Joint 3 Following error is driving me crazy (2.7 to 2.8 update)

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11 Dec 2020 04:13 #191642 by ccompagnon
Hello,
I'm trying to update LinuxCNC from 2.7 version to 2.8.1 (Debian Buster) version.

i'm running an standard Gantry XXYZ machine with a Mesa 5i25 and a g540 Geckodrive.

I've passed a day configuring .ini file to get the machine homed (I was getting Joint 3 Following error on homing), so I tuned speeds, and now it's homing is OK. (hm2-g540-stepper_2.8.1.hal and 5i25-g540_2.8.1.ini)

When I launched a cutting program again I've got Joint 3 Following error again, with same speeds as in 2.7 version.

Maybe you can help me with configs (I attached 2.7 and 2.8 versions) so I could keep 2.8.1 install.

Thank you very much.

Christian
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11 Dec 2020 12:13 #191661 by tommylight
Stepgen_max_velocity and stepgen_max_acceleration
Must be 25% higher than max_velocity and max_acceleration, they are mostly wrong on both ini files.

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11 Dec 2020 13:37 #191664 by ccompagnon
Thank you Tommylight!
I corrected .ini file in all axis/joints as you said, with no luck :

[AXIS_X]
MIN_LIMIT = -1.0
MAX_LIMIT = 1240.0
MAX_VELOCITY = 100
MAX_ACCELERATION = 40
[JOINT_0]
TYPE = LINEAR
MAX_VELOCITY = 100
MAX_ACCELERATION = 40
STEPGEN_MAX_VEL = 125
STEPGEN_MAX_ACC = 50
BACKLASH = 0.000
SCALE = 22.2222222
...
[JOINT_3]
TYPE = LINEAR
MAX_VELOCITY = 100
MAX_ACCELERATION = 40
STEPGEN_MAX_VEL = 125
STEPGEN_MAX_ACC = 50
BACKLASH = 0.000
SCALE = 22.2222222

I've also lowered speed and accel to from 80% to 20%, no changes.

After homing I run the LinuxCNC axis.ngc file, axis Z moves OK, and then "Joint 3 following error"

I don't understand why it's homing OK, and not moving OK
and why It was working with those speeds on 2.7 and now not working...

Thankyou
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11 Dec 2020 15:17 #191669 by PCW
Your ferror limits in the ini file are too narrow:
FERROR = 0.005
MIN_FERROR = 0.005

Try changing these to

FERROR = 0.1
MIN_FERROR = 0.01

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11 Dec 2020 17:00 #191676 by ccompagnon
Thankyou PCW!

I've changed FERROR = 0.1 and MIN_FERROR = 0.01 on all JOINTS :
I get the same "Joint 3 following error"
I include the .ini file.

I will reinstall 2.7 version so I can mill some jobs.

Christian
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11 Dec 2020 17:31 #191682 by PCW
You must umcomment these lines or a joint 3 following error is guaranteed:

# net motor.03.pos-fb <= hm2_[HOSTMOT2](BOARD).0.stepgen.03.position-fb
# net motor.03.pos-fb => joint.3.motor-pos-fb

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11 Dec 2020 17:46 #191684 by ccompagnon
Thanks PCW!

After uncommenting those lines and I can't Jog the X axis machine, no Homing neither.
I get directly a "Joint 3 following error" when I try to move the axis, or homing.

I appreciate your help.

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11 Dec 2020 18:02 - 11 Dec 2020 18:32 #191686 by PCW
I think what has happened is that the automatic script for updating 2.7 configurations
to 2.8 has failed for your gantry configuration. In fact for a 2.8 configuration, joint 3 hardware
should be driven by LinuxCNCs joint 3 commanded position, not Joint 0 (which is a leftover
from a 2.7 gantry configuration):

net emcmot.03.pos-cmd <= joint.3.motor-pos-cmd
net emcmot.03.pos-cmd => hm2_[HOSTMOT2](BOARD).0.stepgen.03.position-cmd

There are probably more changes needed so beware that you may get bad behaviour
(including racking) before all the needed 2.7 --> 2.8 changes are in place

Can you post the current 2.8 hal and ini files?
Last edit: 11 Dec 2020 18:32 by PCW.

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12 Dec 2020 00:20 #191699 by ccompagnon
Thanks PCW!

Yes, maybe is better to restart a new config from a working gantry 2.8 file.
I confirm the 2.7 version is working without problems.

It's a pitty a software update can break a working configuration.

I share the 2.8 configs.

Christian
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12 Dec 2020 16:15 - 12 Dec 2020 16:17 #191731 by PCW
Can you try with:

# X2 position command from Joint 3
net emcmot.03.pos-cmd <= joint.3.motor-pos-cmd
net emcmot.03.pos-cmd => hm2_[HOSTMOT2](BOARD).0.stepgen.03.position-cmd
Last edit: 12 Dec 2020 16:17 by PCW.

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