Homing with gantry and absolute encoders

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21 Jan 2020 14:49 #155324 by mlhilligsoe
I have a gantry setup (XYYZ) with absolute encoders, and need to figure out how to (hopefully avoid to) home the system.

I can manually square the system and store the encoder offset in the encoders themselves, in order to avoid any squaring through linuxcnc.

Right now LinuxCNC (master/devel + Axis) boots into joint mode, and I then have to manually home each joint. Is there a way to avoid this when using absolute encoders?
Also I tried using the HOME_ABSOLUTE_ENCODER configuration setting, but doesn't seem to do anything and I don't know why?

I will upload .hal and .ini files if requested.

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22 Jan 2020 15:59 #155430 by andypugh
HOME_ABSOLUTE_ENCODER works for me, on my lathe.

So, I think we do need to see your INI file.

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15 Apr 2020 13:34 #164060 by jirkam
Good day.
I could join in asking to check my .ini. I don't want to start a new thread.
I have ASDA-A2 with absolute encoders. If I manually move the X axis after switching off, I will load the original position instead of the original position + manual relocation when I turn it on. So I don't know where my mistake is.
Can you advise me?
Thank you very much.
jirka

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15 Apr 2020 13:53 #164062 by dgarrett

... will load the original position instead ...


possibly due to:
[TRAJ]
POSITION_FILE = position.txt

POSITION_FILE = position.txt - If set to a non-empty value,
the joint positions are stored between runs in this file.
This allows the machine to start with the same coordinates
it had on shutdown. This assumes there was no movement of
the machine while powered off. If unset, joint positions are
not stored and will begin at 0 each time LinuxCNC is
started. This can help on smaller machines without home
switches. ...


Ref: linuxcnc.org/docs/2.8/html/config/ini-config.html

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15 Apr 2020 14:38 #164063 by jirkam
Thank you for your response.
If there is no "POSITION_FILE = position.txt", it is always loaded with "X0 Y0 Z0". As if there were no absolute encoders.

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17 Apr 2020 19:40 #164310 by jirkam
Hi
works: net x-pos-fb <= lcec.0.x.enc-pos-enc
i had: net x-pos-fb <= lcec.0.x.enc-pos

Thanks
The following user(s) said Thank You: tommylight

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19 Mar 2021 12:51 #202829 by CNCCustoms
Hi Andy

How does Absolute encoder homing work? Is there a way to show the joint position as a comparison to the absolute encoder all the time (i.e. if I move the motors manually while the machine is off, the position is updated when linuxcnc starts up again?)

My home switches are not fantastically accurate so I would like to make use of the always powered absolute encoders I have on my motors.

I'm running in Step gen and not using closed loop/ velocity mode.

Any help will be greatly appreciated.

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20 Mar 2021 00:03 #202914 by andypugh
If you have absolute encoders then you can home once and then never home again with the right INI config.

Just look for the HOME_ABSOLUTE_ENCODER options here:
linuxcnc.org/docs/2.8/html/config/ini-co...t__lt_num_gt_section

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16 Oct 2021 18:23 #223308 by Marcking
Hi, do you have an ini file as an example of a right INI config for absolute encoders? thanks a lot.

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18 Oct 2021 23:31 #223510 by andypugh
Here is one, but the difference is literally adding a new line in each joint section.
Attachments:

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