The FI-FoamBurner is a lightweight easy to use hot wire foam cutter. Built from easy to get and assemble parts, its can be made in a afternoon and used for a lifetime. Parts are easy to replace and the power supply system can variate the temperature to cut the desired type of foam.
During my initial testing of my FI-AUAV project I needed a lightweight airframe that I could fly to test autopilot code. Knowing that 70%+ flights would end in a crash due to runtime code issues, I needed a method to reproduce airframes easily and with little cost. I decided to use high density foam for the airframe which allow for easy customization for experimentation.
Foam had a couple of drawbacks, one being it's not easy to cut thick slices of dense foam with a knife or saw, and when you do use those methods, it’s very messy. Professionals use hot wires to cut foam fast and precise, so I figured the easiest way to cut foam at home was to emulate the professionals.
The first step was getting a spool of nichrome wire. Nichrome wire is a electrically resistive material made up of nickel and chrome used in heating elements & hair dryers. At first I was unsure how much electricity to apply to the wire to achieve the proper temperature to cut foam. So I decided to get my temperature sensor from my reflow solder plate project (See FI-ATCSRP Project page), I attached the glass braided wire to the nichrome wire and attached the nichrome wire to a variable DC power supply.
After a hour or so of testing with the variable DC power supply, I decided to switch to a AC power supply. Curious to see the raw power of 120VAC 60Hz wall plug power, I connected a 12 inch piece of wire only to watch the wire almost evaporate in less then a second. After some math and some final tests, I decided to use a variable AC door bell transformer. The transformer I found would output 120VAC 60Hz electricity to either 8VAC, 16VAC or 24VAC.
One interesting fact I found with the nichrome wire was that the heat generated by the wire is only done between the points of VCC and GND. Thus you can use a larger piece of wire then needed and not worry about insulating the heat from the frame that holds the wire. With that new found fact in mind I started working on the frame to hold the wire.
In the beginning I had a couple goals in mind for this project. The most important to me was that the tool in its final state would need to be durable and simple. Durable so that I could use it for a long time and simple so that when there was an issue, it could be fixed fast and cheap.
Feel free to contact me anytime by any of the mediums listed on the about page or via the contact form below.
Email: fisher.matt at gmail.com