Solar-powered CNC woodburning

[Johnie] built himself a CNC woodburner powered by the sun. Like the solar 3D printer we saw last summer, [Johnie]‘s build uses a giant Fresnel lens to focus sunlight onto a piece of wood. To get some control out of his build, a 2-axis bed was made from scrounged and junked parts.

The lens in [Johnie]‘s build looks to be about a foot square – more than hot enough to burn a few holes in things from our experience. The bed (hopefully) gets around this problem by being built entirely out of clear acrylic. The idea behind the acrylic bed is that the focused light will pass through harmlessly, and not melt the entire thing.

Now that we think about it, we couldn’t come up with a better project to enter in the Buildlounge laser cutter contest. For everybody else working on their laser cutter projects, the deadline is January 1st. Better get those wrenches out and irons hot, because we’ve seen a few awesome projects for the Buildlounge build off already.

Comments

  1. insapio says:

    THIS is exactly what I needed to find. Now I just need to find a fresnel lens…

    Also, with a large solar panel, this could be made completely solar powered.

    • Hirudinea says:

      Yea, thats what I thought, the title is “Solar-powered CNC woodburning”, I expected all solar power, well he could use rechargeable batteries refilled with a solar charger.

      @ John C – For the “solar power” monitor he could use an IR Thermometer aimed at the focal point of the lense, when the temp drops cut the motors.

    • Trebu says:

      You can find a fresnel lens in an overhead projector.
      You can pick up a used one at your local university’s Reuse Center. I bought one for about $10, but it did need a new bulb.

      http://www.facm.umn.edu/about/central-services/reuse/

    • Johnie Sublett says:

      Rear-Projection TVs have fresnel lenses in the screens, but the two I recycled (a 50 and 60 inch) had milky lenses. Big, but not very powerful. You might have better luck with a projector lens or even a book magnifier like I used. Both are powerful enough to melt rocks, glass, pennies.

  2. Can you please, please, reshoot the photo with an action figure in the center as the sun beam focuses at his crotch.

    Caption:
    No bond, I expect you to tie.. Muwhahahahaa

    Seriously sweet.. Gets around the whole, need a big freaking laser to cut stuff.

  3. ChalkBored says:

    The next step is….
    Sharks with frickin fresnel lenses attached to their heads!

  4. GaspingSpark says:

    Acrylic is opaque in much of the infrared spectrum. It could still take a lot of damage from focused sunlight. Unless of course the fresnel lens itself is thick acrylic and it filters those bands already. That’s why you never mount an infrared heat sensor behind acrylic. For fun find an infrared heat source like a fire and hold up a piece of acrylic in front of you – you’ll notice a significant reduction in radiant heat behind the acrylic.

    • Eirinn says:

      Very informative! Although i don’t think a fire is a very good example. Hiding behind anything near flames is likely to drastically reduce the heat radiation ;)

    • Johnie Sublett says:

      Hmm. Well I did focus the Fresnel lens on the acrylic table for a minute or two and all it did was oxidize a brown spot on the surface. Held up much better than I expected. Although I picked acrylic mostly because there was lots of scraps of it in my High School’s shop class, which recently became the engineering shop room.

  5. jethomson says:

    Hey, I’m in this contest too. Can’t I get some love? Hack a T-qualizer Inverter to Make a Musically Animated EL Wire Display

  6. John C. says:

    Awesome project – makes me want to finish my solar cooker :)

    Just a couple thoughts…
    * create a “solar-power” monitor – tie it to the speed of the material movement, slowing (or stopping) when a cloud obfuscates the sun. The speed could be relative to the amount of measured sunlight.

    * create a table that can map each material to the speed it would move

    * it’s difficult to tell if you’re doing this already but: when finished with one character and moving to the next, have the speed of the motors set to maximum. (this would minimize the amount of inter-letter burn)

    .

    • Johnie Sublett says:

      These are all great ideas. If I ever rebuilt this project, I would probably incorporate all of these ideas. I originally wanted to use stepper motors for this, but had to settle for geared motors (I asked my high school PLTW Digital electronics teacher if I could borrow some steppers and he tried to hand me broken servos…). I also only had a week to build it for the Avnet Project originally, and I’d never used a micro-controller before. So now I can admit that the device has one motor speed – on – which is why the multiple tracings are needed. The x table even moves slower than the y table because of the extra weight. It was really more of a proof-of-concept learning experience than a functional tool. Good luck on your solar cooker.

  7. Ramsay says:

    Perhaps a cool addition to this would be a short 3rd axis to move the workpiece in and out of focus? My limited experience as a child suggests that just dropping it 5-10mm should mean that you are not sufficiently focussed to burn? Then you can move between cuts and raise it back up to the focal point to begin burning again…

    • Johnie Sublett says:

      That would be a great addition. It would also allow me to make larger works, because right now I’m limited to how long the sun stays in focus for burning. It would have to move quickly though, as to not burn the area as it refocuses. And you are correct about the focal length. It’s the main reason I had to build such a positionable stand.

  8. zuul says:

    He already won the avenet contest with that

  9. You can get giant fresnel lenses from old projection TVs. I picked a 50″ one out of a TV left out on the curb.

  10. Johnie Sublett says:

    Thanks for all of the great feedback guys. I’m glad you liked my work. I was wondering why my video went from 26 to over 1k views all of a sudden. I’ll try to answer any questions or comments. And if you really like the project feel free to vote for it at buildlounge.com Now I’ve got to get back to studying for High School…
    Cheers!

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