Selecting a Motor: Formulas for Calculating Load Torque T_L [N·m] by Drive Mechanism

Formula for Load Torque

Ball Screw Drive

Pulley Drive

Wire and Belt Drive, Rack-and-Pinion Drive

Actual Measurement Method

F

Operation Direction Load [N]

F₀

Preload [N] (≒ 1/3F)

µ₀

Internal Friction Coefficient of Preload Nut (0.1~0.3)

η

Efficiency (0.85~0.95)

i

Speed Reduction Ratio (This is the speed reduction ratio of the mechanism and not the gear ratio of the Oriental Motor's gearhead)

P_B

Ball Screw Lead [m/rev]

F_A

External Force [N]

F_B

Force When Main Shaft Begins to Rotate [N] (F_B = Spring Balance Value [kg] × g [m/s²])

m

Total Mass of Table and Load [kg]

µ

Friction Coefficient of Sliding Surface

θ

Inclination Angle [˚]

D

Final Pulley Diameter [m]

g

Gravitational Acceleration [m/s²] (9.807)