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I am designing an automated hot wire foam cutter for my project, and I am stuck on the computation for the most viable cutting speed of my design. The cutting tool used is a nichrome wire and the medium is a polystyrene board. How do I solve for the best cutting speed of a heated nichrome wire given the melting point of styrofoam boards have a melting point of 240 degrees Celsius, and the Styro board has a thickness of about half an inch.

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  • $\begingroup$ Can't you just experiment? $\endgroup$ – HandyHowie May 29 '19 at 10:18
  • $\begingroup$ Are all styro boards created equal? if not then you need some adjustment of x +/- y% to cope... $\endgroup$ – Solar Mike May 29 '19 at 11:13
  • $\begingroup$ Are you just using a 12 volt battery or similar to supply the power for the cutting wire? if so, you could always add in a high wattage potentiometer (pot) for easy adjustment. You could start with the pot at 0 resistance and then measure the temperature if it's too hot, just add a bit more resistance. If it's not hot enough, then you'd need more power. This would also allow you to adjust the temperature while cutting if needed. either way, @HandyHowie sounds right about just experimenting a bit. $\endgroup$ – gerrgheiser May 29 '19 at 13:36
  • $\begingroup$ I doubt if anyone calculates such things. However, you need to melt a certain length of cut, the depth of melting can be seen by observation and you MAY be able to source the latent heat of fusion of the material), The speed of cut is limited by the energy required to melt the above calculated amount of plastic and power input. Margin of error is liable to be vast. Experiment probably serves you better. $\endgroup$ – Russell McMahon May 29 '19 at 13:47
  • $\begingroup$ There is already a wide variety of CNC hotwire styrofoam cutting machines. some can create sophisticated 3d objects, such as balustrades, 3d lettering for building monuments, sculptures. With a price range of $150to 1000. search for them, some even rent the machine. $\endgroup$ – kamran May 29 '19 at 18:55
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Here is what I know, from my slight experience hand-cutting foam for model airplanes, and from things I've heard from actual experts:

  1. It varies with wire temperature, which, in turn, varies with applied voltage and cutting speed. So there's no one right speed, and things may change dramatically if you actively control for wire temperature.
  2. It varies with foam density (although usually the model airplane guys are using the lightest foam they can lay their hands on).
  3. You want to look for a range, because if you're cutting something tapered then the big end needs to go faster than the little end.
  4. To some small extent you can compensate for slow cutting by allowing for a bigger kerf -- a hot wire going slowly through foam melts more material, and you can sorta-kinda fix that.

I think you'll just need to experiment.

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