While Drilling a Hole in Z axis Mach3 says it is done before reaching bottom

[ZuttyCNC]

I have a old excello 3 axis knee mill - it had a dynapath 10 control orig. - that died 10 years ago - I coverted it over to camsoft with a galil 1730 board
that died 4 weeks ago - it ran on win 98 on a old motherboard with 2 isa slots - one slot was for the galil the other for a board to a opto22 relay board
now have win xp on a old mother board with one isa slot for the galil - now for my problem - i can move and jog all axis - home and limits work
we use featurcam for g-codes and programs - even ran a plastic job just fine - current job is to drill a 3/8 hole in s.s. 1 1/8 deep - as the drill is pecking
down at 5 inches per min. the machine dro and program dro show all the right numbers - but as the drill force builds the feed drops - program finishes
which means the hole is 1 1/8 deep - but it is only 1/2 deep - if i rerun part it will drill a little more out of the hole - during all of this if i watch the dro's
they show correct at all times - even showing the drill tip at 1/2 deep when it thinks it is done - if i dry run the program with no stock it will drill the full
1 1/8 deep - what setting do i need to fix to maintain this lack of movement

bob

[smurph]

Servos or Steppers? 

If steppers, you are losing steps. 

If servos with encoders on the motor, something mechanical is slipping.  For servos, the Galil gets it's feedback from the motor encoders.  If the numbers are right, then the motor shaft went through all of it's paces.  But the screw may not have!  Check your couplings and/or pulleys for slippage on the shafts.

Steve

[ZuttyCNC]

it's a servo system - if I touch off the tool to the top of the stock it is at zero
position on all axis has been maintained - the torque limit is set at max
it's as if the z axis is allowed to lag behind and then catches up

bob

[smurph]

It may indeed be servo lag.  Set the Galil Feature "off on error" and set the following error threshold to something like .100"  If the drive motor trips off, then you need to tighten up your PID loop.

Steve

[HillBilly]

That does sound like servo lag since you are not loosing position. If the machine has performed well with the PID values before you may want to check your motor brushes. A DC servo with more than two brushes does not quit working when a single brush goes out, it gets weaker. I noticed you said the original control was a DynaPath 10, that would be about right for brush life on the Z axis.

Darek