I have an application where a servomotor is driving a a big cylinder.
After the servomotor there is a planetary gearbox with reduction ratio of 20.
And after the gearbox there is a gear with 20 teeth on a diameter of +- 8 cm that is driving a larger gear on the cylinder with 60 teeth on a diameter of +-25cm.
The inertia of the load compared to the inertia of the motor is about 300:1.
This seems huge but once started, the velocity setpoint always stays the same.
Because we hear some noise and vibration in the gearbox, I have made traces of the motor torque. I see peaks in the motor torque.
When I calculate back the motor speed to the speed a the final gear (60 teeth on cylinder), I get the result that a that motor speed (120rpm) we should have a new tooth of the final gear switch in every 500ms ((120 rpm * 60 teeth)/(60 sec * 60 total reduction ratio)).
I would expect the peaks to happen at intervals that are a multiple of 500ms.
But this isn't exactly the case : for peak to peak times I have f.i. :
1639ms,939ms,768ms,892ms,1191ms,844ms,929ms,725ms.
These are times of consequetive peaks.
Maybe I am fixing too much on the fixed time of 500ms while in reality it is more a continuously process of the teeth getting into each other?
I am also doubting that maybe the distance between the big coarse gear (60 teeth) and the small coarse gear (20 teeth) is not correct enough. What one could expect if the distance between these two gears is too small or too big?
I hope some guys with experience in motion and gearboxes could help me in this difficult problem.
After the servomotor there is a planetary gearbox with reduction ratio of 20.
And after the gearbox there is a gear with 20 teeth on a diameter of +- 8 cm that is driving a larger gear on the cylinder with 60 teeth on a diameter of +-25cm.
The inertia of the load compared to the inertia of the motor is about 300:1.
This seems huge but once started, the velocity setpoint always stays the same.
Because we hear some noise and vibration in the gearbox, I have made traces of the motor torque. I see peaks in the motor torque.
When I calculate back the motor speed to the speed a the final gear (60 teeth on cylinder), I get the result that a that motor speed (120rpm) we should have a new tooth of the final gear switch in every 500ms ((120 rpm * 60 teeth)/(60 sec * 60 total reduction ratio)).
I would expect the peaks to happen at intervals that are a multiple of 500ms.
But this isn't exactly the case : for peak to peak times I have f.i. :
1639ms,939ms,768ms,892ms,1191ms,844ms,929ms,725ms.
These are times of consequetive peaks.
Maybe I am fixing too much on the fixed time of 500ms while in reality it is more a continuously process of the teeth getting into each other?
I am also doubting that maybe the distance between the big coarse gear (60 teeth) and the small coarse gear (20 teeth) is not correct enough. What one could expect if the distance between these two gears is too small or too big?
I hope some guys with experience in motion and gearboxes could help me in this difficult problem.