How to jog when beyond soft limits

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18 Jun 2025 17:07 - 18 Jun 2025 17:11 #330459 by kubes
Replied by kubes on topic How to jog when beyond soft limits
Now that you confirm this feature is supported and should work. Which would have been good to know in the first response. I can dig deeper, I assume this is exposed in the hal, correct? Is there a special condition or hal pin for jog while within soft limits? While, there is tons of ductiontation, it is hard to find it when you don't know what you are looking for. If I had to guess, the issue is that it's not a direct EtherCAT issue (has it just a HAL component), but rather a dependency on the configuration from a configuration wizard.

I do agree a machine should never be beyond the limits, but if the logic is just a straight greater than or less than than I think there could be an edge case that needs better logic. Maybe this has already been addressed. I have 23-bit encoders, so that is > 8.3 million per rev. So even with the translation to machine units there is a very very small "error" factor. Meaning the "actual" location will fluctuate (bad word choice) with no movement by this very small amount. This can make the axis and/or joint appear its beyond a soft-limit. For instance, when I zero the DRO will remain "zero" but the "-" will flash on and off. Again, maybe all this has been addressed.

Additionally, I have found incorrect and inaccurate details regarding the setup of absolute encoders and how LCNC handles them in both document and forum searches. I am more than willing to contribute back, but "guidance" would be more helpful.

Lastly, tommylight  Thanks for all your efforts as a moderator; it's a thankless task.
Last edit: 18 Jun 2025 17:11 by kubes.
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18 Jun 2025 18:01 #330461 by tommylight
Replied by tommylight on topic How to jog when beyond soft limits

Additionally, I have found incorrect and inaccurate details regarding the setup of absolute encoders and how LCNC handles them in both document and forum searches.

Yeah search is fuzzy on the forum and utterly useless on google lately.
And this is a rare topic, so not much to go on, but more and more users have similar setups with absolute encoders and homing to index and EtherCAT, mainly due to inrush of cheap china drives with haphazard user manuals leaving users to pretty much figure stuff by trial and error.
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I did a retrofit with absolute encoders, used the "immediate homing" feature in LinuxCNC as it was simpler for them and more in line with their type of "one off" work.
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Did you test adding a bit of HOME_OFFSET? Usually negative values, not always.

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18 Jun 2025 18:22 - 18 Jun 2025 18:23 #330463 by Lcvette
Replied by Lcvette on topic How to jog when beyond soft limits
are you on the soft limit or the hard limit? if the hard limit, then set a home offset so you have a bit of cushion for drift on power cycling. if its a hard limit switch, in probe basic in the side bar tab for "WCS" there is a button for LIIMITS OVERRIDE. this should ignore the limit switch and allow you to jog away. but this isn't really going to fix the issue over all. you should set the home offset with enough distance away from the limit towards the useable axis travel side so it doesn't ever encounter this situation.
Last edit: 18 Jun 2025 18:23 by Lcvette.
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19 Jun 2025 02:35 #330483 by kubes
Replied by kubes on topic How to jog when beyond soft limits
This is just soft-limits as I am using absolute encoders and while I "home" it only sets the axis as homed, there is no travel or switches involved. I may add hard-limit but that is really more of a belts and suspenders solution.

I am not understanding how HOME_OFFSET will fix this for soft-limits. My understanding of HOME_OFFSET my be wrong. but it will offset the home and then the soft-limits will be offset, but I can still jog right to them, and my "little over error" will still be an issue.

Does the LIIMITS OVERRIDES only there for hard limits or will also work for soft-limits?

This all can be just me and my very limited understanding of how to correctly set-up high resolution absolute encores and soft-limits.

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19 Jun 2025 05:18 - 19 Jun 2025 05:20 #330489 by Kieran
Replied by Kieran on topic How to jog when beyond soft limits
On my AXIS gui setup, I can switch to "joint mode" by hitting $ (shift-4)
which lets the servos jog slowly back into the normal travel range. Hit $ again to go back to "world mode" to run as normal from there. Im guessing the other GUI have an easy way to get into joint mode as well. you could also manually turn the ballscrew a little :D
Last edit: 19 Jun 2025 05:20 by Kieran.

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19 Jun 2025 08:47 #330493 by pippin88
Replied by pippin88 on topic How to jog when beyond soft limits
I can see you issue and agree that a better solution is needed for absolute encoder setups.

Maybe two sets of software limits are needed?
Working area
Absolute maximum travel
If machine is within "working area" travel/jogging outside is needed
If machine is outside "working area" but within "absolute maximum travel", then allow jogging. Once within "working area" don't allow jogging/movement back out

Work around:
Move machine off soft limits on shut-down
forum.linuxcnc.org/49-basic-configuratio...tion-shutdown#226443

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