http://proma-elektronika.com/index.php/en/tips/plasma-detekcja-materialuthis is using the G31 macro.
G31 Z-100 F300 this lowered the head from wherever it was sitting and stopped when the probe switch closed.
G92 Z0 Set offset to zero.
G00 Z20 This moved the head back up by the amount of float head travel I have.
G92 Z0 Set offset to zero.
G00 Z1 This raised the head a further millimetre.
Here is the g28.1 ex.
G28.1 version
'M3 Macro for TOM G31 Version
Cfr = GetDro(18)
Code"G28.1 Z0 "
While Ismoving()
Wend
Code"G92 Z0"
While Ismoving()
Wend
Code"G0 Z .080" 'Switch offset
While Ismoving()
Wend
Code"G92 Z0.000"
While Ismoving()
Wend
COde" G0 Z0.120" 'Pierce Height
While Ismoving()
Wend
SetDro(18,Cfr)
While Ismoving()
Wend
DoOemButton(110) 'Fires Torch reset THC height
END