Home to index - feeling dumb

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22 Nov 2023 21:11 #286271 by spumco
I'm struggling with homing.  Not quite my first LCNC rodeo, but this is my first attempt at home-to-index and i can't seem to get either axis sorted out.

As it stands, the index pulse is found during homing, but it doesn't look like the DRO is updating with the correct HOME_OFFSET value... causing the axis to overtravel during the final move.

For Z axis (lathe)...here's what I want to happen:
  1. Z moves positive to proxy (located close to hard EoT)
  2. Z moves negative to index
  3. DRO set to Z-2.25" when index triggered
  4. Z moves positive 2.25" and stops
    1. i.e. short of proxy by 0.25"
  5. DRO reads Z0 at final resting point
  6. Max softlimit is Z0
  7. Min softlimit is Z-12
Diagram of the Z-axis.

 

INI values
HOME = 0
HOME_OFFSET = -2.5
HOME_SEARCH_VEL = .1
HOME_LATCH_VEL = -.1
HOME_FINAL_VEL = .1
HOME_IGNORE_LIMITS = YES
HOME_SEQUENCE = 0
HOME_USE_INDEX = YES


PS:
Stumbled across this post:
forum.linuxcnc.org/49-basic-configuratio...ports-on-7i97#282558
that indicated there's been a bug for awhile... did the fix make it to 2.9?
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04 Dec 2023 14:49 #287194 by andypugh
The fix is in 2.9.0 onwards, but not in 2.8.

And I am not sure that it is enough of a bug to prevent it working altogether.

Do you have the joint.N.index-enable pins connected correctly?
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04 Dec 2023 16:04 #287200 by spumco
Replied by spumco on topic Home to index - feeling dumb
@Andy,

The index-enable pins work.  I can see them trip in halshow when the readhead(s) move past them.

Connection in HAL:
net ENC2-INDEX-IN                   <=  hm2_7i96s.0.encoder.02.index-enable
net ENC2-INDEX-IN                   =>  joint.0.index-enable

As I mentioned, LCNC is moving to the final position once the index pulse is triggered.  Problem is that the DRO isn't getting reset to zero when index-enable triggers and so LCNC still 'thinks' that the proximity sensor is zero... not the encoder index.

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04 Dec 2023 17:21 #287205 by PCW
Replied by PCW on topic Home to index - feeling dumb
Hardware wise, what should happen is that the
encoder count should be cleared (to 0) at index detection

I would verify this first
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04 Dec 2023 21:11 #287218 by spumco
Replied by spumco on topic Home to index - feeling dumb
Now the post title is appropriate...

I had the home_offset too large and got confused which direction to calculate from.

Home to index is working now, minus the end-stop crashy part.

Repeats to +/-1 encoder count.  Really need this so I don't have to indicate my subspindle centerline every time I use the lathe.

Thanks gents.

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