Avoid Poor Cut Surfaces in Hot Wire Cutting

With EPS and Styrofoam, damp material is by far the most common cause of rough cut surfaces. The hot wire evaporates the trapped moisture suddenly – the resulting steam bubbles leave an irregular rough surface. This cannot be resolved with any setting. Solution: allow the block to dry sufficiently. Allow freshly produced EPS blocks at least 48 hours to dry, and longer for blocks that have been stored in damp conditions. A simple test: cut a thin slice and observe the cut surface – if it steams slightly, the material is still too damp.

Thread pulling with XPS and Styrodur is a classic problem – particularly common in sign-making when a very small cutting gap is desired. The cause: wire temperature is too low. The wire does not cleanly melt the material away but smears along it – fine threads form on the cut surface. Solution: increase temperature until the cutting gap is consistently approx. 2 mm. Very fresh or very damp XPS is a special case – it cannot be cut cleanly at all and must first dry sufficiently.

An old cutting wire becomes permanently longer over time. Eventually the spring travel is no longer sufficient to compensate the length change – the wire sags, vibrates in the material or smears on the surface. The result is irregular surfaces that appear despite correct settings. Wrong springs can have the same effect if they cannot absorb the wire length change during cutting. Solution: replace the wire and ensure the correct spring for the application. Wire replacement on cnc-multitool machines is tool-free – quick and simple.