Efficiency

The natural rolling resistance in the contact areas of rolling elements is an unavoidable loss. Therefore, the actual efficiency η_a is always slightly less than 100%.

η_a = tan φtan (φ+ρ)

Transformation of a torque into an axial force

η'_a = tan (φ-ρ)tan φ

Transformation of an axial force into a back torque

Factors Determining the Angle of Friction

Manufacturer's Specific Features

Form of ball tracks - Track geometry of screw and nut
Manufacturing accuracy - Level of machining precision
Surface hardness - Hardness of screw and nut
Surface quality - Surface treatment of ball tracks
Recirculating system - Ball return design

Users' Operation Data

Axial load and acceleration - Applied forces and dynamic conditions
Lubrication - Lubricant type and condition
Number of rotation - Operating speed
Mounting accuracy - Alignment of screw and nut

Practical Efficiency and Operating Temperature

Under operating conditions, the axial load F_a may be several times the nut preload F_pr. Therefore, the manufacturer's specific features have a significant impact on the actual efficiency η_a. The effect of efficiency on operating temperature can be seen from the chart.

Angle of Friction for AM Ball Screws

After adjusting nut preload and the resulting axial rigidity, the angle of friction ρ for AM ball screws is approximately 0.2 degrees

Efficiency and Operating Temperature Relationship Chart

Effect of efficiency on operating temperature

Driving Torque

Transformation of a torque M_a into an axial force F_a

M_a = F_a · P2000 · π · η_a

Transformation of an axial force F_a into a back torque M_e

M_e = F_a · P · η'_a2000 · π

F_a-Axial load[N]

P-Lead/pitch[mm]

φ-Angle of lead[degree]

ρ-Angle of friction[degree]

η_a-Real value of efficiency

η'_a-Real value of efficiency

M_a-Driving torque[Nm]

M_e-Back torque[Nm]