I am running Mach4 with G83 Pecking and around 20 holes..
I started with a spot drill around .05 depth..
Looked great till about the 17th hole and then it was drilling down to around .125  and retract was just clearing the top of part.

would that be caused by acceleration or velocity mine seems to be set low acc = 8.0 and v = 60..

Or any other suggestion?..

Thanks gary

Servo or stepper system?

Its a stepper system

I have been thinking to change at least the Z to a closed loop stepper with encoder,

It's doing things fast but if i had to guess it seems that it may be loosing steps when retracting and not on the down, going down is not real fast i have the feed rate slow, but it rapids up fast...

Thanks gary

You may need to tune the acceleration on the Z axis to allow it to ramp up the speed, try halving it and see if that helps, you may be asking it to take the weight of the head too fast.
 

Thanks

I cut it in half, ramps up a lot slower will try to run the code tomorrow and see if i have better luck.

Gary