Piles Of Foam With A Hot Wire Slicer


There are a million things you can do with foam, from some very impressive RC airplanes, all the way up to full-scale planes you can fly off into the wild blue yonder. Cutting foam, though, that’s a problem, and your best option is usually a hot wire foam cutter. [Darcy] put up some plans for a very nice bow cutter, but there’s also some experimentation for a foam slicer – a hot wire machine that takes a foam part and slices it like a smokehouse ham.

The bow-style cutter features laser cut parts, a pair of 1/4-20 bolts, a power supply, and about a foot of nichrome wire. It’s the bare minimum for cutting foam, but it seems to work really, really well.

The hot wire foam slicer is a much more interesting contraption, capable of making multiple thin sheets out of foam. Basically, it’s a laser cut tray with a bolt hole pattern running along the sides. Put two bolts along the side, loop some nichrome wire around the screw flights, and you have a way to cut foam in thicknesses of about 1/20th of an inch. Great if you’re trying to skin a model in very thin depron, or you just can’t find the right thickness of foam for your project.

23 thoughts on “Piles Of Foam With A Hot Wire Slicer

    1. In my case it’s not about sawing or cutting material by hand, be it a sheet of plywood or a foamboard, but rather transferring the design onto the surface. Let’s take Flite Test’s fomies’ and think how one can get one flying.

      1. Print the tiled version of design files. 8×11″ fits quite well on A4 but there are no guidelines to make the tiles fit perfectly. It takes me an hour or two to stitch those well enough. With plans stitched together at hand you need to sit down and carefully trace them, the next two hours (I assume a trained hacker can divide thie times by two). You’ll never get a millimetre accuracy. Price in money: negligible.

      2. Go to a printing shop and have the plans printed on A0 sheet. Now stitching, two hours less. There is a chance of getting the final parts 1-2 millimetre accurate. Price in money: 3 €.

      3. Go to a printing shop which has a laser cutter (the one near me has a machine a working area 70×40 cm, if I take a bus the other can cut 120×80 cm) pay 8 € and have your design cut for you exactly how it is supposed to be. The only drawback is that you probably would have to collect the parts the next day.

      Conclusion: unless one takes their hacker’s pleasure from the very cutting, I recommend handing the job to people and machines that do it better.

      1. Conclusion: Work is hard, so pay others to do it for you?

        Personally I derive some satisfaction doing things myself. Making stuff is time consuming, and tiring at times though. There is no guarantee of success either. When things go wrong I’ve no one to blame but myself too. That might be the most difficult aspect of doing things I suppose. What I do usually works out for me, so if things go sour I’m not too hard on myself.

        Look at this picture. The two spindles laying by the switch I didn’t thread concentric to the axis. They’re scrap. The third try was a charm though.


        Sometimes you just have to persevere, and try harder. I made that whole lathe. It took me about two months. Believe me if it would have taken me 10 tries to get that spindle right I’d have done it.

        1. Not all work. What I like about RC planes (let me take give this as an example here) is that there is so much to do with them to get them flying that everyone can find something fun to do, while still being able to “buy” things particular person finds boring or too hard for some reason. The end result is as much fun (this is a hobby after all) as possible. One likes flying but hates getting fingers glued with CA? No problem, get an RTF. One wants to build and try flying different stuff (like me) and don’t have own workshop (like me) and don’t like want to spend time picking pieces of foam from a carpet (like me)? Here you go laser cutter is there. It’s all about choice.

          I’ve never been good in handiworks and I am sure (forget for a moment that I don’t have a proper place) I would not be able to assemble a lathe like yours (maybe I learn it some day). Yet I still like to do some hacking in the evening and learn about aerodynamics. That is why I choose to laser cutter.

          1. I suppose we all cannot do everything. That doesn’t stop me from trying to do as much as I can though. I could have spent my life sitting on my hands making up excuses too I guess. Many do just that.

      1. What about sandwiches? Can you cut a sandwich with your laser? How many layers of ingredients? And what about condiments? How’s it do with extra mayo? You ever cut kimchi?

        That’s where a CNC router comes in handy. And I’m not talking about a drag knife. I’m talking carbide endmill.

          1. Yup.

            I have two lasers cutters, CNC router, three lathes, a mill, tables saw, bands saw, jointer, planer, sand blaster, kiln, powdercoat gun, etc etc.

            Some purchased, some built, some upgraded.

            If people like spending days mindless cutting foam, then good for them. Same as the people who spend all their time modifying their tools, and never making anything with them.

          2. @Tony Is tables saw plural? If not then I have more table saws than you do. Back when I spent mindless days cutting foam I was commercial flat roofing, and mindlessly cutting foam was part of the job. It was one of the better aspects of it too. Use a dull knife.

          3. Yeah, table saws is plural. One big one, two small ones.

            The lasers have replaced some of their use (along with the band saw, and the scroll saw never gets used).

            Tools are cheap, it’s easier to buy another one and set it up for a dedicated job rather than futz about with set ups.

            Another example is I have four bench grinders, set up with different grade wheels, polishers and wire brushes. Got tired of swapping them.

            I do very little ‘by hand’, who has time for that?

          4. @Tony Only 4 bench grinders? That is less than half as many as I have. I got 10. I have them in different arbor sizes. Mostly 1/2″ shaft, but I have a 3/4″, and an 1-1/4″ too.

            Here’s 8 of them

            The other two are on the other side of my shop. One is a dedicated tungsten grinder for my TIG welder, the other is a diamond wheel for sharpening carbide tooling. Two weren’t finished in that picture, but they’re both done now.

          5. @Tony only 8 inches? My 3/4″ arbor grinder runs 12″ diameter wheels. Perhaps you need an eye exam? I only have an 8″ wheel on my 1 1/4″ arbor, but it likely could run a larger wheel itself. What happened to your earlier assertion that tools are cheap anyways? Are you forgetting the bullshit you’re spewing already?

    2. Why is everything cut with a powered jigsaw today? Don’t people own hand tools anymore? If someone couldn’t cut this out with a coping saw then I feel sorry for them.

      Sorry, your argument does not hold water…

      1. Your argument is facetious. People do indeed still own hand tools, and a jig saw is a powered hand tool in fact. You’d likely be better off using bow saws if you wanted to go the manual hand tool route. I’d respect that far more than some nimrod using a laser cutter on such a simple project.

        1. Tools, no matter what, are often updates or adaptions of the ones that came before. While one may prefer to use one tool in preference to another, it doesn’t diminish the worth of the person. Yet here you are calling someone a nimrod for their choice of tool. Wow.

          1. At some point devices grow beyond being tools and turn into automated machinery. While there is certainly a place for such items I’m saying a project this simplistic isn’t one of them. Performing such overkill is inelegant to say the very least. That offends my delicate sense of aesthetic sensibilities. Now quit being purposefully obtuse. It makes you a pest.

  1. Guys, all what he want to do is cut some foam, why spend U$300,00, U$800,00, U$5K,00 in a CNC or Laser machine if he can do it with U$30,00 and have fun?
    Well, looks like he’s having some fun…

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