Less than people fear. Foam is soft and the kerf is a fraction of a millimetre wide and slightly fuzzy, so chasing 3D-printer-level precision is wasted effort. Repeatable ±0.3–0.5 mm is plenty for wings, signage and props; the wire's own bow and the foam's skin contribute more error than your steppers will.
What matters far more than micro-resolution is squareness, parallel towers, and a taut wire — geometric setup errors scale across the whole part, while a few microsteps do not. Set sane steps/mm, get the frame square, tension the wire hard, and tune feed-vs-heat. That combination beats an over-built but skewed machine every time.
What matters far more than micro-resolution is squareness, parallel towers, and a taut wire — geometric setup errors scale across the whole part, while a few microsteps do not. Set sane steps/mm, get the frame square, tension the wire hard, and tune feed-vs-heat. That combination beats an over-built but skewed machine every time.