectrum readers are well aware of the declining cost of 3-D printers. Still, if you don't have the scratch for a US $15 000 desktop unit or the time to build yourself a RepRap, as Paul Wallich described in our January 2009 issue, you'll probably find owning your own unit out of the question. But as Wallich suggested in these pages in September 2010, there's a third avenue to 3-D printing that's easier and probably better: Shop out the work.
Those words may be anathema to hard-core do-it-yourselfers. To be sure, your fingernails will stay embarrassingly clean—the only tools you'll be picking up are calipers and some computer-aided design (CAD) software—but turning an idea into a physical object this way still involves some hands-on moxie, as I've recently discovered.
The abstract interest I had in 3-D printing became quite concrete when I needed an enclosure for a microcontroller. The one I was using—an Arduino Pro Mini from Sparkfun Electronics—is tiny and lacks screw holes, so there was no built-in way to mount it.
To start, I needed to acquire a serious 3-D CAD package. My first choice would have been SolidWorks—the software of choice for many mechanical engineers. But (ouch) licenses start at about $4000. While I'm sure the program is duly impressive, it's overkill for an occasional user like me. Lots of CAD software is available free for the downloading, but the ones I've tested proved far too crude for a project like this. So at a friend's suggestion, I acquired what appears to be the perfect Goldilocks solution: Alibre Design Personal Edition, which is plenty powerful enough for my needs without inducing sticker shock. It costs just $99.
It took me some time to get comfortable with the user interface, because rather than specifying the dimensions when you first draw something, you instead create only a very approximate shape. Then you add dimensions or constraints, at which point the program changes the shape to match whatever specs you set.
It also took me a while (and a visit to Alibre's online forum) to discover the real key to using the software—literally: the F5 key. Hitting F5 regenerates the object on screen with whatever changes you've lately made to its specifications.
Because the Arduino Pro Mini is so small, I decided to mate it with Sparkfun's matching prototyping board, which fits within the same tiny footprint. This would give me a place to mount connectors to the microcontroller, along with a few discrete components if need be. The prototyping board sits directly above the microcontroller, so the whole package remains quite compact.