If fresh to the topic or if in the know perhaps you can help.

My set up: A controller is connected to Mach3, with the correct pins configured and when the calibrating plate touches the tool the Digitize LED illuminates showing that all is connected well, but the Z axis continues its move for another 20mm or so. Set in mm with probe plate of 3mm

I followed the guru.brew video and script for auto tool zero below and played with some of the variables to little effect on the undesired behaviour

Script:

CurrentFeed = GetOemDRO(818) 'Get the current feedrate to return to later
CurrentAbsInc = GetOemLED(48) 'Get the current G90/G91 state
CurrentGmode = GetOemDRO(819) 'Get the current G0/G1 state

If GetOemLed (825)=0 Then 'Check to see if the probe is already grounded or faulty
DoOEMButton (1010) 'zero the Z axis so the probe move will start from here
Code "G4 P3" ' this delay gives me time to get from computer to hold probe in place
Code "G90 G31Z-20. F30" 'probing move, can set the feed rate here as well as how far to move
While IsMoving() 'wait while it happens
Wend
ZProbePos = GetVar(2002) 'get the exact point the probe was hit
Code "G0 Z" &ZProbePos 'go back to that point, always a very small amount of overrun
While IsMoving ()
Wend
Call SetDro (2, 3) ' change 3mm to your plate thickness and then adjust for final accuracy
Sleep 200 'Pause for Dro to update.
Code "G1 Z1. F50" 'put the Z retract height you want here, must be greater than the touch plate thickness
While IsMoving ()
Wend
Code "(Z axis is now zeroed)" 'puts this message in the status bar
Code "F" &CurrentFeed 'Returns to prior feed rate
Else
Code "(Z-Plate is grounded, check connection and try again)" 'this goes in the status bar if applicable
End If
If CurrentAbsInc = 0 Then 'if G91 was in effect before then return to it
Code "G91"
End If
If CurrentGMode = 0 Then 'if G0 was in effect before then return to it
Code "G0"
End If

I also tried this script:

PlateThickness = GetUserDRO(1151) 'Z-plate thickness DRO

If GetOemLed (825)=0 Then 'Check to see if the probe is already grounded or faulty
DoOEMButton (1010) 'zero the Z axis so the probe move will start from here
Code "G4 P5" ' this delay gives me time to get from computer to hold probe in place
Code "G31Z-40 F500" 'probing move, can set the feed rate here as well as how far to move
While IsMoving() 'wait while it happens
Wend
ZProbePos = GetVar(2002) 'get the axact point the probe was hit
Code "G0 Z" &ZProbePos 'go back to that point, always a very small amount of overrun
While IsMoving ()
Wend
Call SetDro (2, PlateThickness) 'set the Z axis DRO to whatever is set as plate thickness
Code "G4 P0.25" 'Pause for Dro to update.
Code "G0 Z25.4" 'put the Z retract height you want here
Code "(Z axis is now zeroed)" 'puts this message in the status bar
Else
Code "(Z-Plate is grounded, check connection and try again)" 'this goes in the status bar if aplicable
Exit Sub
End If

again with little or no difference

The status window did show Zero Tool Calibration Done, but at +20 or mmm below the true value.

Many thanks for you help

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