Re: [CAD_CAM_EDM_DRO] Re: Moog makes it home

> Getting back to mounting the x ballscrew, it looks like the table is
> small compared to the saddle, and I suspect it would be difficult to
> get even close to that long travel by mounting the screw to the
> table, correct? (I still think it's incredible that you were able to
> nearly double the x axis travel) So using a cog belt and tucking the
> servo underneath clearly makes sense seen in that light. Wouldn't it
> make sense to just eliminate the side extensions on the saddle as

I used Bridgeport clone end cap bearing supports turned upside down, mounted
to the ends of the table for the X. Then did just what you described - used
cogged belt and put the servo under the table. The side extensions are off.
I'd go with plate mounts on the ends, as you could put a more consistent
tension on the ballscrew.

There are 48" of ballscrew thread, less 8" or so of preloaded nut = 40",
less a little for clearance at the ends, leaves 38" of travel. The table is
30", so it extends past the saddle edge the length of the table less half
table length, and less half of the nut length. So 30" less 15", less 4" =
11" unsupported, leaving 19" in the saddle. Most of the time the table never
leaves the saddle, except the homing cycle on startup.

> that face. What I was thinking was to just whack off that 2" and
> drill that piece for the nut support, then use a plate for the
> bearing support and servo mount, tucking the servo under the saddle
> either to the right or the left, wherever the x servo isn't.

I dropped my servo directly underneath the knee. Take care to note the
available belt sizes, though. I tried to take my measurements too closely,
and ended up having to grind a groove in the underside of the knee, because
the back end of my servo just touched it when the belt was tightened.

I replaced the screw riser post with a taller one, and added a 4" sleave
riser to accomodate the preloaded nut. (wasted money, there, as the ball
bearing in the knee isn't pre-loaded) I was going to replace the existing
knee ball bearing, but due to the method of driving the screw from just
outside the knee, I ran out of space to do the bearings. In practice the
knee weight does a good job.

> Who
> knows, there could even be room enough to put it inside the knee,
> but I doubt my servos are small enough for that.

Right, there. The inside of the knee is essentially the same as a
Bridgeport - support ribs all over, and the remaining space needed for the
nut & screw. It is quite oily in there.

I don't have a digital camera handy, otherwise I'd put some pictures up for
you. (That might be a good excuse, too, as it isn't inherently pretty. :)

- Keith