✍️ Hand-written G-code: learn commands for your hot wire CNC
Basic tutorial · M3 S300 · G90 G91 · G92 X0 Y0 · Cut squares and long lines
🎯 What you'll learn: Communicate directly with your CNC machine by writing G-code commands by hand. Understand M3 S300, F200, G21, G90, G91, and G92 X0 Y0.
📌 Before starting: position the machine at your starting point
⚠️ IMPORTANT (machine type):
- MEDIUM, LARGE, XBIG models (NEMA17 motors): you can move the carriage by hand, motors are free when not powered.
- HOBBY, MINI models (28BYJ-48 motors): CANNOT be moved by hand! They have internal gear reduction. Use only X+/X- / Y+/Y- commands from the software.
- For ALL models: after positioning the wire (with commands or by hand if compatible), use G92 X0 Y0 to set zero.
Step 1: Position the hot wire where you want to start cutting (with commands or by hand, if compatible). Step 2:G92 X0 Y0 — tells the machine: "where I am NOW is zero".
Without G92, the machine uses power-on coordinates. With G92 you start from where you placed the wire.
🧪 Basic code
M3 S300 F200 ; Turn on wire 30%, speed 200 mm/min
G21 ; Millimeters
G90 ; Absolute mode
G92 X0 Y0 ; Zero here
X10 ; 1 cm forward
Y10 ; 1 cm down
X0 ; Back
Y0 ; Up
📋 Commands
Command
What it does
Example
M3 Sxxx
Turn on hot wire (0-1000)
M3 S300 = 30%
Fxxx
Speed mm/min
F200 = 200 mm/min
G21
Set units to mm
G90
Absolute (go to...)
X10 = go to position 10
G91
Incremental (move by...)
X10 = move forward 10
G92 X0 Y0
Set zero here
M5
Turns off the hot wire
M5
📐 Square (video at 4:00)
M3 S300 F200
G21 G90
G92 X0 Y0
X30
Y20
X0
Y0
📏 Long line (video at 7:00)
M3 S300 F300
G21
G91
X260
Y-10
X-260
G90
📌 G90 vs G91: G90 X10 = go to position 10. G91 X10 = move forward 10.