Servo -> Gear -> Spindle

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6 years 7 months ago #159496 by Daniel_turning
Servo -> Gear -> Spindle was created by Daniel_turning
Hello there,

First of all sry for my bad english.

Back in the days I was designing my cnclathe, I think I was super smart. *irony*
I want to use a ac-servo-motor hook up to the spindle. Using timing belts with pullys 48:32 to get more speed on the spindle.

Now I have build everthing up and notice that I am not able to synchronize the spindle.
The velocity of the servo-encoder is 1.5 slower than the spindle. Same problem with the index signal. :)

Now I am asking me, can I solve this issue with linuxcnc software encoder or linuxcnc sofware gearchange?
Or is it not worth it and should I change pullys to 1:1 ratio?

Kind regards
Daniel

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6 years 7 months ago #159499 by cmorley
Replied by cmorley on topic Servo -> Gear -> Spindle
Can you add an encoder or an index to the spindle shaft?

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6 years 7 months ago #159513 by Daniel_turning
Replied by Daniel_turning on topic Servo -> Gear -> Spindle
I think that should be possible!

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6 years 7 months ago #159542 by andypugh
Replied by andypugh on topic Servo -> Gear -> Spindle

Daniel_turning wrote: Now I am asking me, can I solve this issue with linuxcnc software encoder or linuxcnc sofware gearchange?
Or is it not worth it and should I change pullys to 1:1 ratio?


The best answer might be to add an index flag of some sort to the actual spindle and use that as the spindle index.
You can continue to use the A and B phases from the motor encoder, with the scale corrected to allow for the gearing.
The index could be anything, such as a proximity sensor detecting a keyway or a reflective opto-sensor detecting a target on a drive pulley.

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6 years 7 months ago #159679 by Daniel_turning
Replied by Daniel_turning on topic Servo -> Gear -> Spindle
Thank you both for your information.

Today I take a look at my machine. Unfortunatly I don't have enougth space for another pully on the spindle shaft.
So I have to struggle witch A and B phase from servo and add seconde index signal.

So if I am using A and B phase from servoencoder I have to use Linuxcnc-software-encoder module?

somethink like?
Code:
loadrt encoder num_chan =1; addf encoder.update-counters base-thread addf encoder.capture-position servo-thread setp encoder.0.position-scale 6666.66 #servo-encoder counts 10.000 units/rev == spindle turns 1.5 times more # set the HAL encoder to quadrature counting using A and B. setp encoder.0.counter-mode false # connect the HAL encoder outputs to LinuxCNC. net spindle-position encoder.0.position => motion.spindle-revs net spindle-velocity encoder.0.velocity => motion.spindle-speed-in net spindle-index-enable encoder.0.index-enable <=> motion.spindle-index-enable # connect the HAL encoder inputs to the real encoder. net spindle-phase-a encoder.0.phase-A <= myMesaPin.xy.fromServoEncoder net spindle-phase-b encoder.0.phase-B <= myMesaPin.xy.fromServoEncoder net spindle-index encoder.0.phase-Z <= myMesaPin.xy.fromSecondeIndexSource

Is that the right way to get lucky?

Kind regards
Daniel

By the way, thanks for your time!

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6 years 7 months ago #159681 by PCW
Replied by PCW on topic Servo -> Gear -> Spindle
You can use a hardware encoder with a independent index source
The only disadvantages I can think of (which also apply to the software
encoder)
are:

1. The index is not synchronized with A or B so you may have a count or so
of uncertainly in index position. You might be able to adjust the index sensor
so index is in sync with counts on a low resolution encoder where a 1 count uncertainty matters.

2. The index is likely to be wider than 1 count so the index position will be
different depending on direction. I don't think this makes any practical difference to LinuxCNC.

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6 years 7 months ago #159688 by andypugh
Replied by andypugh on topic Servo -> Gear -> Spindle
My suggestion for an index would be to drill a hole in one of the spindle pulley flanges and then mount an opto-sensor (fork / slot type) in the area where the belt is not wrapped round the pulley.

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6 years 7 months ago #159692 by Daniel_turning
Replied by Daniel_turning on topic Servo -> Gear -> Spindle
I will try it. Thank you

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6 years 6 months ago #162749 by Daniel_turning
Replied by Daniel_turning on topic Servo -> Gear -> Spindle
Hello,

I tinker around and put another pully on the spindle shaft.
Now I have a new 2000 line encoder hooked up 1:1 to the spindle shaft. Not beautiful but it seems to works.

Thanks for your help!

Kind regards
Daniel

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6 years 6 months ago #162810 by tommylight
Replied by tommylight on topic Servo -> Gear -> Spindle
Nice work.

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