Foam Cutter (6 Hours to Make)




About: I love creating almost anything. I am a professional magician and guitarist/singer - so much to do so little time! Follow me on Twitter: @bricabracwizard
A video to show how this works:  I apologise in advance that I couldn't speed this video up,,,,it would have been better if it was condensed to 10 seconds anyway it's really just to show that the cutter works,

I was busily minding my own business when my partner asked me if I could make a hot wire cutter because she wanted to shape some polystyrene for some christmas decorations. I think her idea was that you stick a wire in the mains and voilá you have a hot wire cutter. So after much research here and on the net I cobbled this one together.

This is a very simple contraption.

Plywood (3 ply)
1/4" copper pipe x 6cm long
Aluminium (for the wire tensioner)
Screws and glue.
Paint - if you want to make it look good, though not essential.
Wire (nichrome....I tried the high e & b guitar strings..they don't last as long).
Electrical wire for the connections
Power Plug
Wooden batten (this is the column)
Spring (I used an old camping bed spring)
Coat Hanger (very technical now)
Transformer (preferably the one you use for 50W halogen lights - 12volt output)
Dimmer (you can control the temperature of the wire)
Power Switch
Fuse Holder and Fuse (I used an 3 amp fuse)
4 Rubber feet

This can be made using only hand tools....but I used:
Power drill
Circular Saw
Wire Cutter
Soldering Iron and Solder

Step 1: Making the Box

My box was already made it was being thrown out by a neighbour.  Cut the wood to size and screw and glue your box...leave the bottom off to install the electronics. Make sure to cut out the square to insert your column and drill out the hole to fit a copper pipe.

Step 2: Wiring It Up

Connect the power through the fuse, then active wire to the switch, output from the dimmer goes to the transformer high voltage side.  The ground/neutral wire goes straight to the transformer.  The 12volt output from the transformer connects to each end of the nichrome wire.  Turn the dimmer all the way anti-clockwise and turn on and gradually increase the current until you are cutting through the polystyrene/foam.  It really is that simple....don't touch the wire and if you are not confident to wire this up get someone who first!

Step 3: Final Steps

Now link everything together.  Cut a hole in the front of the box for your dimmer/switch.  Make holes in the back for your power cable and fuse holder.  Put a knot in the power cable so that it can't be accidentally pulled out.  Tie the nichrome wire around the screw in the base and pull the tensioner down to screw the wire to your connector on the arm.  Finally put 4 rubber feet on the base.



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    12 Discussions


    3 years ago

    nice bro..

    can i buy 110volts input and 12volts 2 amps transformer for this?

    i want to cut 1inch and below gauge thermocol sheet what gauge of nichrome wire i wants to use??

    could you pls tell me bro>..

    my id:

    watsapp: 9490962430 plss bro its a urgent project.

    1 reply

    Reply 3 years ago

    This instructable goes into more depth about what wires and voltage to use...check it out:


    4 years ago on Introduction

    I tried to make it but not much luck I think it is because I used electronic transformer for halogen lights. Any ideas? I am sure I connected all right.

    When I make it work I'll post picture. I used for base drill stand.

    3 replies

    I used an halogen transformer rated for 50watts and it worked. Make sure your wire is not too thick. You could also wire two transformers in parallel to get more current. Good luck!

    I changed electronic halogen lighting transformer for regular one and it works. Thank you for nice tutorial. I used drill stand as base that holds hot wire.

    Great! You should click the 'I Made It' button and put in a picture of your foam cutter. Thanks for your nice comments.


    5 years ago on Introduction

    Can you please explain the set up for the connection on the base with the copper and screw?


    5 years ago on Introduction

    Very nostalgic for me. I built almost the exact same cutter back 1976. We used it to shape Styrofoam for architectural and technical drawing classes.

    1 reply