Re: [CAD_CAM_EDM_DRO] Servo Encoders vs Steppers

Carol & Jerry Jankura wrote:

>>I can see that any motor with an encoder would offer much higher
>>positional accuracy, but since there are so many machines without it,
>>I don't think it matters for many of them.
>>
>>
>Actually, there's a limit to positional error there also. Servos have a
>dead band in which they won't move even if the table moves. One of the
>settings of a servo amplifier has to do with setting that dead band. If
>you set it too large, you can have large positional errors. If you set
>it too small, the servo will continually hunt back and forward (CW and
>CCW motion) looking for the deadband.
>
>
>

With a sufficiently high encoder resolution, the deadband can be quite
small. I
usually have it set at just a couple of encoder counts. At 128,000
counts/inch,
the deadband I use is around .000025"

Jon