Missed Servo Moves

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25 Oct 2012 21:07 #25804 by SRT
Missed Servo Moves was created by SRT
Running a part today in our recently retrofitted Turning center. We were about 50 pieces into the run when the turret did not go out to tool change position and decided to change tools right on the part. Basically it just skipped going to G00 X6.0 Z6.0. Any Ideas? Could this be a latency issue? We have run tests and they looked good but maybe this is the every once in a while kind of problem? Running a Foxcon with the Adam chipset. Also running 2.6 PRE

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25 Oct 2012 21:37 #25807 by BigJohnT
Replied by BigJohnT on topic Missed Servo Moves
Your also using the fanuc tool patch? Could be another bug in that... running the bleeding edge is not always smooth.

John

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25 Oct 2012 22:08 #25809 by SRT
Replied by SRT on topic Missed Servo Moves
Understood......I am okay with trying to be progressive. Please understand I am trying to get these configured as close as possible to the other commercial controls I have in my shop, Milacron, Fagor, Fanuc ect....

The Fanuc patch is a must as far as I am concerned in fact I think it should be taken farther simply because the standard is there. I am loving Linux and have already started another retrofit on a larger Turning center I just hope we are not too far ahead of the development of LinuxCNC to continue using it. I don't think we have the knowledge to write patches and help in the process. I don't want to be a thorn but I will continue to ask nicely that more work is done in the tool offset area. Like separate pages for Geometry and Wear offsets, that wear offsets can be entered in Diameter instead of radius and maybe even a GUI that has tabs for both. There has to be other commercial shops that do or will need this to integrate linuxcnc easier into the shop with a format that hired hands can come in and run without too much difference.

I already know that we may have to help in the process, I just hope we can figure out how to help........

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25 Oct 2012 22:55 #25813 by BigJohnT
Replied by BigJohnT on topic Missed Servo Moves
Using patched versions of Master is more help than you can think as you provide feedback to the originator of the patch so they/he/she/it can fix undocumented features in their patch. I don't even know who provided the fanuc patch but if you have the link invite them over here.

John

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26 Oct 2012 21:00 #25845 by andypugh
Replied by andypugh on topic Missed Servo Moves

Running a part today in our recently retrofitted Turning center. We were about 50 pieces into the run when the turret did not go out to tool change position and decided to change tools right on the part.


That sounds messy.

How is the tool-change-request to tool-changed handshake handled?
Is there any chance that you got unlucky with electrical noise?
Maybe a (software) debounce on the status lines is needed?

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27 Oct 2012 02:53 #25849 by PCW
Replied by PCW on topic Missed Servo Moves
It does sound like a possible handshaking problem
(mechanical switch debounce may be an issue as well)
some delays, debouncing and I/O redundancy/sanity checking
might be in order.

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27 Oct 2012 03:04 #25850 by SRT
Replied by SRT on topic Missed Servo Moves
Thanks for the input. I am not too sure exactly what debounce is but I will do some checking on that. I do think that the turret logic was a little suspect, we have put some timers in place to make sure we are reading the proper position and locked into place. I am not 100 percent sure now that any moves were missed and that the turret was just not still turning and searching for the proper tool when the slide was going back into a cut with the second tool. I was not operating it and yesterday I had two people that were sure exactly what happened now I have two people that say maybe that is what happened.

Using Classic Ladder for the Turret logic.

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27 Oct 2012 03:13 #25851 by andypugh
Replied by andypugh on topic Missed Servo Moves

Thanks for the input. I am not too sure exactly what debounce is but I will do some checking on that.

Classically switch bounce is exactly that. as the contacts come together they physically bound and instead of off-on you yet off-on-off-on-off-on…on. Keyboards do it, and hardware/software has to be included to distinguish between bouncing contacts and multiple key presses.
In the case of LinuxCNC there is a "debounce" function that can be set up in HAL and linked to any signals where you absolutely want to make sure that the switch is really on or off. All it does is keep the output the same until is has seen the input hold the same value for a certain number of servo cycles.
I am thinking that perhaps some electrical noise (or even a mechanical vibration) might have set the "tool change finished" signal far too early.

debounce is a slightly odd component to get your head around.
www.linuxcnc.org/docs/html/man/man9/debounce.9.html

You can have multiple channels in multiple groups. Each group can have a different debounce time. Each group needs to be added to a thread separately.

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