A servo motor is only as good as the mechanics it drives. The transmission type, the reduction ratio, the inertia match and the coupling decide both the motor size and the dynamics you can reach.
Basics 01
A ball screw gives high precision and high thrust but has a critical-speed and whip limit on long strokes. A belt is economical for fast, long strokes, but its elasticity makes it prone to resonance and lower precision. A rack and pinion is preferred for very long axes and heavy loads, with preloaded or dual-pinion designs used to control backlash.
Servo motor sizingBasics 02
A gearbox divides the load inertia reflected to the motor by the square of the ratio and its torque by the ratio, so a smaller motor can drive a heavier load under control. Choose the ratio so the motor's top speed still covers the load's top speed and the inertia ratio suits the dynamics you need. On precise axes prefer a low-backlash (planetary) gearbox.
Commissioning 03
Servo applications use couplings that are torsionally stiff and free of backlash: bellows and disc couplings are the standard for precise positioning. Jaw couplings with an elastomer insert damp shocks, but their torsional flexibility can cause resonance and lost position. During assembly keep misalignment within the coupling's allowed limit.
Vibration and alarmsBasics 04
On a vertical axis gravity is a continuous load torque: the motor carries it even when the axis is still, and it counts in the RMS calculation. A motor with a brake is needed so the load does not fall when power is lost, and a braking resistor must be planned for the energy returned while moving down. A counterweight or pneumatic balancing noticeably reduces the load on the motor.
Brake timingDrive code, motor, controller and the alarm code you see: with those we reach the right answer faster.
