Re: [CAD_CAM_EDM_DRO] Re: Re: EMC Lathe mode.

> I THINK that if you only have a single pulse per revolution, it could
> still be workable.
>
> The computer could determine RPM from the single count within a few
> rotations. ( A well written program would wait for a relatively stable
> speed and announce an error if there was too much "wobble". )
>
> From RPM and a single pulse, the CPU could then calculate where the
> spindle is in its rotation.

I really don't like this idea... what happens if the computer gets set
with what it thinks the spindle speed is based on the speed when
cutting air, and then gets really suprised at what happens when the
tool touches the work?

With a really big machine, or a really tight VFD spindle control, one
might get away with this. But neither describes the typical hobby
machine.

I presume the opposition to spindle encoders comes from the difficulty
of mounting. One simple idea is to make a large diameter low
resolution encoder wheel from an overhead transparency using a laser
printer. (hint: postscript is just another cnc language). Stack it
between disks of your favorite easy machining metal and mount on the
back of the spindle. Then you can use discrete phototransistors to
sense it. You may not even need quadrature (ie, you may be able to
assume the direction), but if you do it can by done with two tracks,
or by simply offsetting the sensors.

Chris