DIY Hot Wire Cutter - Portable Version




Introduction: DIY Hot Wire Cutter - Portable Version

My name is Simon Sörensen and I am the creator of RCLifeOn. I´m 19 years old and live ...

In this Instructable I will build a handheld DIY hot wire cutter. Powerful enough to cut through foam, cardboard, plexiglass, acrylic and PVC!

Step 1: How Does It Work?

A hot wire cutter works by applying current to a metal wire. Due to the wire having electrical resistance, which means that they resist the motion of electrons, the electrons bump into atoms on the outside of the wire, and some of their kinetic energy is given to the atoms as thermal energy. This thermal energy causes the wire to heat up.

As the wire is passed through the material to be cut, the heat from the wire vaporises the material just in advance of contact.

Step 2: Electronics

This hot wire cutter is super simple to make, and is made by using very inexpensive parts and electrical components. A battery is necessary to power the controller and heat up the wire. It's a small 2S (7.4V) lithium polymer battery for only 6$! In order to control the amount of current going through the nichrome wire we can use a small servo tester. Sounds expensive? Ha, the servo tester is only a dollar! You also need a brushed electric speed controller, also called ESC. This device steps down the power from the battery to the controller, as the controller only handles 5V. The ESC is very cheap and can be used for many projects in the future.

Servo tester:
10A brushed ESC: (7.4V) battery:

The wire can be made from nichrome, kanthal or stainless steel. I recommend kanthal, but nichrome is more common. You can find it here:

  • You also need a JST connector (female)
  • Shrink tubing
  • Alligator clips
  • 400mm 16AWG wire
  • Screws
  • A spring and a wing nut
Everything can be found at your local hardware store and Ebay!

Step 3: The Frame

Gather some 15x15mm square wood, and some wooden dowels with a diameter of 15mm. Cut 2 pieces of the wooden dowels 150mm long. You also need two pieces of square wood, 310mm and 320mm.

Assemble it according to picture number two using screws of appropriate length and size. Drill a hole in the very end of the shorter (310mm) piece, the hole must be larger than the screw you intend to use.

Insert the bolt through the hole and use a washer and nut in order to lock the nichrome wire into place. Thread the wing nut a couple of threads, not more than a few threads!

Use a small screw to lock the spring in place. Then take a piece of wire and lock it into place. The wing nut can now be threaded all the way to adjust the tension on the wire. If the wire keeps snapping (break) you must release some tension!

Step 4: Electronic Assembly

Solder the 16AWG wires to the alligator clips and cover it with heat shrink tubing. This is not really necessary but makes it look more clean. Attach the clips to the wire according to picture number two. The clips can be moved closer or futher apart to increase or decrease the resistance. The futher apart the clips are the more power you need to heat it up, but the larger (thicker) foam you can cut. By moving the clips closer to each other you will decrease the power required to heat it up, but the cutting thickness decreases.

Connect the 10A ESC to the controller and tape them together using electrical tape. Solder the JST connector to the negative and positive wire from the alligator clips. Attach the battery to the frame and connect the power.

The dial can be used to increase or decrease the current flow from the battery. This is very useful and convenient! Let's cut something!

Step 5: What Can We Cut?

You will be surprised how powerful the cutter can be! I began with some 6mm foam, and because of the soft material you can increase the temperature and therefore gain cutting speed. For the 50mm thick foam you need to decrease current (decrease temperature) and go slower because more foam has to be cut. However, you can still cut it quite quickly!

Now, here's when it start to become interesting. Even though it cuts slow, I was able to cut through PVC, cardboard, plexiglass and acrylic. Because of the portable design and awesome performance I use this useful tool all the time! This is a "must have" tool when building! Did you build it? Share it in the comments!

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23 Discussions



Wow! So powerful! Was getting tired of feeble foamcutters b/c I cut building foam. Will have to try building one.


2 replies

Hi was wondering if you built your cutter yet. I too am thinking about this project for building foam also. Is the the foam your working with sprayed on with a 2 part mix and if you did try what kind of fumes did it give off

I did build a number of them. It was a mixed result; still not powerful enough for building foam so I started to just bypass all the electronics and split an adaptor cord directly. I don't know about 2-part mix but it might work; I usually just cut 2-part foam with a razor/x-acto knife.

There is a switch showing on the servo controller. How is it connected? It's not shown on the components list.

Instead of the servo tester, can I use a potentiometer?

I built a larger table top version of this cutter not long ago. I added guides to it to allow very straight precision cuts. I use it primarily for making acrylic cases for my projects. This is my next project. The portability is a great concept and I imagine I could come up with some kind of guides for better precision.

One question. How much time do you get from the battery you used here? I have been using a 7AH SLA with awesome time results and was wondering how this one might fare in use.

Awesome 'ible in any case.

I saw a similar one, but much larger here on "Instructables", but it was large and bulky. So this is a FANTASTIC addition to any craftroom or workshop. I do a lot of crafting and cut various different kinds of items, so this would be so helpful to me. I can't wait to build it and I'm going to build two so that if one breaks or just wears out I'll have one already to go. Thank you for your creation!

Very creative thinking - I didn't know there were all sorts of RC gadgets like these.

I do have a concern that the servo tester might not have enough current capability and you are overloading it

A quick calculation showing the resistance of the kanthal wire, the current and expected temperature of the wire would really add to this instructable. I'm an engineer, so it's always "show me the numbers" :)

Good luck


1 reply

The servo tester only supplies the control PWM signal for the ESC (normally supplied by RC receivers), so no worry about overloading here. :)

You could do something similar with PVC pipe and put the bulk of the wires, etc inside the pipe.

It is a very useful item.

Can you please specify the gauge size of nichrome or kanthal wire used?

Really cool project! Just a word of warning though. If you burn PVC, it can let off hydrochloric acid fumes which can be very dangerous, especially if inhaled or if it gets in your eyes. Cutting the foam and acrylic should be fine though.

That's a nice tool....I'm putting together a shopping list!
I do suggest putting a velcro or elastic strap over both the grip and wrist brace portions. Watching the demos, I realized that it would be really easy to fumble it and end up with the hot wire kicking back onto your arm or fall on a leg or foot. While the wire does cool quickly, it's still a possibility and an easy precaution to take.

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