Hi,

I'm having an issue with Mach3 letting my machine slam into the z-axis limit switch, when fed a G28 line.
The machine has no issue referencing home and returning to zero. Anyone have any ideas as to where the issue may lie (software, hardware, wiring)?

Thanks

Video:
https://www.youtube.com/watch?v=NZhciE4gUUw

a G28 is nothing else then a move to specified home Position (Config->Homing/Limits) in machine coords.

if axis are given with G28 (G28 Z10) it will first move to the given Point and the to specified Position.

i have seen in your Video that you are using:

G91 G28 X0 Y0 Z0 in this case the given values are useless because G91 incremental but distances are 0.

if you have defined Z homepos (Config->Homing/Limits) to 0 it would be the same like G53 Z0

and it Looks like your Z0 is hitting the Limit Switch. you can try to define a -0,2 for Z just for a test.