2.3.5 Stick Slip
When using an extra-long conveyor system (more than 15 m) and slow chain speed (less than 10 m/min.), you may notice longitudinal vibration in the line, which is called stick slip, or jerking.
The basis for this phenomenon can be seen in Figure 2.24. Here the coefficient of friction is plotted against the speed of the chain. When operating a long conveyor at slow speeds, the coefficient of friction for sliding surfaces (in top chains, between top plates and rails; in R-rollers, between the outer surface of the bushing and inner surface of the roller) decreases as speed increases. This causes the chain to jerk or stick slip.
Usually, you can't solve this problem by adding lubrication or by increasing the number of sprocket teeth. There are, however, things you can do to prevent or reduce stick slip:
- Increase chain speed.
Figure 2.24 How Chain Speed Impacts the Friction Coefficient
- Eliminate or decrease the decline in the coefficient of friction by using a bearing roller (please consult with manufacturer if the speed is less than 2 m/min.), or use a special kind of lubrication oil (Tsubaki special oil, or others).
- Increase chain rigidity (AE). A is the chain's section area, and E is Young's modulus. To increase AE, use a larger chain. If there are several chains with the same allowable tension, choose the one with the thicker plate.
- Separate the conveyor into sections and reduce the length of each machine.
If stick slip continues to be a problem, consult the equipment manufacturer.