Rigid urethane foams are no problem to mill - spindle speeds vary according to the size of the tool, but at least with the lighter types it doesn't really matter too much. The main problem with them is the horrible clinging dust particles that stick to everything. This is less of an issue with the higher-density urethane foams meant for milling, like Renshape, which make shavings rather than powder.
But EVA foam is a different matter. It's flexible (at least the kind I know about is) and I doubt it would be easy -or even possible - to cut it cleanly. But maybe someone here has had some success with it - one never knows...
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