DIY Hot Wire Cutter for Plexiglass, Cardboard and Foam





Introduction: DIY Hot Wire Cutter for Plexiglass, Cardboard and Foam

About: My name is Simon Sörensen and I am the creator of RCLifeOn. I´m 19 years old and live in a town called Trollhättan, located in the southwestern part of Sweden. I´ve been in the RC hobby...

This Instructable will demonstrate how you can build your own hot wire cutter, able to slice through foam, cardboard and even plexiglass!

Step 1: How Does a Hot Wire Cutter Work?

A hot wire cutter works by a wire, often nichrome or in my case kanthal wire, which is heated via electrical resistance. As the wire reach high temperatures it slices through materials by melting it just in advance of contact.

Step 2: The Frame

Let me start by saying that the stated measurements are not crucial for a functional wire cutter. Use the materials you can find at home, and benefit from my Instructable as a guidance for assembly and inspiration.

To make it super simple I used long screws for standoffs, this will lift the frame up and give clearance for what we will put underneath the frame. Also, glue pieces of foam to the screw heads, this will remove the risk of scratching your furnitures.

Step 3: The Wire Holder

In order for the wire to make the 90° turns you will have to make two brackets. Their main purpose is to softly guide the wire 90°, but also makes it easier to attach the alligator clips as you can slide them up and down to adjust the temperature. More about this later.

The brackets consists of two 15x15 wooden booms, and a 25mm dowel in between. Once these are glued you can use a dremel to make a groove, this will ensure the wire stays in place.

The smaller bracket on the bottom can be glued in place and does not require screws. However, the top bracket has a 30° angle, and therefore a higher risk of breaking. Unless you're using wood glue, it's probably a good idea to secure in place with screws in each wooden boom.

Take two screws and put one some distance away from the top bracket, preferably with an 45° angle. Do the same on the bottom, though the angle is not necessary. These screws will be holding the wire, see next step.

Step 4: Attach the Wire

Begin with cutting a long piece of your wire, could be kanthal or nichrome. Make a loop and tighten it around one end of the spring. Take a second shorter piece of wire and tight it around the other end of the spring. Attach the shorter piece of wire to the top screw by a knot or many revolutions. Drill a hole in line with the direction of the wire, and tension the wire as you attach the longer end of the wire to the screw on the bottom of the frame. The wire should feel like a guitar string.

TIP: If you can't find a spring, try manufacture one at home. You can find a lot of information by searching for "How to make a small spring".

Step 5: The Wiring

Alligator clips are great because they make you able to adjust the temperature very easily. Just like a dimmer. More about this in the final step. Cut two pieces of at least 18AWG, one long and one short. Solder on the alligator clips and attach them underneath the top and bottom brackets (see pictures). I decided to use a power distribution board, as this makes it easier to solder additional wires, LED's or whatever that runs on 12V. However, you could definitely solder the alligator clips straight to the connector.

Step 6: Power

There's many ways you could power the hot wire cutter; battery, power supply, USB and even solar cells! However, a lot of people don't have access to a 12V power supply, and that's why I decided to power my hot wire cutter with a 2200mAh 3S lithium polymer battery. You can buy these batteries from Hobbyking for only 10$. One battery only lasts for 20min of active cutting, so I will probably purchase a higher capacity battery to achieve longer cutting time.

I also added some LED's to visually see when the wire cutter is powered.

Step 7: What Can You Cut?

Foam, cardboard and plexiglass got sliced like butter! I believe this is what makes this one special, as most hot wire cutters only have the power to cut foam.

You can easily adjust the temperature by sliding the top alligator clip up and down. However, remember that higher temperature increases the risk of the wire breaking. Though, this is not a big problem because changing the kanthal wire only takes a minute.

I also made some 3D letters (RC - radio control). Let me know, what have you done with a hot wire cutter? Comment below!



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Aside from the problems of using a battery. How do you keep the parts that are melted from re-bonding after passing the hot wire?

1 reply

The foam never really touches the wire, the foam heats up and shrinks away from the wire. If you are burning foam you are moving too fast. I cut foam for metal casting and the pieces never have fused back together. I use a 30 volt dc 5 amp power supply to heat my wire, bought it off Amazon, It would not take very many 10$ batteries to pay for it and it is completely adjustable for wire size and length of wire.

This is a deceptively simple project that provides a cheap, useful addition to a hobbyist maker's small basement shop. Well-written and explained. Got any suggestions/ideas for adapting the cutter to take outlet power?

1 reply

There's a similar project here which uses no batteries:

I want to thank you for this instructable, I have used nichrome wire from hair dryer and an old 96Watts 12Vac garden lights power supply.


If you already have suitable wire, disregard. If shopping, Amazon has the kanthal wire in spools starting around $4 depending on the gauge you want.

Thanks for this, really looking forward to giving it a try. looking at other power source, as looks like a few others, just 'cuz I'd like to think it would be more permanent. Replacing a battery is a pain no matter what type. Any attempts at something more permanent, or a thumbs up to try one of the other comments approach? Looking to save some of my collectables from weather and moisture, so display cases is where I'm heading w/ this. Thanks again, Aloha

I do a lot of electronics projects that I build custom enclosures for out of acrylic and plexiglass. I like to see (and show off) what is inside the box rather than using a black "project box". This would be so much easier than hand cutting. Thanks for the awesome post. This is my next project, to be sure.

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Display boxes was my first thought as well when I first seen this. I was wondering if you've had a go at this yet? I live in Hawaii, and finding "on hand" items can prove difficult and very expensive. Even salvaging is a chore as most hobbyists already have claim, or auntie and uncle think that 90's vcr is still state-of-the-art, and definitely worth 60 bucks. Looking for info in other comments, but since your along the same desired use any info would be much appreciated. Thanks and Aloha

Definately not a good idea to short circuit a lipo - I would replace the lipo with a power supply unit or variable charger - a lipo that is shorted like this will expand and explode....and I have a mate who burnt his dad's loft down with a 2 cell - imagine what a bigger lipo could do to your face?!

Looking at the schematic it seems as though you are literally creating a short-circuit with a li-po battery. From my RC days I know that it is extremely dangerous to short-out a li-po or any other battery for that matter, in fear for explosion. Because yours has not exploded, and is instead creating energy in the form of heat, what kind of wire are you using?

Great Instructable

Great Workshop

power only by battery,(do not connect to mains) Suitable wire for cutting use fishing tackle wire (NICROME), for resistance use old style wire kettle heating element ,adjust heavy style bulldog clips slowly along element wire until cutting wire glows a light red, You are Ready to cut foam.

Nice little cutter; I made a long-reach one years ago to cut polystyrene sheets for our house cladding/insulation.

One word of warning: Be careful not to breath in the fumes from cutting, they're poisonous. Maybe put a desktop fan next to the cutter and/or always use it outdoors.

Could I use this to cut shapes in old vinyl records? If you have any around, try it and let me know how it works. PS, and or pvc pipe. thanks.

Never seen a battery-powered wire cutter. Very cool. Where would one find the wire for a project like this?

2 replies

Stainless steel safety wire works quite nicely. Used it to cut polypropylene wing cores for combat foamies for a couple of years.

Ebay, Amazon or even your local hardware shop could have the wire. Thanks for reading my Instructable!

Nice, thanks for the instructable.

Out of interest an old Desktop PC power supply (ATX or other) can be had for near nothing or about £10 brand new in the UK these can provide a fair bit of current.

If you get hold of a cheap ammeter (moving coil type will do) and put it in series with your supply. Whenever you find the right spot for the croc clip to cut whatever then mark it on the ammeter so you can get repeatability and fast set ups..

I need an instructable on how I can get my workshop to look as organised and clean as yours :-)