Re: [CAD_CAM_EDM_DRO] CNC lathe question

Keith Clark wrote:

>I am trying to build a CNC controlled router to mount onto a
>woodturning lathe. It will hopefully do shaping but I am also hoping
>for thread operations for barley twists etc. Does it seem reasonable
>to have 2 motors, one variable speed spindle motor for normal lathe
>operations and another stepper motor to do the threading operations?
>Would it be possible to do threading with the variable speed
>controller
>and spindle motor alone. It seems this would require a very accurate
>knowledge of the RPMs to time the travel of the carriage. I am
>thinking that a stepper motor would be accurate enough, but probably
>not turn fast enough for normal lathe operations.
>
>

Given a large enough motor and drive, I think you could rig up a pretty
simple scheme to make the spindle a positioning axis with step/direction
or other control scheme, and at the flip of a spindle relay have it convert
to a speed control scheme. Depending on the size of the lathe, and the
cutting forces involved, a stepper moght be able to handle this. A step/dir
servo could certainly handle it.

Basically, all you need is a circuit (a 555 timer chip would likely do) to
generate step pulses when in the speed mode.

Jon