Index Homing odd offset

Hi,

I'm running ver 2.7.0 pre6 and I'm experiencing an odd offset after homing the Z on my lathe. The machine home has shifted by ~ 3/4"!
I tried to clear any G92 and I don't see any tool offset values in effect.
I'm still in the initial configuration stages and newbee, so I may be doing something wrong.

The Z home index routine worked initially. I have it setup to pull the Z towards a switch, backs off, looks for the index pulse, continues moving past that .025, stops and set machine home to Z0.

This routine changed after I had a joint following error when I was experimenting bumping up the feed in the ini file. I did not change any values in the homing routine.
Homing after the following error caused it to travel away from the index pulse by around 3/4".
I do know that the dro values changed. I jogged the axis when the drives were powered off, resulting in a positional difference that I was expecting to zero back out by homing.

Assuming the motor shaft, encoder and ballscrew alignment didn't change, what causes the machine zero to shift???
As a result, the soft limits are also off.

I need help restoring the original machine home. Thanks!

Are you using the software encoder counter or hardware?

Is it possible that the counter is missing the first index?
Does the offset correspond to any integer multiples of motor revs?

Home position is in absolute coordinates so no G-code offsets should have any effect.

Perhaps try a slower latch velocity as an experiment?

I assume that I'm reading in the index off my encoder on the servo. I can read in the signal, so I think that works. I'm not familiar with the software encoder counter.
Is there a setting in the ini file for that? In case I need to turn it off?
I have the ini file set under axis to HOME_USE_INDEX=YES. The search velocity is at .05, latch velocity at -.030 and final velocity at .030. HOME=0.0, HOME_OFFSET=0.02500
The index seems to trigger at the same spot each homing routine. It just no longer stops where it's supposed to.

I will check to see what the actual travel is to see if it's corresponding to any integer multiples of the motor revs.
If the index signal is not read in, is the motor supposed to stop turning after a few revs?

Not related to the issue, but HOME_SEARCH_VELOCITY would normally be close to rapid speed.

If you are not using the software encoder counter what is counting your encoder pulses?

I wanted to keep the search velocity low as I was not certain what to expect on my initial setup. I may or may not bump it up. Thanks for the heads up.

I'm using the 7i85s and 5i25 from mesa to interface my encoders to linuxcnc.
What is the difference between software and hardware encoder counters? Sorry you got to dumb it down...

OT-CNC wrote: I'm using the 7i85s and 5i25 from mesa to interface my encoders to linuxcnc.
What is the difference between software and hardware encoder counters? Sorry you got to dumb it down...

Mesa encoder counters would be classed as "hardware" so we can discount the possibility of a missed index.

Is your DRO showing absolute position of relative position?

If you issue the command G53 G0 Z0 does the carriage go back to where you expected?