Author: Matt Bell / Source: Make: DIY Projects and Ideas for Makers
For Maker Faire Kansas City this year I wanted to make a drone racetrack for micro FPV quads. Normally these courses consist of lots of LED-lit circles for the quads to fly through. I wanted to make something a bit more sculptural and ambitious: giant spider robots mining a floating asteroid field.
To keep costs down, and because it’s generally an awesome building material, I decided to use cardboard for everything. My new laser cutter had just arrived and I figured I’d use it to do all the cutting.
But a problem arose. I wanted to make these giant cardboard asteroids 4 to 6 feet in diameter, and the pieces were just too big for my little laser cutter. I needed another way to make them.
The approach I decided on was to create 3D models of my asteroids and then use a digital projector to project the individual polygons onto big sheets of cardboard so that I could use an ordinary tool to actually cut them out.
Possessing the superpower that is knowledge of software development, I decided to make — and share — my own little program to make this process possible. It’s called PolyProjector. If you want use it to make giant cardboard forms of your own, I have some tips for you.
You can save up Amazon boxes, ask at the grocery store, or heaven forbid actually buy it, but the best way I know to get a ton of good cardboard is to go to a neighborhood recycling center.
The ones I’ve been to have giant walk-in shipping containers filled with as much clean, stacked cardboard as you could want. Not just little stuff either — they’ve got the big boxes that refrigerators and couches come in. Just be sure that when you’re pulling out cardboard you don’t make a mess. Leave the place tidy.
You’ll probably want to get a consistent thickness of cardboard. It turns out there’s a huge variety of the stuff: lightweight, heavy duty, single ply, double ply, I even ran into stuff that was four layers thick. You can mix and match without too much trouble; you’ll just have to adjust on the fly during assembly.
2. Preparing the 3D file
The program I wrote accepts OBJ files (sorry, no STL). My program expects the units of the file to be in meters. If you need to convert files from another format or change the scale, I’d suggest checking out Blender. It’s free, can import many file types, can export OBJs, and works on just about any type of computer.
3. Projector setup
Set up your projector so that it points down at a horizontal work surface and covers enough area to project the biggest of your pieces, while still giving you plenty of wiggle room to work. You’ll have to do a bit of MacGyvering to get it in the right spot. My solution was to cut a rectangular plate out of plywood, bolt the projector to it using the mounting holes under the projector, then hang the whole thing from pegboard in my shop. Whatever technique you use, double-check that your mounting is secure (so you don’t have…
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