Q: For my specific application, I really need long life out of my geared motor. How can I calculate motor life with the following conditions?
1. Motor Part Number: PKP223D15B-SG36-L (PKP series stepper motor with 36:1 SH gear)
2. Speed of Output Shaft: 0.33 Rotations per second
3. Motion – Output shaft cycles back and forth 180 degrees
4. Required torque: 4.5 oz*in
A: Since the load would be handled mostly by the bearing inside the gearhead instead of the motor, the service life of motors will be longer than gearheads. For that reason, we will be basing our life estimation on gearhead life instead of motor bearing life. We have a rated life of 5,000 hours for PKP series SH gears in the catalog based on max conditions, but your requirements are far from max conditions so the life should be much longer.
The following formula calculates the service life of a gearhead:
Where RATED LIFE (L1) = 5000 hours (scroll down below for PKP series SH gear life, or click for full image)
0.33 RPS converts to 19.8 RPM; 19.8 x 36:1 gear ratio = 712.8 RPM input speed at the motor
We will be using a LOAD-TYPE FACTOR of 1.5 for frequent start/stopping via stepper motor.
LIFE IN HOURS = 5000 * (3000/712.8) / [(4.5/56)^3 * 1.5] = 27,037,021.64 hours
If you would like to learn more about life estimation, please click on the following link:
http://www.orientalmotor.com/products/p ... e_Life.pdf
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