Re: Rotor inertia.

It's very important. Ideally you want a 1:1 ratio for best rate of
energy transfer though you don't start getting into trouble until the
ratio exceeds 10:1 (load:motor).

Keep in mind the relected moment of inertia decreases with the square
of the motor to load reduction ratio. This means a 4:1 motor to load
reduction gearing gives a 16-fold reduction of load inertia as seen
by the motor.

Sometimes reduction gearing is used for that purpose only, even when
no increase in load torque is needed.

Try an experiment: Attach a bicycle wheel and tire to a step motor or
servo motor 1:1 and try to have the motor turn that load. Not an oz-
in of load torque on the wheel but I'll bet you won't be able to turn
it (more properly, you won't be able to change its speed).

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Jason Cox" <sinergy@o...>
wrote:

> Hello All,
>
> Just wondering when selecting servo motors what impact does rotor

inertia have on the final function of a cnc machine?

>
> From my research motors with a far lower inertia are much cheaper,

but does this really matter. Surely the redution in inertia of the
rotor would be minimal say compared to the inertia of the machine
table.

>
> Thanks for any thoughts.
>
> Regards,
>
> Jason Cox.
>
>
>
>
> [Non-text portions of this message have been removed]