Run inflexible during working
1. Lacking of grease
2. There is impurity in raceway as the Sealing strip breakage（Such as, bad working condition and dust in raceway ）
3. Gear meshing is not very well, impurity or gear broken.
1. Fill grease as the requirements.
2. Change the sealing strip
3. Checking the gear meshing to see whether there is sundries or gear broken.