Laser cutting / CNC milling marine plywood

Discussion in 'Boatbuilding' started by laukejas, Nov 20, 2019.

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Laser cutting or CNC milling?

  1. Laser cutting

    0 vote(s)
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  2. CNC milling

    100.0%
  1. laukejas
    Joined: Feb 2012
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    Location: Lithuania

    laukejas Senior Member

    Hi,

    I have another ambitious project for the next summer. I am designing a plywood sailboat which will have a lot of precision joints (puzzle joints, finger joints, mortises, etc.) to help strength and alignment, as well as saving the time and effort during the construction. However, this design choice means that the multitude of plywood parts will have very complex shapes and features (slots, cut-outs, etc.) that have be cut very accurately in order to fit together. Plotting and cutting it by hand (even with a jigsaw) is nearly impossible to achieve the necessary precision. I am thinking of either laser cutting or CNC milling.

    My first choice would be laser cutting, because it is less limited in what it can do (very small holes, inner 90° corners, etc.), and is a lot cheaper. I have consulted with various firms around my country that have CO2 laser cutters, and tables large enough for full-sized plywood sheets. None of them have any experience cutting marine plywood, because it's a quite new thing in my country. I have been advised, however, that the waterproof glues used in marine plywood may not play well with laser, and that it tends to burn.

    I have access to a 40 watt laser cutter, which can cut through 9mm of birch plywood, but I when I tested it with marine plywood, it barely managed to cut through 4mm (5/32") BS1088 okoume plywood, which is what I will be using for this boat. This laser scorched it quite a bit, because I had to go slow in order to cut through at all, so I am not sure if a more powerful laser would do a better job. The industrial lasers that I inquired about are anywhere from 500 to 2500 watts, so I'm pretty sure they should cut through 4mm marine ply... But they might still burn it. Or not.

    So, have any of you had any experience cutting marine plywood with laser cutters? Is it at all doable? What kind of result can I expect?
    Also, very importantly, how well does epoxy stick to the laser-burned edges of plywood compared to traditionally cut edges? A lot of my joints will rely to epoxy sticking to these edges, and it being able to seal them from water ingress.

    If laser cutting turns out to be impossible or impractical, I will have to resort to CNC milling. I don't really want to do it, because it's expensive, has limitations I mentioned above, and has a certain chance of failing (small parts flying off and ruining everything).

    I looked into Chesapeake Light Craft, which are selling boat kits with pre-fabricated plywood parts, and I found pictures of both laser-cut and CNC-milled kits, but I am not sure what kind of plywood they were using in each case.

    So, laser cutting or CNC milling? Can someone offer any insight?
     
  2. latestarter
    Joined: Jul 2010
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    Location: N.W. England

    latestarter Senior Member

    I looked into laser cutting 4mm marine plywood about 10 years ago, decided against it. As well as scorching/burning it can create very toxic fumes.
     
  3. laukejas
    Joined: Feb 2012
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    Location: Lithuania

    laukejas Senior Member

    What kind of laser produced such bad results? How powerful was it?
     
  4. latestarter
    Joined: Jul 2010
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    Location: N.W. England

    latestarter Senior Member

    No idea, I visited the company, was not impressed with their samples, may have been an older machine.
     
  5. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    We have cut a fair amount of plywood with laser. The lens tends to get dirty pretty fast and needs continuous cleaning. Compared to a router, it is very slow. Also, the edge gets tar/carbon buildup which would need to be sanded clean for gluing. I don't know what kind of deterioration, if any, happens to the glue with the high temperature of a laser.
     

  6. DCockey
    Joined: Oct 2009
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    Location: Midcoast Maine

    DCockey Senior Member

    My impression, and only an impression, is laser cutting is frequently used with very thin plywood such as used in model kits. A guess is the speed of cutting with laser is inversely proportional to the thickness of the material.
     
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