A quick reference for the words that come up everywhere in hot-wire foam cutting and on cncfoam.com.
Cutting terms
- Hot wire — a resistance wire heated by electric current that melts foam.
- Nichrome — a nickel-chromium alloy, the most common hot-wire material; holds tension when hot and resists oxidation.
- Kerf — the width of material removed by the cut. A hot wire melts a kerf slightly wider than the wire itself.
- Feedrate — how fast the wire moves through the foam, usually in mm/s or mm/min. Too fast bends the wire; too slow melts an over-wide kerf.
- Pre-heat / dwell — a short pause at the start of a cut so the wire reaches working temperature before it moves.
- Melt-back — extra foam removed when the wire lingers (e.g. at slow corners), widening the kerf locally.
- Ruled surface — a 3D surface swept by a straight line. A straight hot wire can only ever cut ruled surfaces; that is the key constraint of the whole technique.
- Morph — a cut where the two ends of the wire follow different profiles, blending one cross-section into another (e.g. a tapered wing).
- Indexed rotation — cutting one face, rotating the foam by a set angle, then cutting the next face. Used on 3/5-axis machines.
Machine & CNC terms
- Axis — one direction of controlled motion. Hot-wire machines commonly have 2, 4 or 5 axes plus an optional rotary.
- Kinematics — how a machine's axes map to wire motion (2-axis parallel, 4-axis dual-tower, etc.).
- Tower / gantry — the vertical assembly holding one end of the wire; each tower carries two axes (up/down and front/back).
- G-code — the plain-text command language that tells the machine where to move (see What is G-code?).
- Controller / firmware — the board + software that turns G-code into motor pulses (e.g. ESP32 running FluidNC, Arduino running GRBL).
- FluidNC — modern ESP32 CNC firmware with USB and Wi-Fi, configured by a YAML file.
- GRBL — classic lightweight CNC firmware for Arduino/AVR.
- Stepper motor / driver — the motor that moves an axis and the chip (e.g. TMC2209) that powers it.
- Home / endstop — a known reference position; many hobby foam cutters skip homing and set zero manually.
- Work zero / origin — the (0,0) point your G-code is measured from.
cncfoam.com terms
- Material block — the foam stock you are cutting into, shown as a solid in the viewport.
- Cutter envelope — the machine's maximum reach, shown as the wireframe box.
- Object bar — the top toolbar for scaling, offsetting, rotating and morphing the loaded shape.
- Transport — how the cut leaves the tool: download, USB-serial or Wi-Fi.