The wire melts a slot slightly wider than its own diameter — that gap is the зазор, 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. https://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. https://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.