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Cutting foam with a hot wire is a common technique to shape foam in a wide variety of shapes. If you want to cut something detailed and precise, like an airfoil, you probably want to use a computer-controlled cutting tool. Here [Michael Rechtin] has been working on creating a very versatile DIY CNC hot wire cutter, with the results recently announced in a video, along with the GitHub project repository if you want to give it a shake yourself.
Key in hot wire foam cutting is getting the nickel-chromium wire hot enough to gently slice through the foam rather than annihilating it or having the wire encounter significant resistance. For an automated cutter it either needs to be able to adjust the current on the fly, or have a predetermined optimal current for the cutting speed.
The machine itself is a 4-axis system, allowing the wire to be moved just about any way in between the two sides. It uses typical NEMA 17 stepper motors, along with other components that you’d find on a 3D printer. The same is true for the control board that processes the g-code from the software.
The unique part is the pulley-based mechanism that tensions the cutting wire, along with the way that the current gets passed through the wire, which uses MIG welding tips rather than just some alligator clips, which would probably also have worked but not looked as nice.
There are a few 3D-printed parts for which the STLs are provided, and the design is such that the entire assembly can be fairly easily collapsed into a compact shape that’s much easier to store if you’re not cutting foam every single day. For [Michael] cutting airfoils is the main use, for which you got a few software packages that are mentioned in the video.
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