Solar CNC Burns with the Sun's Rays

Using a small mirror, it’s possible to focus the power of the sun to burn a small area. For better or worse, lots of kids quickly try this experiment and generally move on.

If it’s possible to burn one point, it’s therefore possible to burn lots of points, or even lines; even a whole sketch could be made with the proper amount of patience and control. Apparently not wanting to do this by hand, YouTuber Cranktown City created a CNC “laser” machine that automatically engraves with the power of the sun.

As shown in the video below, the machine build starts off with a fairly conventional CNC gantry setup: linear rails plus stepper motors, allowing the workpiece to travel in an X/Y plane. An overhead arm holds a lens in place in order to burn the area underneath for burning. Since the sun moves across the sky during the day, this sort of setup isn’t quite enough to properly catch the sun’s rays for more than a short time, meaning yet another set of axes had to be added underneath the CNC for tracking.

Here Cranktown used a pair of windshield wiper motors to tilt the machine, along with an LDR setup borrowed from a GreatScott! project, previously featured here. An Arduino Uno reads LDR intensities, and depending on the results closes contacts in an H-bridge relay setup to activate the motors. With the focusing lens, and a bit of CNC up-down-left-right, it’s able to create drawings. Potential future ideas include a better lens or even a shutter, but for now it’s quite a neat and functional proof of concept.