On a 4-axis machine each tower end moves in its own X/Y, so the straight wire is rarely perpendicular to the towers — it tilts as the two ends take different positions. To allow that, mount the wire at each carriage on a small pivot or insulated post so it can swing freely to whatever angle the geometry demands, with the spring keeping it taut through the motion.
Keep the pivot points electrically isolated from the frame, and route the heating current through the wire only (not the structure). The pivot also prevents the wire from being bent or kinked at the ends, which would create a stress point and early breakage.
Keep the pivot points electrically isolated from the frame, and route the heating current through the wire only (not the structure). The pivot also prevents the wire from being bent or kinked at the ends, which would create a stress point and early breakage.