No-Laser CNC Engraver Is Something New Under The Sun

Hooking up a laser to a CNC gantry isn’t exactly an Earth-shattering innovation, but it does make for a useful tool. Even a cheap diode laser mounted to an old 3D printer can do engraving, marking, or even light-duty cutting. But what about a laser engraver without the laser? Can that be of any use?

Apparently, the answer is yes, if you can harness the power of the sun. That’s what [Lucas] did with his solar-tracking CNC engraver, the build of which is shown in the video below. The idea is pretty simple — mount a decent-sized magnifying lens where the laser optics would normally go on a laser engraver, and point the thing at the sun. But as usual, the devil is in the details. The sun has a nasty habit of moving across the sky during the day, or at least appearing to, so [Lucas] has to add a couple of extra degrees of freedom to a regular X-Y CNC rig to track the sun. His tracking sensor is simplicity itself — four CdS photocells arranged with a pair of perpendicular shades, and an Arduino to drive the gimbals in the correct direction to keep all four sensors equally illuminated. He had some initial problems getting the jerkiness out of the control loop, but the tracker eventually kept the whole thing pointing right at the Sun.

So how does it work? Not bad, actually — [Lucas] managed to burn some pretty detailed designs into a piece of wood using just the sun. He mentions adding a shutter to douse the cutting beam to allow raster patterns, but even better might be a servo-controlled iris diaphragm to modulate beam intensity and control for varying sun conditions. He might also check out this solar engraver we covered previously for some more ideas, too.

Thanks to [Zane Atkins] for the tip.

28 thoughts on “No-Laser CNC Engraver Is Something New Under The Sun

  1. I have an imagination of a robot with diggers and solar sintering that goes on to a plat of sand (beach, desert, etc.) and autonomously digs, stacks and sinters a glass walled building with only solar power needed and construction materials consisting only of local sand. It could run every day for maybe months or years depending on the project size.
    Or maybe build a really big one and take another crack at building a bigger pyramid in Egypt. Make it from sintered glass in layers like a 3d printer with angle supports and access pathways inside, etc. and a filler of sand.
    When the next scientists discover it as a future antiquity they will be amazed.

  2. If you are not in a hurry, perhaps instead of fighting the sun’s (apparent) movement, you could use it as one axis of motion. And if you are really not in a hurry, the yearly movement of the sun could be the second axis.

  3. Pretty cool. I wonder how hot you can get a small sample? It has a severe limit on dot size compared to a laser so you can’t do detailed work. But that is just a matter of size and viewing distance. (You only need one deg of freedom to track the Sun. If the spot could be arbitrarily small you would track at a slightly different angle.)

    How about a variation on the old solar insolation recorders that burned a spot on a paper drum? Do a vertical up-down scan at a good speed to get nice variation in color between overcast and clear and run it all day. I know from testing those kinds of trackers that they track the the part of the sky with the most light and work OK with clouds. With the steppers a clock drive should be easy and forget about the tracker.

    1. Well it wouldn’t hard to improve the optics for a more focused spot, but I wonder if you would not be better off with a big suncatching dish focusing the sun on a lasing material in a ‘normal’ laser setup – just replacing the flash bulb with a large area of sunlight collection.

      Then you get control of the output wavelength, and a much tighter beam that would be easier to focus down to tiny spotsizes no matter how the sun moves – all the sun moving is going to do is probably change the power output a little.

      1. Optics won’t help the spot size unless you start with really bad lenses. It is the extended source of the Sun that puts the limit. You can get a smaller spot size from Mars :-)

          1. How so? Shorter focal length/wide angle can give a smaller spot, but the smallest focus is always an image of the Sun. With a point source you cab get an arbitrarily small focus spot. But the Sun has the apparent size of the full Moon. It is a big fat source.

          2. The point is you can use multiple lens to get the effect you want in more compact form, with swings and roundabouts in things like light capture area vs the single lens that creates the spot size you want at the distance you want it.

          3. Without excessively expensive optics, it is hard to go much shorter focal length than the effective lens aperture. The only remaining solution to reduce the spot size is to only collect from a small region of the sun. Obviously this means much less power, but as Foldi-one says the lens can get bigger, especially if a reflector is used, so this is feasible. The downside is the diaphragm used will be dissipating most of the power, and it would complicate the optics further to make this happen at large scale… So it is going to get *hot*

  4. Not everybody can afford a 3D printer, much less having an old one laying around! I admire the project, he’s doing a great job but I wish I had even a cheap 3D printer…

      1. My makerspace got rid of all the 3D printers, no one was using them, they did all their 3D printing at home. This is because 3D prints take so long, and you had to stay at the space the whole print time for safety reasons. So, everyone just got a 3D printer at home. My point is that those printers had to go somewhere, I didn’t ask where, but I imagine they were sold to people to use at home, probably at good prices, so check out your nearest makerspace and see if they have any for sale.

  5. Casually, my classmate Pedro Chana and I made something very similar during our Fabcacademy course at Universidad Europea de Madrid. We called it “Solaser”. It uses a fresnell lens, and we got a pretty good velocity engraving playwood (10 mm / sec). So fast we discovered we didn’t need solar tracking. You can find it here, along a very detailed documentation in case anyone wants to do it:

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