A taut hot wire is a continuous line anchored at both ends, so it cannot plunge into the middle of a block to make a fully enclosed hole the way a laser or router can. Every internal feature needs a lead-in slit from the outside edge to the hole, cut and then (optionally) closed up or hidden.
For letters with counters (O, A, B, e) or parts with windows, plan a slit where it is least visible. https://cncfoam.com's generators and importers handle this by auto-slitting enclosed regions to the edge. If you truly need clean closed holes, you cut the slit, then glue/fill it afterward — there is no way around the basic physics of a stretched wire.
For letters with counters (O, A, B, e) or parts with windows, plan a slit where it is least visible. https://cncfoam.com's generators and importers handle this by auto-slitting enclosed regions to the edge. If you truly need clean closed holes, you cut the slit, then glue/fill it afterward — there is no way around the basic physics of a stretched wire.