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!