C-Axis (Angular) and sprockets configuration..
03 Feb 2016 13:54 #69511
by andypugh
Replied by andypugh on topic C-Axis (Angular) and sprockets configuration..
If you are using that INI then you are using a scale of 123.
Are you sure that the HAL file is using the correct INI entry?
You don't get 180 degrees. What do you get?
Are you sure that the HAL file is using the correct INI entry?
You don't get 180 degrees. What do you get?
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04 Feb 2016 02:22 #69557
by pkasy
g1 b10 makes 9.0467 degree
Replied by pkasy on topic C-Axis (Angular) and sprockets configuration..
yes, ifAre you sure that the HAL file is using the correct INI entry?
17 float RW 123.8289 stepgen.0.position-scale
if stepgen.0.position-scale=113.5802You don't get 180 degrees. What do you get?
g1 b10 makes 9.0467 degree
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04 Feb 2016 04:32 #69563
by pkasy
Replied by pkasy on topic C-Axis (Angular) and sprockets configuration..
So, the correct answer is 124.583585
exactly at this value error for one revolution is 0.0243 degrees.
exactly at this value error for one revolution is 0.0243 degrees.
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04 Feb 2016 09:12 #69569
by andypugh
How did you determine that number?
These numbers are not random. If you can't explain the SCALE number then something is wrong. (missed steps, slipping coupling).
I could easily believe 127.777777 because that would be right for the very common 90:1 gearing on rotary tables.
Replied by andypugh on topic C-Axis (Angular) and sprockets configuration..
So, the correct answer is 124.583585
exactly at this value error for one revolution is 0.0243 degrees.
How did you determine that number?
These numbers are not random. If you can't explain the SCALE number then something is wrong. (missed steps, slipping coupling).
I could easily believe 127.777777 because that would be right for the very common 90:1 gearing on rotary tables.
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04 Feb 2016 10:11 - 04 Feb 2016 12:10 #69571
by pkasy
Replied by pkasy on topic C-Axis (Angular) and sprockets configuration..
>How did you determine that number?
the exact value I measured by a probe.
I measured the height of the steel bar, clamped to the rotational axis in two places, X1 and X2. rotated 360 degrees axis, again measured with the help of algebra is easy to find the angle between two segments.
then changed in the right direction
halcmd setp stepgen.0.position-scale XXX
and measured again. it was a long, but very accurate.
so now I know the answer with accuracy to 0.0243 per revolution axis.
>These numbers are not random.
I'm in shock
> If you can't explain the SCALE number then something is wrong.
No, I can not.
> (missed steps, slipping coupling).
No. high repeatability, 0.002 mm in height to a radius of 45 mm.
>I could easily believe 127.777777 because that would be right for the very common 90:1 gearing on rotary tables.
label says Harmonic Drive 17-80
this is why I asked - how to calculate the SCALE!
the exact value I measured by a probe.
I measured the height of the steel bar, clamped to the rotational axis in two places, X1 and X2. rotated 360 degrees axis, again measured with the help of algebra is easy to find the angle between two segments.
then changed in the right direction
halcmd setp stepgen.0.position-scale XXX
and measured again. it was a long, but very accurate.
so now I know the answer with accuracy to 0.0243 per revolution axis.
>These numbers are not random.
I'm in shock
> If you can't explain the SCALE number then something is wrong.
No, I can not.
> (missed steps, slipping coupling).
No. high repeatability, 0.002 mm in height to a radius of 45 mm.
>I could easily believe 127.777777 because that would be right for the very common 90:1 gearing on rotary tables.
label says Harmonic Drive 17-80
this is why I asked - how to calculate the SCALE!
Last edit: 04 Feb 2016 12:10 by pkasy.
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04 Feb 2016 11:19 #69572
by andypugh
Replied by andypugh on topic C-Axis (Angular) and sprockets configuration..
Can you carefully count motor revolutions and check that it is exactly 80:1?
I think that, depending on what is held stationary and what is rotating there is more than one potential gear ratio with a harmonic drive.
For example, I think that the rings either have 79 and 81 teeth or 80 and 82 (I have never counted) so depending on which is the static ring you can have 80:1, 78:1 or 82:1 gearing.
Working backwards, and assuming that the pulley tooth counts are right, your number suggests a harmonic drive ratio of 87.75:1
I think that, depending on what is held stationary and what is rotating there is more than one potential gear ratio with a harmonic drive.
For example, I think that the rings either have 79 and 81 teeth or 80 and 82 (I have never counted) so depending on which is the static ring you can have 80:1, 78:1 or 82:1 gearing.
Working backwards, and assuming that the pulley tooth counts are right, your number suggests a harmonic drive ratio of 87.75:1
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04 Feb 2016 12:05 #69573
by pkasy
Replied by pkasy on topic C-Axis (Angular) and sprockets configuration..
>87.75:1
yes, about. but as far as I know, the harmonic gearbox with such a gear ratio does not exist. so the scale must be 124.583333333333
what can affect stepgen.0.position-scale? I saw no source, so I do not know, that can affect the SCALE
maybe something operates within the LinuxCNC?
it is used directly or is there more factors on which it is multiplied or divided?
yes, about. but as far as I know, the harmonic gearbox with such a gear ratio does not exist. so the scale must be 124.583333333333
what can affect stepgen.0.position-scale? I saw no source, so I do not know, that can affect the SCALE
maybe something operates within the LinuxCNC?
it is used directly or is there more factors on which it is multiplied or divided?
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04 Feb 2016 12:27 #69574
by andypugh
Anything you want it to but it would be very unusual indeed to alter it in a running system. It is a pin that you are in control of.
The step generator is sent a new position command every servo cycle (through the stepgen.0.position-cmd pin)
It compares that position command with the current position it has reached (often but not always exactly the same as the previous position-cmd value) then multiplies the difference by the value of the position-scale pin to calculate how many step pulses to send in the next servo period.
Replied by andypugh on topic C-Axis (Angular) and sprockets configuration..
what can affect stepgen.0.position-scale?
Anything you want it to but it would be very unusual indeed to alter it in a running system. It is a pin that you are in control of.
The step generator is sent a new position command every servo cycle (through the stepgen.0.position-cmd pin)
It compares that position command with the current position it has reached (often but not always exactly the same as the previous position-cmd value) then multiplies the difference by the value of the position-scale pin to calculate how many step pulses to send in the next servo period.
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16 Feb 2016 14:00 - 17 Feb 2016 00:38 #70231
by pkasy
Replied by pkasy on topic C-Axis (Angular) and sprockets configuration..
Today I decided to measure more accurately. and got the result -124.5425
This corresponds to the gear ratio - 87.7212391304348![:blink: :blink:](/media/kunena/emoticons/blink.png)
I changed a little bit of height measurement unit from a reputable verser .
I performed a series of tests on the bar clamped in a cartridge.
distance from the center to the measuring point - 82 mm.
measurements were made three times, and then a slow rotation, then three more times.
1th z = 206.881650 mm
2th z = 206.882983 mm,
diff = −0,001333 mm
I have a self-made probe, like renishow. but not so accurate, so why stop there.
Now check the text of test, may be someone will need it.
This corresponds to the gear ratio - 87.7212391304348
![:blink: :blink:](/media/kunena/emoticons/blink.png)
I changed a little bit of height measurement unit from a reputable verser .
I performed a series of tests on the bar clamped in a cartridge.
distance from the center to the measuring point - 82 mm.
measurements were made three times, and then a slow rotation, then three more times.
1th z = 206.881650 mm
2th z = 206.882983 mm,
diff = −0,001333 mm
I have a self-made probe, like renishow. but not so accurate, so why stop there.
Now check the text of test, may be someone will need it.
#<z> = #<_ z> (save current Z position)
G90G1B0F300
G91F50G38.2 Z-50
G0 Z0.5
G4 P0.5
F5G38.2 Z -50
#<Averz> = #5063
G0 Z 0.5
G4 P0.5
G38.2 Z -50
#<Averz> = [#<averz> +#5063]
G0 Z 0.5
G4 P0.5
G38.2 Z -50
#<Averz> = [#<averz> +#5063]
#<Averz> = [#<averz> / 3]
(Print, average z = #<averz>)
G90 G0 Z #<z> (back to start point)
G90G1B360F300
G91F50G38.2 Z-50
G0 Z 0.5
G4 P0.5
F5G38.2 Z -50
#<Averz2> = #5063
G0 Z 0.5
G4 P0.5
G38.2 Z -50
#<Averz2> = [#<averz2> + #5063]
G0 Z 0.5
G4 P0.5
G38.2 Z -50
#<Averz2> = [#<averz2> + #5063]
#<Averz2> = [#<averz2> / 3]
#<Diff> = [#<averz2> - #<averz>]
(Print, average z = #<averz2>, diff = #<diff>)
G90 G0 Z #<z> (back to start point)
M2
Last edit: 17 Feb 2016 00:38 by pkasy. Reason: typo
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25 Jan 2018 13:30 #105001
by pkasy
Replied by pkasy on topic C-Axis (Angular) and sprockets configuration..
Hello.
today the topic received an unexpected continuation.
I removed the stepper motor from this axis and installed a servomotor with an encoder of 2500x4=10000 ppr .
after a series of measurements I came to the conclusion that the gear ratio of this reducer is 112.5.
something like that.
strange, right?
nameplate is 80. not 12.5
I used rawcounts and f-error.
today the topic received an unexpected continuation.
I removed the stepper motor from this axis and installed a servomotor with an encoder of 2500x4=10000 ppr .
after a series of measurements I came to the conclusion that the gear ratio of this reducer is 112.5.
something like that.
strange, right?
nameplate is 80. not 12.5
I used rawcounts and f-error.
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