is lower motor inertia always better on stepper

[smoker]

Hi, I am planning on buying some steppers, but I saw that the motor inertia can be much different from one manufacturer to the other.

Some are double of the others!

So my question, is a lower value always better?

David

[bunalmis]

You must match the motor inertia with load inetia for the maximum power transmition.

Lower motor inertia is good only for free working (no load) motors.

[smoker]

Hi, yes I have read this before.
motor to load inertia should not cross 10:1; but is 5:1 or 1:1 OK?
Or os 1:5 still OK?

Or am I asking things here which would never occur in practice (because the motor inertia is always bigger than gantry)?

How much inertia would a gentry of say 200 kh or 500 lbs have driven by belt (and reduction)? Could somebody give me real examples of their machine?

David

[Al_The_Man]

The sizing programs will give you an idea, the recommended max is usually 10:1
But preferably 5:1 or less, the inertia ratio is reduced by the square of the reduction so reduction brings it down fast.
Acceleration/deceleration is a large factor, as well obviously by the mass of the load and the motor.
Motor inertia should be 1/10th or less than the load inertia.
Al.