I wanted a way to be able to pre-visualize something before I cut it out on the lasercutter or CNC, so I came up with a new invention I call the PHOTOolbit™, a photonic toolbit that traces out the pattern that will be cut.
You can make one quite easily, and it will allow you to capture photographically the toolpath and even animate it so you can quickly see how a piece will be made.
I've found it useful because it shows the toolpath in-situ on the machine so I can see, for example, if its going to run off the edge of the workpiece, and it gives me a better idea seeing it at true 1:1 scale than just looking at the computer screen.
I sometimes plug in my Metaglasses so I can see it as an augmented reality overlay.
This opens up the field of "Computational Lightpainting" (abakography) to the world of CAD.
The first step is to make a photonic toolbit.
For the laser cutter, I machined down a piece of metal the same shape as the focusing unit, so it snaps in place magnetically. Upon the front upward-facing side I attached two LEDs, and later a multicolor LED.
The LEDs are driven by a small microcontroller.
The microcontroller is fed by a photodiode that picks up the light reflected from the laser shining on the workpiece.
The microcontroller is programmed to respond to the light from the laser cutter (infrared) and to provide a corresponding visual display.
Alternatively you can use the simple analog amplifier of my previous Instructable (see the figures on Step 3 of that previous Instructable).
In this way, whenever the laser comes on, the LED starts glowing.
I often have it glow one color for traverses, a different color for etching (raster), and yet another color for cutting.
For the Shopbot, I made a piece that goes in the spindle.
A standard 1/2 inch wooden dowel works good.
Sharpen the end of the dowel just a bit (keep it nice and dull but put a bit of a taper on it with a pencil sharpener).
Cut it off and mount your light.
Experiment with various configurations.
First try having the light on all the time.
Try a light bulb and try some LEDs.
Then try connecting the light to an amplifier and feeding the input of the amplifier from some process of the machine, such as motor current, sound, light, etc..
Experiment with different phenomenological quantities until you find the results you want.