Re: [CAD_CAM_EDM_DRO] How do you compare steppers to servos

On 26/02/11 01:31, Jeffrey T. Birt wrote:

> There is no 'spring' in a stepper motor. With a stepper motor, with a
> microsteppering drive as you command it to move from microstep to microstep
> the stepper motor will not go 'exactly' to where you tell it; it will be
> within a few microsteps.

Sorry but this is untrue. A stepper works by making the rotor follow a
magnetic field generated by the coils. Magnetic fields are not solid and
behave in a similar way to a spring. You can easily demonstrate the
effect with two magnets. They will attract each other but you can easily
move them closer or further apart. The only thing you can guarantee is
that a stepper will be within +/- 2 full steps of the desired position.
If you exceed two full steps, the motor will jump to the next stable
configuration resulting in lost steps. Microstepping will not improve
this. In fact it makes the issue worse because the resultant magnetic
field can be weaker between full steps.

Les