Wednesday, February 3, 2010

Rapid Prototyping

There's a lot of ground that's covered by the umbrella term of 'rapid prototyping,' but one aspect that's conceptually straightforward is usually a pain to tackle. Having a solution in-hand, I'm excited to share it.

Q. How do I convert from my CAD format to a DXF so that I can cut out my circuit on a laser cutter or cutting plotter?

Why would you ever want to do this? Well, perhapse you sent out some PCB files to be manufactured and wanted to cut your own mylar solder-paste stencils on a laser cutter. Possibly you're making your own flex-circuits at home out of aluminum foil and contact paper (if you don't have a cutting plotter you could always use an iron-on transfer, an X-acto knife, an inkjet printer and some really steady hands). Maybe you wanted to clone all of your drill hole placement and so that you could make a jig to use with your drill press. Some artist came by your lab and thought that your high-speed impedance-matched data bus would look super futuristic if it were water-jet cut out of sheet titanium and sold to fashionistas as jewelry. Or you think the Arduino layout would make a really awesome graffiti stencil (if only you could loss-lessly scale it up 50x and cut it out of plastic). Lots of applications require getting your CAD layout into some non-CAD format, and preferably a vector format. So, now that you have the 'why', here's the 'how'.

A. You'll need your CAD software, a decent print manager and Adobe Illustrator or equivalent software.
  1. Starting with your layout - select-to-display only those features of the layout that you want to "print". Then print your file (non-scaled) to PostScript (.ps).
  2. Open your PostScript (.ps) file with Adobe Illustrator. At this point, all of your 'traces' will be 'lines', aka 'strokes' with a defined width, which you don't want. You want an actual closed 'outline'/path that describes where the laser/knife should be applied by your relevant plotter.
  3. Delete any features (like origin markings) that you don't want and Object -> Group the ones that remain.
  4. Then copy what's left into a new layer (for safety). AKA: Select -> All; Edit -> Copy; Window -> Layers -> New Layer; Edit -> Paste
  5. Make the original layer invisible, so as not to muck with it.
  6. Select -> All ; Object -> Path -> Outline Stroke
  7. Object -> Expand
  8. Window -> Pathfinder
  9. And then in the Pathfinder window (have everything selected), click on 'Unite' and then Option-click on your selected object.
  10. Export your file to DXF using File -> Export.
  11. BAM!

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