Stepgen spindle w/o encoder feedback - rigid tap.
29 Feb 2016 21:45 #70833
by Hromadka
Stepgen spindle w/o encoder feedback - rigid tap. was created by Hromadka
Hi,
i have converted my 3axis mill DM2800 to LinuxCNC, using Mesa 5i25-7i76.
My spindle is 750W Step/dir AC servo without encoder feedback to the system.
It is setuped with pncconf.
I have no Encoder mounted on the spindle
Is possible to do regular rigid tapping G33.1 with this configuration?
My program stops before the line with G33.1. I believe it is waiting for encoder feedback which is missing.
My idea to link in HAL the Step/dir spindle signals to spindle position system input. PID
But i do not how....
Somehow create Open loop system, i know the syncronisation will be not precise, but since i will have the toolholders with length compensation, it will work...
Thanks for Help
Tom.
i have converted my 3axis mill DM2800 to LinuxCNC, using Mesa 5i25-7i76.
My spindle is 750W Step/dir AC servo without encoder feedback to the system.
It is setuped with pncconf.
I have no Encoder mounted on the spindle
Is possible to do regular rigid tapping G33.1 with this configuration?
My program stops before the line with G33.1. I believe it is waiting for encoder feedback which is missing.
My idea to link in HAL the Step/dir spindle signals to spindle position system input. PID
But i do not how....
Somehow create Open loop system, i know the syncronisation will be not precise, but since i will have the toolholders with length compensation, it will work...
Thanks for Help
Tom.
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29 Feb 2016 23:14 #70837
by andypugh
No, you can't do rigid tapping because the position of the spindle is unknown.
Specifically the system has no way to know when the spindle actually changes direction so that it knows when to change the Z axis direction.
Adding an encoder may not be very difficult, and the 7i76 has an encoder counter for the job.
It _might_ be plausible to use the Hall signals as a surrogate encoder, but I suspect that the resolution would be too coarse.
Replied by andypugh on topic Stepgen spindle w/o encoder feedback - rigid tap.
I have no Encoder mounted on the spindle
Is possible to do regular rigid tapping G33.1 with this configuration?
No, you can't do rigid tapping because the position of the spindle is unknown.
Specifically the system has no way to know when the spindle actually changes direction so that it knows when to change the Z axis direction.
Adding an encoder may not be very difficult, and the 7i76 has an encoder counter for the job.
It _might_ be plausible to use the Hall signals as a surrogate encoder, but I suspect that the resolution would be too coarse.
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29 Feb 2016 23:54 #70838
by cmorley
Replied by cmorley on topic Stepgen spindle w/o encoder feedback - rigid tap.
I believe in principle this would be possible, but I think it would require the mesa card's stepgen to synthesis an encoder/index output. Currently it does not.
maybe it could be calculated with HAL components based on the stepgen position?
Interesting question.
Chris M
maybe it could be calculated with HAL components based on the stepgen position?
Interesting question.
Chris M
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01 Mar 2016 00:46 #70840
by andypugh
This might work for an actual stepper motor drive, but my impression was that the pulse stream was sending velocity commands. If it is actually sending position, then it is possible that the stepgen counts might be usable as position feedback.
I think that a simple custom HAL component could be used to synthesise index-enable and position reset.
Replied by andypugh on topic Stepgen spindle w/o encoder feedback - rigid tap.
I believe in principle this would be possible, but I think it would require the mesa card's stepgen to synthesis an encoder/index output.
This might work for an actual stepper motor drive, but my impression was that the pulse stream was sending velocity commands. If it is actually sending position, then it is possible that the stepgen counts might be usable as position feedback.
I think that a simple custom HAL component could be used to synthesise index-enable and position reset.
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02 Mar 2016 22:30 #70933
by Hromadka
Replied by Hromadka on topic Stepgen spindle w/o encoder feedback - rigid tap.
Hi,
thank you very much for fast feedback, i am really beginner regarding LinuxCNC but in the HAL manual is written
motion.spindle-speed-in - (float, in) Feedback of actual spindle speed in rotations per second. This is used by feed-per-revolution motion (G95). If your spindle encoder driver does not have a velocity output, you can generate a suitable one by sending the spindle position through a ddt component. If you do not have a spindle encoder, you can loop back motion.spindle-speed-out-rps.
I understand this like if i just add a line to my hal
net spindle-vel-fb <= motion.spindle-speed-out-rps
I do not believe it is so simple, have so far no chance to test, my machine is at my parent's house.
My actual HAL follows
# ---setup spindle control signals---
net spindle-vel-cmd-rps <= motion.spindle-speed-out-rps
net spindle-vel-cmd-rps-abs <= motion.spindle-speed-out-rps-abs
net spindle-vel-cmd <= motion.spindle-speed-out
net spindle-vel-cmd-rpm-abs <= motion.spindle-speed-out-abs
net spindle-on <= motion.spindle-on
net spindle-cw <= motion.spindle-forward
net spindle-ccw <= motion.spindle-reverse
net spindle-brake <= motion.spindle-brake
net spindle-revs => motion.spindle-revs
net spindle-at-speed => motion.spindle-at-speed
net spindle-vel-fb => motion.spindle-speed-in
net spindle-index-enable <=> motion.spindle-index-enable
# ---Setup spindle at speed signals---
sets spindle-at-speed true
Regards Tom
thank you very much for fast feedback, i am really beginner regarding LinuxCNC but in the HAL manual is written
motion.spindle-speed-in - (float, in) Feedback of actual spindle speed in rotations per second. This is used by feed-per-revolution motion (G95). If your spindle encoder driver does not have a velocity output, you can generate a suitable one by sending the spindle position through a ddt component. If you do not have a spindle encoder, you can loop back motion.spindle-speed-out-rps.
I understand this like if i just add a line to my hal
net spindle-vel-fb <= motion.spindle-speed-out-rps
I do not believe it is so simple, have so far no chance to test, my machine is at my parent's house.
My actual HAL follows
# ---setup spindle control signals---
net spindle-vel-cmd-rps <= motion.spindle-speed-out-rps
net spindle-vel-cmd-rps-abs <= motion.spindle-speed-out-rps-abs
net spindle-vel-cmd <= motion.spindle-speed-out
net spindle-vel-cmd-rpm-abs <= motion.spindle-speed-out-abs
net spindle-on <= motion.spindle-on
net spindle-cw <= motion.spindle-forward
net spindle-ccw <= motion.spindle-reverse
net spindle-brake <= motion.spindle-brake
net spindle-revs => motion.spindle-revs
net spindle-at-speed => motion.spindle-at-speed
net spindle-vel-fb => motion.spindle-speed-in
net spindle-index-enable <=> motion.spindle-index-enable
# ---Setup spindle at speed signals---
sets spindle-at-speed true
Regards Tom
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02 Mar 2016 22:58 #70935
by andypugh
Replied by andypugh on topic Stepgen spindle w/o encoder feedback - rigid tap.
That's for G95 feed-per-rev
G33.1 rigid tapping (and all threading motion) uses the position feedback in motion.spindle-revs
Also, the motion will not start until spindle.index-enable goes false.
G33.1 rigid tapping (and all threading motion) uses the position feedback in motion.spindle-revs
Also, the motion will not start until spindle.index-enable goes false.
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03 Mar 2016 01:11 #70939
by PCW
Replied by PCW on topic Stepgen spindle w/o encoder feedback - rigid tap.
Probably a emulated index comp that takes position (say stepgen FB position),
mods by one and simulates the index logic would do all thats required
mods by one and simulates the index logic would do all thats required
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