Oooooooooooh heres something interesting - when the program fails at the G76 line then it doesn't actually fail in the fact that the steppers do not work - it fails because mach3 fails to go into "mm/rev" mode. it stays in "mm/min" mode, so the steppers are moving but at a really slow rate as it is a 0.75 pitch thread so it's actually doing 0.75mm per minute!

Heres the test g-code.

G18 G21 G64 G80 G90 G40 G49 G94
GO Z50 X50
M0 ( TOOL 05 )
M3 S800
G0 G90 Z5 X9.84
G4 P1000
G76 X8.95 Z-21 Q2 P0.75 J0.03 L45 H0.05 I29 C0.3 B0.01 T0
G80 (CANCEL CANNED CYCLE)
G0 Z50 X50
M30

Any ideas?

thanks

Fixed it - I added "G95" just before the G76 line and it works fine now!

thanks

I have a similar problem, If I stop the program and maybe re-Zero the Z ,that the DRO will sometime run but no stepper movement. I have found if I cycle the E-stop after making a change and then restarting, have not had the problem.  I am using a parallel port. I am new so I maybe doing things that I should not be doing.

That should have been Reset not E-Stop

I found out the G95 trick because someone else had the same problem.