Sticky residue and a re-welded kerf almost always mean the wire is too hot, the feed too slow, or both — the foam melts wider than the wire and re-fuses behind it. First lower the temperature and/or speed up the feed so the wire melts a clean gap just ahead of itself and moves on before the edges re-touch.
Keep the wire taut so it does not dwell in one spot, and wipe built-up residue off the cold wire occasionally. If a particular foam is gummy, it may be the wrong material (PU, or a filled foam) — EPS/XPS cut cleanly when heat and feed are balanced. Crisp edges and a thin kerf are the sign you have it right.
Keep the wire taut so it does not dwell in one spot, and wipe built-up residue off the cold wire occasionally. If a particular foam is gummy, it may be the wrong material (PU, or a filled foam) — EPS/XPS cut cleanly when heat and feed are balanced. Crisp edges and a thin kerf are the sign you have it right.