The wire melts a slot slightly wider than its own diameter — that gap is the odpływ, and it makes outside cuts a bit smaller and holes a bit bigger than the nominal path. Hotter wire and slower feed widen the kerf; cooler and faster narrow it.
First minimise it by tuning heat and feed for a thin, clean slot. Then compensate: offset the toolpath outward by half the kerf for outside profiles and inward for holes, so the finished foam matches your dimensions. cncfoam.com lets you account for kerf in its settings. Measure your actual kerf on a test cut (cut a slot, measure its width) and use that real number rather than guessing.
First minimise it by tuning heat and feed for a thin, clean slot. Then compensate: offset the toolpath outward by half the kerf for outside profiles and inward for holes, so the finished foam matches your dimensions. cncfoam.com lets you account for kerf in its settings. Measure your actual kerf on a test cut (cut a slot, measure its width) and use that real number rather than guessing.