Service Life: Design Life of Motors

The life of Oriental Motor products is an important factor in determining the maintenance and inspection timing of your equipment. This section explains the definition of life for each of our products. Since life is not a guaranteed value, please use it only as a reference for proper maintenance and inspection.

The life of a bearing greatly affects the design life of a motor.
The life of a bearing can be expressed in 2 ways:

①

Grease life is affected by grease deterioration due to heat

②

Mechanical life is affected by rolling fatigue

In most cases, the motor life is estimated based on ① the grease life, since the bearing life is more affected by grease deterioration due to heat generation than the load applied to the bearing.
Temperature is the primary determinant of bearing grease life, meaning that grease life is significantly affected by temperature. A simple representation of this is shown in the graph below.
This graph shows that the life of bearing grease is halved with every 15 °C temperature rise in the bearing.

Taking measures to lower the motor temperature is effective for extending the motor's life.
The table below shows the average bearing grease life for each motor as reference.

• Note that the life of bearing grease is greatly affected by operating conditions, such as method of use and environmental conditions.

AC Motors, Brushless Motors, and Servo Motors

Be sure to keep the surface temperature of the motor case at 90 °C max.

Stepper Motors

Be sure to keep the surface temperature of motor case at 100 °C^* max.

Because of the effects of operating ambient temperature and operating duty, the lower the motor surface temperature, the longer the motor life becomes.
On rare occasions such as when the motor is subjected to a large radial load, the mechanical life may become shorter than the grease life.

• *The AZ Series is 80 °C max., and the PKP Series/PK Series with encoder is 85 °C max.