Re: Z axis conversion

Wally:

At 06:18 PM 11/27/00 +0000, you wrote:

>I tend to agree with your "intrinsically crappy situation" statment.
>I keep going around in circles trying to figure out how to power the
>Z axis. All methodes seem to be bad. People that have seen the
>front quill methode of conversion tell me that the attachment screw
>to the quill always comes loose. I would not mind modifing my J head
>if i could come up with a good solution. And i still wonder if
>moving the knee is a good idea or not, in terms of wear. And or
>replacing the acme knee screw with a ball screw.

I'm thinking about this also. I'll get X & Y going then Z, but I'm
still thinking ahead.

I don't see how the screw could come loose from the quill? Any scheme
I think of restricts it from rotating, thus unscrewing.

I've alternately thought of putting a split collar clamp around the bottom of
the quill. A ballscrew mechanism can then be attached to this collar/plate.

The ball screw itself could be attached to this collar/plate. It couldn't
extend below the quill though, so the ballscrew must move up and down with
the quill. If the motor is also mounted on this collar/plate (i.e.
moves with the quill) a timing belt could drive the ballscrew. But if
the motor is mounted on the head, driving the ballscrew gets more complex
as the screw moves axially relative to the motor. One could drive
the ballnut, but the bearings to mount the ballnut would get big.

Alternately, a tube could be mounted to the split collar clamp/plate
extending up alongside the head. The ballnut would be at the top of this
tube and the ballscrew extends down inside it. This moves the ballscrew
mechanism up so it doesn't extend below the quill. The ballscrew is then
mounted with bearings at its top to the head. It would be fixed on only
one end, similar to a bridgeport Y axis. Rotating the screw would drive
the quill up and down. The motor is fixed to the head. However, it may
be difficult to align and maintain alignment of the tube and ballscrew.

You'd only loose half to 3/4 of an inch in quill travel, the thickness of
the collar/plate.

I hope this makes a little sense, I have trouble describing things without
sketches. You can see I also do not have a good solution for this. :-(
Be sure to let me know what you come up with. Thanks.

Hugh Currin
Klamath Falls, OR