Servomotors versus Steppermotors

This short article compares servomotors and steppermotors.

Servomotors can achive higher speed than steppers. Steppermotors has a torque curve falling with speed, which means the higher speed the lower torque, servos produce nearly constant torque under cloosed loop in the whole speed range.

Steppers runs in open loop, which means stepper controllers does not have any information about the rotor position, if vibration or overtorque occurs the result can be loosen steps which causes refuse workpieces.

Servos runs in closed loop, the loop is closed with an encoder which provides signals to the controller from the rotor position, if the machine is out of position the controller corrects the error automaticly if possible otherwise stops the work. There are microstepping steppermotor controllers on the market which may cause less vibration, but vibration will never dissapear because it is caused by the construcion of this type of motor therefor there's always a change for loosen steps.

Steppers often has 200 steps/rotation basic resolution, with microstepping resolution can be higher, but microstepping is not accurate enough to calculate with it as a real resolution. Servomotor's resolution depends on the encoders resolution which can be typicaly some*1000counts/revolution.

Steppermotors are brushless and in theory they have no wear parts. Servos have brushes which wears with time, brushes have to be changed after around 5000 hours of heavy work, but their cost is low.

Steppermotors and controllers cost is low compared to servos. Really? Take a look into our webshop!