Engraving With Sunbeams
Inspired by all the usual experiments one might do as a kid with a magnifying glass and some sunlight, Instructables user rabbitcreek decided to make his own engraving machine.
Powered by an Adafruit Feather 32u4 Basic Proto, he uses a couple of stepper motors to move the project piece around, and a servo to operate the shutter. To focus the sun's rays onto the work, he uses a large premium grade Fresnel Lens.
When first powering up the machine, the focused rays were so powerful that they just set the work on fire. To mitigate this somewhat, he devised a couple of plans. The first was to cover up a large portion of the lens with removable velcro. The second was to include a shutter, so that the beam was not hitting the work when the gantry wasn't moving. Originally, there was a plan to build a system that would allow the machine to auto-track and follow the sun, but it worked out a lot simpler to just adjust the machine manually every 10 minutes.