Re: Van Norman #12 Milling Machine

At 11:31 PM 1/22/2000 , you wrote:

>From: Jon Elson <jmelson@...>
>

>If you put a ballscrew on the Z (knee) axis, you will almost certainly need
>a power-off brake to keet the knee from crashing to the bottom of
>travel when the power is off, or the system is in e-stop. This may even
>be true with steppers, depending on how much they drag with power
>off. The will also be true on machines where the entire vertical head is
>raised and lowered on a dovetail slide.
>
>Jon
>

On my Rf-45 bed mill/drill the whole head assembly runs up and down on a
dovetail column. To keep it from crashing into the table when the power
goes out I have two sets of gas springs and some heavy duty springs counter
balancing the head. I have sprockets on top of the column and chain
running from the head, over the sprockets and down the back to the springs
and cylinders. It works pretty well. Weights would probably work just as
well.

Dan