Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo

ballendo wrote:

>2)When a stepper fails, it stops. Stall a stepper and it
>doesn't "care". Often when a servo fails, it runs at top speed as far
>as it can. Until something stops it. Stall a servo, and things burn
>up.(hopefully just a fuse.)
>
>

With proper sensing of abnormal conditions, a servo should not
run away, at least very far, before the problem is detected. The one
case where this can happen is if the encoder loses power, then the
drive has no way to detect that motion is happening. (My analog
servo amps will trip on overcurrent when this happens, though.
The machine moves about 1/4 inch before it estops.)

I assure you I have stalled my servos MANY times, and never even blown
a fuse. It does cause an estop when the axis lags too far behind.

>3) Servos typically require a larger power supply (more amps) than
>steppers(assumes chopper step drives).
>
>

Not necessarily. The peak current might be higher, but the average power
would usually be lower for a milling machine. A router might indeed be
higher. A good size capacitor bank can help buffer those current peaks.

Jon