I have never had much success cutting either open-cell or closed-cell Styrofoam or any other kind of "foamed" plastic, probably because I lacked the patience to find the right temperature for the nichrome cutting wire. My fallback position was to use a really sharp knife, which is clumsy and time-consuming even with straight-line cuts. Fugettaboutit for round or anything resembling wavy cuts.
I think a lot of hobby-type experimentation is of the trial-and-error persuasion. I know that's how I approached it while growing up and trying to figure out what electricity and (later) electronics was all about. Luckily, I didn't electrocute myself or burn the house down, although I have been electrically shocked many times and have on several occasions accidentally started small electrical fires.
The key to learning by trial-and-error is to keep careful records, completely describing (as much as possible) what you are trying to do, how you are trying to do it, and the outcome from your efforts.
@Bluejets indirectly referred to this methodology with his comment, "Marked each setting as the need arose for future reference."
"Trial-and-error" also requires at least
some understanding of what you are trying to do. This understanding will assist in allowing you to set parameters for the experiment. For example, in
@Bluejets nichrome wire cutting experiments on Styrofoam there were limits he self-imposed on the voltage, current, and nichrome wire diameter and length. He probably acquired knowledge of these limits from earlier attempts to control the electrical heating of nichrome wire and applied them to cutting Styrofoam. Clearly (perhaps) a red-hot wire would melt too much "stuff" while a luke-warm to the touch wire wouldn't melt anything at all. The devil is in the details of finding out exactly how much voltage and how much current is needed to make a clean cut. I would imagine that how fast you moved the cutting wire through the Styrofoam would be a factor to consider, but perhaps not easy to control.
