G28 – Return To Machine Home
G28 returns one or more axes to their machine home position after the machine has been homed. Axis values on the same line set an intermediate position the machine moves to first.
Syntax
G28 / G91 G28 Z0
Motion
Rapid speed
You need
Machine homed first
CAUTION
G28 behaves differently in G90 Absolute and G91 Incremental mode, and incorrect use can cause unexpected rapid moves. Take extra care with this command.Parameters
Examples
Rotary axis unwind
G00 A900 (Rapids A to A900 – 2.5 turns) G91 (Incremental mode) G28 A0 (Moves A by 0°, then to A0 within one rotation) G90 (Back to absolute mode)
The A axis unwinds to A0 in less than one revolution, avoiding unnecessary extra turns. With a non-zero value such as G28 A360, the axis first turns a further 360°, then unwinds to A0.
INFORMATION
Without G91, G28 A0 still unwinds within one revolution, but it first moves to the absolute intermediate position A0, which can take many turns. Use G91 with G28 A0 to avoid the extra rotations, whatever the current A coordinate.
