lathe g76 feed jerky
Well, I am NOT surprised. The large pulses were exactly what I was expectingThank you Jon
I was able to run halscope and view spindle velocity but was surprised to see the correct dc velocity (rpm) with superimposed large random pulses. These were removed when I switched off the Stepper power supply.
I now know the source of the problem and will now work on it.
My thanks to everybody for your help
Gene
due to your symptoms. And, good to hear that you know what is causing it.
It may be easy or difficult to get rid of the noise pickup, but at least you now
have a simple way to detect the noise issue.
If you have any stepper motor cables that run near the encoder wires, that
would be the first thing to change.
Jon
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John
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Thank you Jon
I was able to run halscope and view spindle velocity but was surprised to see the correct dc velocity (rpm) with superimposed large random pulses.
G76 doesn't use spindle velocity, just spindle position. However these spikes seem to indicate that the encoder is seeing extra pulses. These will give position errors, and inaccurate screw pitch, so need to be removed.
If you did have a B channel then the encoder would be a lot more resilient to noise, as only valid quadrature transitions would be detected. (if there is a spike in A without a B transition, then the encoder will count up by 1 then down by one, not up by two.)
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That is, is feed the raw A and index signals to the debounce inputs and feed the debounce outputs to the encoder counter and then run the debounce comp at the base thread (with a debounce delay of 2 or 3 thread times)
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first. Would a higher resolution encoder allow the program to lock sooner.
Thanks for your help.
Gene
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Probably not. It is a matter of the acceleration specified for the ZThanks for your suggestions re electrical noise. I have rerouted the signal cables away from the stepper cables and added the debounce component with 3 base period delay. The g76 code now cuts perfect pitch threads but I start the thread from 10 mm before the start of the cut. This gives the machine time to stabilise
first. Would a higher resolution encoder allow the program to lock sooner.
Thanks for your help.
Gene
axis and the velocity needed to follow the thread pitch.
You probably do not need 10 mm unless the acceleration
has been set really low. You might want to test by reducing
the length for acceleration, or maybe graphing the velocity of the Z axis
with Halscope to see how long it really takes to accelerate.
Jon
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Try:net spindle-position encoder.0.position => motion.spindle-revs
net spindle-position encoder.0.position-interpolated => motion.spindle-revs
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