Static Safety Factor
During actual operation, damage may be caused by an unexpectedly large load acting on the crossroller ring that is caused by particularly sudden starting and stopping, vibrations due to a cutting load, or a large moment created by an overhang. Therefore, a static safety factor fS must be considered. The static safety factor fS is obtained from the following formula based on the relationship between the applied load and the basic static load rating. Table 1 shows estimates of the static safety factor.
| fS | Static safety factor (see Table1 ) |
|---|---|
| C0 | Basic static load rating (N) |
| P0 | Static equivalent radial load (N) |
Table 1: Estimates of the Static Safety Factor (fs)
| Load conditions2 | Lower limit of fs |
|---|---|
| Without vibrations or impacts | 2 |
| With vibrations or impacts | 5 |
- 1 The basic static load rating C0 is a static load with a constant direction and size whereby the calculated contact stress of the roller and the raceway at the contact area under maximum stress is 4,000 MPa. (If the contact stress exceeds this level, it will aff ect the rotation.) This load is indicated as C0 in the respective dimensional tables.
- 2 Vibrations and impacts are typically caused by factors such as acceleration and deceleration, sudden starting and stopping, vibrations and impacts from an external machine, and changes in processing power over time.
- 3 The values in the table above are guidelines for minimum static safety factors. However, considering dynamic performance such as service life, we recommend a value of 7 or above.
Static Equivalent Radial Load P0
The static equivalent radial load of the Cross-Roller Ring is obtained from the following equation.
| P0 | Dynamic equivalent radial load (N) |
|---|---|
| Fr | Radial load (N) |
| Fa | Axial load (N) |
| M | Moment (N･mm) |
| X0 | Static radial factor (X0=1) |
| Y0 | Static axial factor (Y0=0.44) |
| dp | Roller pitch circle diameter (mm) |
