Hi,
is called 'Run From Here' (RFH) and its problematic and given more grief and caused more crashes and gouged work
than any other feature of Mach3. The good news is that if you study it hard enough and practice with it....it will make sense
and is entirely useable.
I'm not sure that ALL of this applies to a plasma table but much will be in common with any mill program.
At any given point in time during a Gcode program your machine will be in a mode, it might be a G1 mode with a feed rate of F,
or it might be in incremental mode with a G51 scale factor and a G68 rotation in action. If you direct Mach to start at any
random Gcode line how is Mach to interpret the Gcode without knowledge of how it got there and what state or mode its in?
When you <Run From Here> Mach will traverse through the program without motion until it arrives at your nominated start
line and thereby have learned what state and mode it is supposed to be in. The next thing it does is a preparatory move
to the location immediately prior to your nominated start point. Mach will move in a direct linear interpolation to that point.
If that point is within the stock volume then its entirely probable you will gouge your work. You are advised to break the preparatory
move into two, first move to the XY location with the tool above the work (safe Z height), THEN move Z to its cutting position
below the work surface.
As I say this applies to a mill but I suspect that much of the thinking behind the procedure is identical to plasma.
Craig