Make your own hot-wire or styrofoam cutter

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Last modified on: February 20th 2024


Filicutter is a tool to hot cut styrofoam, which allows you to highlight any piece recovered, and do so a lot of things: modeling, layout, visual arts, etc ...

Filicutter principle 1

The principle is quite simple, there is a strong electric current in a thin resistive wire. The wire under the effect of current, heat and cut easily and cleanly styrofoam, much much better than with a knife or a cutter, particularly for large pieces (> 5 cm thick). It can also be use to cut plastic or synthetic foam.

Build a filicutter is only adding a current source to resistive electrical wire, adding a control switch and possibly a light bulb to limit a bit the current passing through the wires.

Filicutter principle 2

And of course mount the whole on a structure, insulated, easy to handle, so you can control the hot wire during phases of cut. The idea was to do something that looks like a bit to a saw wire, a kind of huge "U" who owns a handful at the end. Like this:

Filicutter principle 3

This way you control switching on/off heater wire with a finger, and guide cutting with the same hand.

What you need

How to

When you've read the principle, you can do it in your way. Here is mine, made with resistive wire and car battery charger.

Fold metalic pipe to make the "U" according to your dimensions.
Cut the handle in plastic pipe. On top of this pipe, make (using a saw) a place for the "U". Make a hole for your push-button, in the right place for your finger as a trigger. Connect two wires to push-button, and put them inside the handle. filicutter
Put the "U" in the handle, let 2 cm - 1 inch exceed, and fix it by making two holes througt the handle. Put two bolts in those holes, and put two nuts on the other side. You should have in your hand something light, with push-boutton right under your index. filicutter
Add then the resistive wire on the "U". On top, use a small metallic bolt with a ring head. You shoud use metallic bolt because and electric contact is needed on that side. filicutter
On bottom, contrarily wire should be insulate from the "U": use a small piece of wood, fixed with another bolt and nut, then another metallic bolt with a ring head. filicutter
Then connect:
  1. One arrival of power to the "U" (using an alligator clip for example).
  2. The other power arrival on one probe of the push-buttonl
  3. The second probe of push-button to the bottom metallic bolt with a ring head

That's it, it's over, you can now discover the happiness of precision cutting styrofoam...

Alain told me that you should be careful with styrofoam smokes when cutting, they are toxic and should not be breath.


Filicutter with handle like this one is very useful for... sculpturing styrofoam, but it's a bit difficult to make straight cuts.

If you have this kind of cuts to do, it could be interesting to improve it by making a kind of stand. The idea is to make this stand with a right-angle system and another push-button commanded by your feet, so that your two hands are free to control the styrofoam piece move.

To do that, you should make a small table, with a hole in and where the wire pass through. Table and filicutter should be in right angle, stable and connected, for example in a clamp.


Home made filicutter

Here is some photos of mine (click to enlarge) :

filicutter filicutter filicutter filicutter

Grip detailTop nail detailFixing detail
filicutter filicutter filicutter filicutter
Connected to a car abatterry chargerWorking on claw-back styrofoam pieceSharpen curtCutting table...
filicutter filicutter filicutter filicutter a clamp.Filicutter in p.laceFeet action
filicutter filicutter filicutter filicutter
Also cut shapes...
filicutter filicutter
more complex.Also cut foam


You could now, according to your needs, enhance the filicutter. Just in case, here is some lines of enquiry:

Of course, if you want to give or ask precisions or informations, don't hesitate to contact me.

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The 43 comments already posted on this page
  • I have 4 x 8 sheets 6 in thick
    I use 12 v car battery and for wire i use continuous welding wire heavy gauge for fabrication
    You will have to tighten wire when it heatsup
    It cuts all my sheets of insulation 1 in 2 in 3 ect...
    You will need to practice but it works
    Posted by MIKE june 16th 2019 at 20:19 n° 43
  • Yes, I think so. I got friends who cut foam mattress for their baby bed with it.
    Posted by jh june 20th 2018 at 09:30 n° 42
  • Great tutorial, I've been entertaining making one of these or something similar to try and cut a memory foam pillow. With it being so dense do you think this method would work?
    Posted by Levi june 20th 2018 at 08:57 n° 41
  • Yes it is, and everything about the cutting wire is in the text page.
    For the battery wire use standard cooper wire of appropriate diameter (not too small).
    Posted by jh may 1st 2018 at 21:11 n° 40
  • I like the page. I am desperately trying to make a hotwire cutter but getting kind of confused. Ive spent about a hundred dollars and gotten nowhere with what I thought was good information that I dug up on the internet. I like the idea of using a car battery. I need to be able to cut styrofoam about 4 feet in length.Is it possible with this kind of setup? What kind of wire will I need to hook up battery and what kind of wire for the cutting? Id appreciate your comment. Thank you.
    Posted by Jetjanitor may 1st 2018 at 20:59 n° 39
  • Dont go to Jacobs online. Service is terrible
    Posted by Jet april 22th 2018 at 23:36 n° 38
  • I don't know, but it's a rather slow temperature, I mean the wire don't need to become red.
    Posted by jh january 6th 2018 at 06:22 n° 37
  • What is optimal temperature for cutting styrofoam and how to make ( for instance) 100W cutter if I have transformer of 17,5V?
    Posted by jure january 5th 2018 at 15:11 n° 36
  • Science concept?
    Posted by jd november 30th 2017 at 15:13 n° 35
  • It depend of the size (diameter) of your wire, could be tried.
    Posted by jh september 29th 2016 at 08:56 n° 34
  • Can I use guitar string on 9 volt power supply, I am combining my 5 4 volts phone charger
    Posted by simon september 27th 2016 at 17:39 n° 33
  • It depend on your wire size, but should be.
    Posted by jh july 24th 2016 at 03:02 n° 32
  • Would 18 volts be adequate?
    Posted by Ben july 23th 2016 at 01:16 n° 31
  • You bet. goto:
    Posted by limpinlou march 30th 2016 at 18:54 n° 30
  • No idea what it is, anybody else?
    Posted by jh february 12th 2016 at 08:49 n° 29
  • I have a microme 80 wire of 26 gauge .is it useful for make a hot wire fome cutter
    Posted by Anonymous february 4th 2016 at 16:49 n° 28
  • Increase
    Posted by jh december 19th 2015 at 14:48 n° 27
  • 6 volts
    Posted by Sam december 19th 2015 at 10:34 n° 26
  • I'm afraid it's a bit low.
    Posted by jh december 19th 2015 at 10:28 n° 25
  • 4volts battry can work?
    It's just for science project.
    Posted by Sam december 19th 2015 at 10:22 n° 24
  • You can use the tungsten wire out of an electric bar fire with a 6v (square) battery for a more portable unit.
    Posted by ian september 21th 2015 at 16:37 n° 23
  • No, I don't think so.
    But you'll certainly need to push the piece of foam a bit slower, to get a nice cut.
    Posted by jh february 27th 2014 at 08:50 n° 22
  • We are trying to construct a hot wire cutter to split 4 inch thick foam board into 2 inch thick. It needs to have an approximate 4 ft. cutting wire area. Will we need to increase voltage or will a commercial battery charger work for this length cutting wire?
    Posted by TED february 26th 2014 at 19:52 n° 21
  • Already indicated, but it's 0.4 mm.
    Anyway no need to be precise, any wire will be ok.
    Posted by jh february 25th 2014 at 11:46 n° 20
  • It sounds too good for me and be the fact that I have much interest in the subject matter. I still get lost with the way you are gaging the wires. Could u please use the (mm) just for me to understand
    Posted by CHRIS february 25th 2014 at 10:25 n° 19
  • It's a 4/10 of mm thick
    Posted by jh february 19th 2014 at 13:31 n° 18
  • Thank you for this great tutorial. What is the thickness of the resistive wire that you used? Thanks.
    Posted by Jim february 19th 2014 at 01:22 n° 17
  • Yes, no problem.
    Posted by jh march 21th 2013 at 09:11 n° 16
  • Can i use adapters so that i can reduce the volts if i'll plug it in a house electric outlet?
    Posted by JC march 21th 2013 at 07:51 n° 15
  • Not so much...
    Posted by jh march 8th 2013 at 11:07 n° 14
  • I just wana run to get one it seems to complex
    Posted by Anonymous march 8th 2013 at 04:57 n° 13
  • Yes, make tests to find the right one.
    Posted by jh march 6th 2013 at 09:04 n° 12
  • Cain i used 24dc 1.5amp rectifier,what size of wire element should i used
    Posted by Anonymous march 5th 2013 at 03:31 n° 11
  • Yes, but you need a cutting wire of at least 20 cm long.
    Posted by jh january 21th 2013 at 13:23 n° 10
  • I have sheets of strofoam which is 30" X 20", and is 6 cms wide. What I need to do is to slice the sheet into 1 cm widths. Will I be able to do this, using your method?
    Posted by Joyce january 21th 2013 at 06:49 n° 9
  • No, too high in volts and so too dangerous.
    Posted by jh june 28th 2012 at 15:03 n° 8
  • How about household current? (e.g. plug into house outlet?)
    Posted by Bob june 28th 2012 at 14:26 n° 7
  • It's a car battery, 12 volts.
    Posted by jh april 21th 2012 at 10:06 n° 6
  • Good job on your wen page! Is the battery 6 Volt or 9 Volt?
    Posted by Maynard april 20th 2012 at 21:34 n° 5
  • I don't know, probably yes, but it should be tried.
    Posted by jh november 21th 2011 at 11:51 n° 4
  • Will guitar string work?? Have tons of that.
    Posted by papastash november 21th 2011 at 08:08 n° 3
  • Maybe you can use the heating wires inside a reformed old hair-dryer?
    Posted by jh october 2nd 2010 at 16:50 n° 2
  • I want to make a hot wire cutter to cut round grooves [1/2"; 3/4"; 1"; the styrofoam portion of ICF [insulated concrete blocks] after installation for plumbing and electrical channels. How can I make a cutting edge in a U shape for this purpose? 26 gage nichrom wire is too flexable for the U.
    Posted by David october 1st 2010 at 21:48 n° 1
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