Static Safety Factor

When using a ball spline, a static safety factor derived from the basic static load rating and the calculated load in each direction must be considered. In particular, if the system starts and stops frequently, or if impact loads are applied, large moment loads or torque caused by overhanging loads may be applied to the system. When selecting a model, make sure that a sufficient static safety factor has been ensured for its maximum load (whether stationary or in motion). In addition, the static safety factor must be confirmed for each load direction using Formulas 9 and 10. For radial loads, you can obtain the static safety factor for the basic static load rating, and for moment loads, you can obtain the static safety factor for the basic static torque rating. Estimates for the static safety factor are shown in Table 7.

fs	Static safety factor
C0T	Basic static torque rating1 （N･m）
C0	Basic static load rating2 （N）
Tmax	Maximum load torque3 （N･m）
Pmax	Maximum applied load3 （N）
fT	Temperature factor （see Predicting the Service Life Fig.1 ）
fC	Contact factor （see Predicting the Service Life Table.8 ）

1 The basic static torque rating is a static torque of a defined direction and size where the sum of the permanent deformation of the ball and that of the raceway at the contact area under maximum stress is 0.0001 times the ball diameter.
2 The basic static load rating is a static load of a defined direction and size where the sum of the permanent deformation of the ball and that of the rolling groove at the contact area under maximum stress is 0.0001 times the ball diameter.
3 The maximum values for T_C and P_C during a travel cycle, as given on Applied Load, are applied to the maximum torque load T_max and the maximum load P_max.

1 In general, factors that cause vibration and impacts include acceleration and deceleration, sudden starts and stops, transmission of vibration and impacts from external devices and machines, and changes in processing force over time.