Portable Hot Wire Foam Cutter





Introduction: Portable Hot Wire Foam Cutter

About: I'm Frederick and I build electronic things, mostly with Raspberry Pi. Using my 3D printer, CNC machine or hand tools, I make custom frames and enclosures for my projects. These projects are a way for me to ...

I was thinking of using foam in a future project, so I played with the idea to make my own foam cutter to help me with that future build. It turns out a foam cutter is rather easy to make!

The build uses two AA batteries to heat up a piece of 32SWG nichrome wire, capable of cutting through dense foam like XPS.

Warning: make sure you use this in a well ventilated room, as some potentially harmful fumes can be released when cutting, depending on the foam you are using.

Step 1: Handle

I wanted to make a robust handle for the foam cutter and had a try using wood.

First, I put tape on a piece of wood and drew the shape of half the handle. Using double sided tape, a second piece was stacked, so that when cutting using the jigsaw, both pieces would have the same shape.

With both halves cut out, I glued them together by the handle, and used some clamps to hold it in place while the glue dried.

Once dried, a router was used to round over the edges, making it more comfortable to hold while looking a bit more finished. Finally, holes were drilled at the extremities, to be able to pass some screws to attach the nichrome wire to.

Step 2: Wiring

The wiring is simple: a battery pack is wired to the extremities of the handle, with a nichrome wire connecting both ends.

To make things slightly easier to wire, I used crimping lugs at the ends of the wires and nichrome wire.

The battery holder is one for two AA batteries, which in my case seems to provide enough power. You can experiment with larger holders, for three or more batteries, or perhaps even try using a 9V battery. Just make sure the nichrome wire doesn't get red hot. The holder is attached to the handle using hot glue.

I didn't add a switch to keep things simple, and because it's very easy to pop out one of the batteries when finished. You could add a switch or even use a battery holder with integrated switch if you prefer.

Step 3: Video

That's it really! Using two AA batteries, I was able to cut XPS foam (quite dense) at a rate of 5mm/s for a thickness of 3cm. Check out the video for the entire build process and some cutting demonstrations.



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    19 Discussions

    Simple......Yet Brilliant !!

    I think this is a great looking foam cutter. The only thing I would consider adding, stealing from Grant Thompson's design, is a spring attatched to one end of the fork to keep the wire tight. It looks like you use the wire well for it not being tight, but not being as good an artisan as you seem to be, I would want my wire tighter.

    Very clever and I'll try to make one myself. Thank you

    keep in mind also that some foams are flammable. get that wire red hot and you'll have a big problem.

    I bury my head in this site and don't come up hours, normally from the Mrs saying 'will you empty that bin' or 'when are you going to do the dishes'? It's projects like this that are so lo tech but brilliant in saving money that amaze me.

    Outstanding Frederick! (but the Mrs says for gods sake stop making stuff like this so he can do the hoovering!!)

    2 replies

    Haha, thanks Paul! I know the feeling! Though I was able to find my wife a hobby she really enjoys, so now we're both making things :D

    Frederick, I'd never try and find her a hobby, I'd be constantly worrying as to where she would stick her crochet hook!


    1 year ago

    Wonderfully simple but a very useful tool for craftsmen.

    Nice instructable.

    1 reply

    where do you get this i can only find "Nichrome 80 - 100 ft 32 Gauge AWG Resistance Wire 0.20mm 32g 100'" on amazon

    1 reply

    Looks easy enough to make, even I could do that :D. Certain (tropical) hardwoods can cause (severe) allergic reactions. Just saying cuz I saw all that sawdust around your work bench. Looks like you where using Meranti so that one is not too bad but I'ld wear a FFP3 mask. http://www.wood-database.com/wood-articles/wood-allergies-and-toxicity/

    1 reply

    Thanks for the heads up fons. I'm one of those people with no allergies, so I tend to not think about this aspect.

    It is indeed Meranti, and caused a real mess. My shed is well ventilated, but I'll certainly look into purchasing a mask for future project!

    Thanks for your instructable! Would this work to cut the big styrofoam blocks that are used to hold up docks on the water?

    1 reply

    I'm not sure. It's ideal for small pieces of foam, but may not bee powerful enough for larger. Perhaps by using more power than just 2AA batteries.


    1 year ago

    Be careful cutting foam without proper ventilation. Foam in the urethane/esters can outgas cyanid. The foam in your post are in this family. Otherwise, nice idea.

    1 reply