I'm currently working on finding a way to cut reticulated foam to improve waveguides.
Here you can see an old Birko 120w soldring iron. I flattened the tip, then drilled a small hole to fit the copper wire.
The wire is shaped to the profile of the waveguide.
Unfortunately only the first 12mm or so of the wire was hot enough to cut the foam. It isn't likely that it will get hot enough and stay hot enough for the entire wire to do the job. I will need to either use just the tip, or investigate other methods. I will be trying a regular hot knife.