Understanding G-code Variations in Hobby CNC
While G-code is the universal language of CNC machines, not all "dialects" are the same. If you are moving from a standard industrial machine to a hobbyist desktop CNC, you might encounter some unexpected behaviors.
1. The Homing and Coordinate System (G28 vs G54)
In many hobbyist controllers like GRBL, the way machines handle machine zero versus work zero can differ from industrial standards.
; Standard Industrial / Fanuc style
G28 X0 Y0 Z0 ; Home all axes
G54 ; Select Work Coordinate System 1
G0 X10 Y10 ; Move to WCS 10,10
; Hobbyist (GRBL/Marlin)
$H ; GRBL specific homing command
G92 X0 Y0 Z0 ; Often used in hobby CNC to manually set "Zero" at current position
2. Canned Cycles (G81, G83)
One of the biggest differences is the support for Canned Cycles. Most professional CNCs use G81 for drilling, but many hobbyist boards (especially basic GRBL setups) do not support them.
; Professional CNC (Canned Cycle)
G81 R5 Z-10 F100 ; Simple drill cycle, retract to 5mm, depth -10mm
; Hobbyist CNC (Manual Expansion)
; Since G81 is often unsupported, you must write:
G0 Z5
G1 Z-10 F100
G0 Z5
3. Spindle and Coolant Control (M3, M8)
In hobby CNCs, M-codes depend heavily on how you wired your controller (e.g., Arduino/RAMPS).
M3/M5: Spindle On/Off (Standard across almost all).
M8/M9: Coolant control (Commonly used to trigger a vacuum or relay in hobby setups).
