Change dynamic value of the homing process

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14 Dec 2021 18:25 #229068 by hermann1976
Change dynamic value of the homing process was created by hermann1976
Hello together,

I noticed that the reference travel or homing of the axes is set very hard by the machine dynamics. It seems to me that the axis parameters are not used here. If I then move the axes with jog or the machine runs a program, the axes are moving much more smoothly. Can I set the dynamics for the reference run separately?

Thank you.

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14 Dec 2021 21:56 - 14 Dec 2021 21:56 #229080 by tommylight
Replied by tommylight on topic Change dynamic value of the homing process
In the .ini file:
HOME_SEARCH_VEL = -100.000000
HOME_LATCH_VEL = -5.00000
HOME_FINAL_VEL = 50.000000
Should be easy enough to figure what is what, and the values are in mm, adjust accordingly for inch.
Values are in units/s, so X60 to get the /minute values.
Edit:
Those all need to be set for each joint separately.
Last edit: 14 Dec 2021 21:56 by tommylight. Reason: more info

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15 Dec 2021 11:59 #229115 by hermann1976
Replied by hermann1976 on topic Change dynamic value of the homing process
All of these parameters determine the feed rate of the axes during homing and are known to me.
What I am looking for are the parameters for the acceleration during homing.
It appears that the MAX_ACCELERATION in the [AXIS_n] section has no effect on the homing of the axes.
My machine is very dynamic and drives very hard when homing so that every time I have the feeling that the machine is breaking apart.

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15 Dec 2021 19:30 #229155 by arvidb
Replied by arvidb on topic Change dynamic value of the homing process
This might be a bug in the homing code, or even an intended feature (to stop "immediately" on hitting the home switch).

Can you please post your HAL and INI files, and a detailed description on at which part(s) of the homing process the "tough" dynamics happen? I probably cannot help you currently but it would be useful to have an example of a homing configuration that triggers this behaviour so that I can look into it in the future. I'd love to try to refactor this code to untangle some of the current mess - if I can only find enough time/energy for it!

Besides, if it's a simple config problem you're having then posting your config might allow someone to spot the problem.
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19 Dec 2021 19:26 - 19 Dec 2021 19:30 #229504 by hermann1976
Replied by hermann1976 on topic Change dynamic value of the homing process
Thank you for your answer.

Here are the files of my configuration
for analysis. Maybe you can discover something.

From the point in time when LinuxCNC was started until the end of the home sequence and moving to the home position, it appears that the dynamic settings have no effect. The machine starts and stops very abruptly. In my opinion, the abrupt stop is only necessary if the homing switch is approached to determine the exact position. A slow feed rate is used, on which an abrupt stop making no troubles.

If I then run a program with high feed rates and also with a quick change of direction, I no longer have any problems with the dynamic because the set values ​​are accepted.

I hope you can follow me in my description.
Thank you a lot.
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Last edit: 19 Dec 2021 19:30 by hermann1976.

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19 Dec 2021 21:22 - 19 Dec 2021 21:25 #229509 by arvidb
Replied by arvidb on topic Change dynamic value of the homing process
Have you tried modifying the MAX_ACCELERATION settings in the [JOINT_n] sections? Before the machine is homed it's the joints that are controlled and not the axes. LinuxCNC needs to know the absolute positions of the joints before it can control the axes, to accomodate non-cartesian machines where the mapping joints<->axes may not be trivial.

Since you're saying all movements before homing are very abrupt and after switching to axis control they are okay, I suspect the problem has to do with joints settings. However all your joint MAX_ACCELERATION settings are already equal or lower than the corresponding axis setting, so I don't know what's going on there.
Last edit: 19 Dec 2021 21:25 by arvidb.

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19 Dec 2021 21:48 #229511 by hermann1976
Replied by hermann1976 on topic Change dynamic value of the homing process
Ok, that makes sense.
Could it be that it has to do with this value?
STEPGEN_MAXACCEL = 3125.0

I'll play around with it a bit.
Thank you
 

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19 Dec 2021 22:52 #229521 by arvidb
Replied by arvidb on topic Change dynamic value of the homing process
You're not setting [TRAJ] MAX_LINEAR_ACCELERATION, which means it defaults to 20 in/s² = 508 mm/s². This should limit all axis jogs since it's lower than the individually configured limits. Try to set your [JOINT_n] MAX_ACCELERATION to 500 and see if that fixes things.

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19 Dec 2021 22:54 #229522 by Clive S
Replied by Clive S on topic Change dynamic value of the homing process
You have In the Axis section
# set to double the value in the corresponding joint
MAX_ACCELERATION = 1800.0

and in the joint section
MAX_ACCELERATION = 1800.0 So this should be 900

same for the rest.

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22 Dec 2021 21:08 #229762 by hermann1976
Replied by hermann1976 on topic Change dynamic value of the homing process
It worked now. Many thanks for the help.

Merry Christmas and a Happy New Year.

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