Homing with gantry and absolute encoders

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6 years 9 months ago #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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6 years 9 months ago #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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6 years 6 months ago #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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6 years 6 months ago #164062 by dgarrett

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


possibly due to:
Code:
[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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6 years 6 months ago #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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6 years 6 months ago #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

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5 years 7 months ago #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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5 years 7 months ago #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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5 years 2 weeks ago #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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5 years 1 week ago #223510 by andypugh
Here is one, but the difference is literally adding a new line in each joint section.

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