Re: Servo as a Sherline spindle motor ?

> One thing I'd like to try on the Sherline is CNC threading.
>
> I see two ways to do this.
>
> 1. Put a servo on the spindle and write a bit of custom code; no

real problem, or

>
> 2. Put a nice fat motor on the spindle (so there's no worries about

it slowing down) and use one of the "spindle sensor" options.

The Sherline spindle is fine for threading. Our SYS-3A servo systems
are used a lot for this purpose. The system uses a quadrature encoder
to sense the spindle position with a resolution of 2000 counts per
rev. The spindle is electronically geared to the axis drive servo
motors. This permits the operator to make heavy cuts, lug down the
spindle, and still mantain accurate position in the cut. I have cut
1/2-13 threads in soft steel in "high gear" pulley setting. I would
not recommend trying to cut threads any coarser than this as the tool
posts and machien frame are designed for 1/4 shank tools and they
don't do too well with the heavier cuts needed for more coarse
threading.

This system uses DeskCNC software with controller board to eliminate
the problems with thread accuracy on other software-only based
options.

Fred Smith - IMService
http://www.imsrv.com