A Poor-Man’s Laser CNC Engraver

What do you get when you mix the disappointment that sometimes accompanies cheap Chinese electronics with the childhood fascination of torturing insects with a magnifying glass on a sunny day? You get a solar-powered CNC etcher, that’s what.

We all remember the days of focussing the sun on a hapless insect, or perhaps less sadistically on a green plastic army man or just a hunk of dry wood. The wonder that accompanied that intense white spot instantly charring the wood and releasing wisps of smoke stayed with you forever, as seemingly did the green spots in your vision. [drum303] remembered those days and used them to assuage his buyer’s remorse when the laser module on his brand new CNC engraver crapped out after the first 10 minutes. A cheap magnifying glass mounted to the laser holder and a sunny day, and he don’t need no stinkin’ lasers! The speed needs to be set to a super slow — 100mm per minute — and there’s the problem of tracking the sun, but the results are far finer than any of our childhood solar-artistic attempts ever were.

Do we have the makings of a possible performance art piece here? A large outdoor gantry with a big Fresnel lens that could etch a design onto a large piece of plywood would be a pretty boss beachside attraction. Of course, you’d need a simple solar tracker to keep things in focus.

45 thoughts on “A Poor-Man’s Laser CNC Engraver

    1. ya know i’ve allays had a problem with calling the reaction inside the sun thermonuclear.
      yes theirs heat and theirs some thermonuclear elements to it but it’s more off a gravity and pressure driven reaction

      plus it’s fusion not fission witch is more commonly refers to thermonuclear

      1. Thermonuclear is apt since most of the energy output of our sun is due to hydrogen fusion.
        The process is driven by the nuclear forces and quantum interactions, gravity simply provides containment.

        1. Indeed.

          The term thermonuclear is used exclusively to refer fusion. Usually fusion of light elements such as hydrogen but can also refer to the Carbon-Nitrogen-Oxygen cycle. Also known as the Bethe cycle after Hans Bethe.

  1. this is awesome.

    @Saabman you won the naming contest

    would it be possible to use fiberoptics to transmit the sunlight from a separate collector?, it would mean one could use vastly more power without scaling up the gantry, plus one could use it indoors and have the collector outside.
    it should also simplify any tracking required, since one wouldn’t need to haul around the gantry and workpiece.

    1. Maybe add an LDR or solar cell to track the brightness and automatically adjust the translation speed. Maybe a pinhole camera style sensor with say nine light sensors in the back to automatically track the light source without any software.

      1. The pinhole tracker method is what I had planned to use in the mechanism described below using an az-el mount driven with surplus geared DC motors (stepper motor accuracy not necessary) to adjust the position of all hardware involved meaning everything should be as light weight as possible and the mount rigid to avoid vibration in any wind. This movement could also be done manually unless the solar etching process was too slow and the unit must be left unattended. BTW, this was all planned prior to the common availability of cheap micro-controller hardware.

        A retro way of doing this would be to mount a photo on a shaded half of the same drum used for the wood veneer (as described below) and have a photodiode or phototransistor “read” the photo which would then be reproduced via solar etching on the veneer.

        1. In the retro method, light level into the lens would be adjusted with a simple iris mechanism to adjust the darkness of the burn and to compensate for cloud obscuration.

        1. I’ll take your word for that :)

          Seriously, ‘raw’ sunlight is a bit different from an nd:YAG laser which have a very ‘narrow band’ monochromatic output and are usually operated in ‘pulsed’ mode.

      1. I suspect that Duty Cycle has a *lot* to do with things involving fiber optics & lasers.
        My google-fu is poor today. I tried to find a relevant link, but kept hitting paywalls & keyword aggregators.

        1. I’m sorry to see that I’m not the only one disappointed with the quality of Google searches lately. Half my results are paywalls, or even worse, fake PDF documents that *contain* Google search results. What’s up with that? My guess is to drag in a few pennys of advertising revenue from Google.
          The other half are fake results for hard to find equipment manuals, which are nothing more than a con-job to lure you into downloading their “special” reader ap (malware in disguise).

    2. >would it be possible to use fiberoptics to transmit the sunlight from a separate collector?

      Maybe.

      This is the subject of a lot of work in solar energy – reducing costs by focusing the sun on a single, small, high-power cell rather than a broad field of the usual ones. Results are mixed.

      Light pipes as you describe are also used in some intriguing (and often beautiful) architectural features to provide interior room light sourced from collectors on the roof, but the power carrying capability of the fibers is a limiting factor.

      1. Light pipes in buildings aren’t fibre though – at least ours isn’t. Ours is a ~1 foot wide tube of very reflective aluminium foil or similar. Works a treat, and extremely simple, no need to focus it onto a fibre or diffuse it back out to a sensible size for lighting.

        1. There are some solar collectors out there that look like satellite dishes, but they’re not far along in development yet. I’m getting off topic here, but, we’ll probably start to see something like light pipes with adjustable (manual or automatic) reflectors coming onto the market soon to improve light pipes.

    1. Was gonna mention that. 3D printing with a big contraption and some Fresnel lenses. The electronics are solar powered too. Works best in the desert, which fortunately gives a large supply of free sand.

  2. Ok before i read the article past the title and such. this is the image that popped into my head.

    BIIIG magnifier lens. robotic arm … Sun. … Ant pile.

    Robotic ant annihilator Deluxe. When your just to busy to fry those darn ants.

    1. Gut an old projection big screen or order a similarly sized fresnel lens and you won’t need a complex arm, just a simply tracker. The focus should be a few inches in diameter, enough to bake the whole mound Bond villain style. Even a rough focus should be a couple hundred degrees.

      1. I got one of those, but it was for a triple crt projector rear screen TV. The Fresnel lens has 3 focal points making it useless for this task. The worse news is that cockroaches really liked being in there. Net cost of ‘free’ TV was negative.

  3. That’s literally the coolest thing I’ve seen in ages. Super super super clever I’m jealous that I:

    (A) didn’t come up with the idea
    (B) don’t have the chops to build if if I did

    Congrats

  4. Many years ago, I thought of doing something similar, but using a stepper motor controlled drum with removable wood veneer wrapped around it it and the lens mounted to and moved with a transverse screw mechanism also driven by a stepper motor. An IR diode would be used to sense sunlight IR level to adjust for cloud obscuration and that info used to adjust spot beam movement speed.

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