Re: [CAD_CAM_EDM_DRO] More about motors?

Gordon Robertson wrote:

> Can anyone tell me the differences between stepper motors and servo
> motors? Or are these the same "animals" with different names?

Absolutely different. Stepper motors are generally constructed with
permanent magnets in the rotor, and many field poles in the stator.
When power is applied, the stator windings attract the rotor magnets,
and make the motor move a very small diistance. Common motors used
in positioning systems have 200 steps per revolution.

Servo motors come in several varieties, DC brush is the oldest, and later
types are DC brushless and AC flux-vector. These motors are designed
to operate over a wider range of speeds than steppers, and are capable
of extremely smooth motion even at low speeds in closed-loop servo
drive systems. They are generally capable of much higher torque/power
per volume and size than steppers.

> If different, then what are the advantages/disadvantages of using one
> or the other?

Servo motors are capable of higher speeds than steppers in most cases.
More power and torque are available from servo motors for the same
size and weight. Servo motors generally run much cooler than steppers.
More precise motion can be obtained from a servo system.

On the other hand, open-loop positioning systems can be made extremely
cheaply with steppers, at the expense of lower speeds, less precision
and the possibility of losing steps.

Jon