Turning single axis on and off

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05 May 2026 12:23 #346170 by Ul
Turning single axis on and off was created by Ul
My machine is a small horizontal boring machine with three axis DC servos and lead screws, which I would like to change to ball screws.
If I want to operate the machine manually, I simply turn everything off using the red button in axis (F2), but with ball screws I would need to enable/disable single axis using let's say hardware buttons. Would this be possible?
Currently I am using AXIS 2.9.8 with 7i92.
 

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05 May 2026 15:26 #346175 by PCW
Replied by PCW on topic Turning single axis on and off
I would be possible to disable an axis in hal,, the difficulty is returning to LinuxCNC control
without either generating a following error or a dangerous situation where you get a fast
uncontrolled return to the axis position before the axis was disabled.

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05 May 2026 18:29 #346179 by tommylight
Replied by tommylight on topic Turning single axis on and off
What DC servos? Analog or step/dir like Gecko?

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06 May 2026 19:11 #346218 by Ul
Replied by Ul on topic Turning single axis on and off
Thank you. I've already tried to increase ferror in the ini file to 200mm to deactivate following error completely. I can cut off the motor drivers power supply and turn the handle, but the axis travels back automatically when reactivated. Restarting the program every time is not an option, so I will probably end up building small encoder handwheels using HEDS encoder from Aliexpress. Do handwheels at least work in MDI mode, or do I need to change the tab every time I want to operate it manually?

I am using this kind of driver from Aliexpress: de.aliexpress.com/item/1005009677397224.html
It's wired directly to the 7i92 and it drives small coreless motors with HEDS encoder, so the servo loop is done by the mesa card. No Geckos crawling in my machine.

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06 May 2026 19:39 #346220 by tommylight
Replied by tommylight on topic Turning single axis on and off

...so the servo loop is done by the mesa card.

OK, see PCW's post up.
I think with normal step/drive controlled drives it can be done by disabling the drives as the loop is not closed in LinuxCNC, but i never actually tried it.

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06 May 2026 19:52 #346221 by spumco
Replied by spumco on topic Turning single axis on and off
One way would be to have a hardware (or software) button that sequentially
  • Un-homes the axis
  • Resets the encoder to zero
  • Disconnects the encoder from LCNC
  • Then disables the drive 

Re-enabling it would be:
  • Zero encoder
  • Connect encoder to LCNC
  • Enable drive
  • Re-home axis/joint
This sequence should - I think - take care of the following error problem with no sudden servo movements to 'catch-up' to a massive following error.

LCNC is always disconnected/reconnected to an encoder at zero counts.

NOTE: this process would not be available while running gcode program.  i.e. no stopping in the middle of a program, manually jogging away, and then re-starting the program.

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06 May 2026 21:17 - 06 May 2026 21:19 #346223 by PCW
Replied by PCW on topic Turning single axis on and off
It might also be doable with external offsets, as long as the external offsets
were set back to zero before returning to automatic mode.

(if jogging with a hand wheel in the middle of a program would work for you)
 
Last edit: 06 May 2026 21:19 by PCW.
The following user(s) said Thank You: spumco

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