Stepgen spindle

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13 Aug 2022 12:21 #249643 by gilesclement
Stepgen spindle was created by gilesclement
Hey folks, longtime listener, first time caller.I have a small 3 axis mill which I've built, for the spindle I'm using a 1kw servo motor with a 94 tooth pulley stepping down to a 40 tooth pulley on the spindle. I've been trying to set this up as Stepgen controlled but the speed of the spindle is being limited. I'm a bit of a luddite when it comes to this and was hoping someone might be able to give me some idea of what my settings should be. I'm confused by how the top two figures come out of pncconf as low numbers the max_velocity and max_accel are usually 50ish or less after I open the ini file which then makes the servo rotate verrrrry slowly. 

The servo has a max rpm of 3000 so my final spindle speed should be 7050. Currently the tach on the servo driver shows that I'm getting 1190rpm but it won't go higher than that. 

- Should it be possible to run a Stepgen spindle at 3000rpm? 
- Is there any advantage to running an analog output instead? Thanks for any help, Giles 
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13 Aug 2022 12:47 #249647 by cmorley
Replied by cmorley on topic Stepgen spindle
I know how axis the ini settings are in revs per second rather then minute.
I bet pncconfcsets thecspindlecascrevsxper second too. 50 rps is 3000 rpm

P setting seems wrong to me for stepper. Shpuld be Like 1000 or so.
Peter could give you better advice there.
Also what mixrocsteos is the driver set to?

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13 Aug 2022 16:23 #249655 by PCW
Replied by PCW on topic Stepgen spindle
Actually, for a step/dir driven spindle I would set P to 0.
The FF0=1 will forward the commanded spindle speed
directly to the stepgen velocity.

If you set the stepscale to 1/60 the steps per turn of the spindle, the spindle
will be scaled directly in RPM.
The following user(s) said Thank You: joekline9

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17 Aug 2022 16:08 #249954 by gilesclement
Replied by gilesclement on topic Stepgen spindle
So I did more looking into the servo driver and found that the factory settings for the steps/rotation were set at 10k. Same for the encoder. Could that explain why I was getting much slower than expected rpms out of the motor?

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17 Aug 2022 16:26 #249957 by PCW
Replied by PCW on topic Stepgen spindle
Pretty hard to guess...

can you post your hal and ini files?

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17 Aug 2022 21:23 #249974 by gilesclement
Replied by gilesclement on topic Stepgen spindle
Thanks, so here is a google drive with the Hal and ini files.drive.google.com/drive/folders/1m6BoVFtY...yYu1d4vq?usp=sharing

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18 Aug 2022 03:42 - 18 Aug 2022 03:43 #249997 by PCW
Replied by PCW on topic Stepgen spindle
[SPINDLE_0]
MAX_VELOCITY = 104.16666666666667
MAX_ACCELERATION = 400.0
# The values below should be 25% larger than MAX_VELOCITY and MAX_ACCELERATION
# If using BACKLASH compensation STEPGEN_MAXACCEL should be 100% larger.
STEPGEN_MAXVEL = 130.21
STEPGEN_MAXACCEL = 500.00
P = 100.0   <<<<<<<<<<<<<<<<< I would set this to 0 and not worry about encoder feedback yet
I = 0.0
D = 0.0
FF0 = 1.0
FF1 = 0.0
FF2 = 0.0
BIAS = 0.0
DEADBAND = 0.0
MAX_OUTPUT = 4700.0
ENCODER_SCALE = 1000.0 <<<<<<<<<<<<<<<<<<<<< if you have 10000 counts per turn, this must be 10000
# these are in nanoseconds
DIRSETUP   = 5000
DIRHOLD    = 5000
STEPLEN    = 2500
STEPSPACE  = 2500
STEP_SCALE = 1000.0  <<<<<<<<<<<<<<<<<<<<< if you have 10000 steps per turn, this must be 10000
Last edit: 18 Aug 2022 03:43 by PCW.

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18 Aug 2022 12:26 #250013 by gilesclement
Replied by gilesclement on topic Stepgen spindle
Ok, thank you. The Max_Output would then be the maximum speed of the motor (3000rpm) or the max speed of the spindle after the pulley ratio?

And will Max acceleration also control deceleration?

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18 Aug 2022 13:52 #250018 by PCW
Replied by PCW on topic Stepgen spindle
All speed settings should be for the output at the spindle so instead of 10000
for the step scale, it should be 10000*motor_speed/spindle_speed

The stepgen acceleration settings will determine the spindle ramp rate
(in RPS/S)

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