Re: [CAD_CAM_EDM_DRO] servo motor ID

Keith Rumley wrote:

> > Now, is this the MOTOR rating, or the servo amp rating? If your servo
> amps
> > can deliver 28 A peak, that should be enough to break your ballnut if
> > there is a belt reduction from the motor.
>
> Motor amps are 230v.3ph. 20a. (the matching FX-490 amps) And no, this isn't
> at home. :)
>
> > If direct drive, it is still a LOT of torque. Is this a standard Series-I
> Bridgeport size machine, or something bigger?
>
> It's a retrofitted Moog - the column is Bridgport I, saddle is similar to
> Series II, but slightly smaller. No reduction belt drive X,Y,Z (Through side
> of saddle). The servos are overkill, but I couldn't refuse them at the price
> I paid. The plan is to put them on a bigger machine later.

Well, as long as you have it directly driven, and keep the current limit on
the servo amp to reasonable values, it should be a very well-performing
system.

> The saddle slows things down - lots of mass. Like you mentioned, belt break
> is at the back of my mind, so I keep EMC limited at the top end of 200ipm on
> the Z. (Interesting note - EMC's commanded IPM is usually higher by two or
> three IPM than that read directly from the drive...)

This is probably a servo tuning issue. I had mine tuned up once so the
commanded and actual velocity lines perfectly overlapped. Due to quantization
errors, the actual line was just a little wider than the commanded, but they
were totally in agreement over a complete move. Now, it DID take me
quite a while to get the tuning perfect. If you have FF1 set to 0.0, you
might try turning it up to about 5.0 and see if this improves performance.

Jon