Three settings decide your cut quality: the wire you use, how hot you run it, and how fast you feed it. They interact, so think of them as one system.
Wire material
- Nichrome (NiCr) — the default. High resistance (heats easily from low current), keeps its strength when hot, resists oxidation, and holds tension. Available as Nichrome 60 / 80. Diameters around 0.3–0.5 mm are common.
- Stainless steel — cheaper, lower resistance (needs more current for the same heat), and it softens/stretches more when hot, so it bows more easily. Usable, especially for short wires, but nichrome is worth the upgrade.
Wire diameter
Thinner wire = narrower kerf and finer detail, but it is weaker and bows more easily. Thicker wire is robust and holds tension over long spans but melts a wider kerf and loses fine detail. A common middle ground is ~0.4 mm. cncfoam.com lets you set the wire diameter so the cut-path preview and kerf reasoning match your real wire.
Tension is half the battle
A hot wire expands and goes slack. If it is not kept taut (by a spring, weight, or sprung tower) it will sag, bow and wander, ruining accuracy. Spring-loaded tensioning that pulls the wire tight even as it heats and expands is one of the most important upgrades on any machine.
Setting temperature
You rarely measure wire temperature directly; you tune it by feel. Start cool and raise the power until a scrap of your foam cuts with a thin, clean kerf at your intended feed. Signs you are too hot: wide kerf, rounded edges, lots of smoke, a visibly glowing wire eating foam well ahead of itself. Too cold: the wire drags, bows and stalls. Power is set by the PSU voltage/current or by a PWM duty cycle on the controller.
Setting feedrate
Feedrate (mm/s) is set in the simulator's Cut settings and written into the G-code. Match it to your temperature: hotter wire → faster feed, cooler wire → slower. Denser foam → slower. The cncfoam.com material presets give a sensible starting feed per foam type (e.g. ~35 mm/s for EPS); treat them as a starting point and refine on scrap.
Finding your sweet spot (a recipe)
- Pick a feed from the material preset.
- Cut a straight test line in scrap of your real foam.
- If the wire bows back → lower the feed or raise the heat.
- If the kerf is wide / edges rounded → raise the feed or lower the heat.
- Repeat until the wire stays straight and the kerf is thin. Note the numbers — they will be a good baseline for that foam forever.