Re: [CAD_CAM_EDM_DRO] CNCing the knee axis...

Kim,
Awhile back, someone posted some photos of a Z axis knee, with a
ballscrew replacing the Acme screw, but in order to keep the knee from
dropping by gravity, he had installed two gas shocks of about 150 lb.
capacity, one on each side of the knee. I've been trying to find the
information, but it's misplaced.

Marv Frankel
Los Angeles

----- Original Message -----
From: "Kim Lux" <lux@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, September 24, 2003 6:17 AM
Subject: [CAD_CAM_EDM_DRO] CNCing the knee axis...


> Hi people.
>
> Has anyone ever CNC'd a BP clone by controlling the knee instead of the
> quill ?
>
> We are about to retrofit a BP clone and are thinking of controlling the
> knee. We've already CNC'd a square column milling machine with a heavy
> head. We counterweighted the head to make it lighter. It works well.
> We are moving it at 100 IPM with ballscrews and Ametek motors, direct
> drive.
>
> Our CNC retrofit would replace the acme screw and 90 degree drive with a
> ballscrew and belt drive. We'd like a 2:1 ratio (motor speed to screw
> speed) to retain some Z axis speed.
>
> I've got two concerns with controlling the knee:
>
> a) does the knee remain square to the machine when not locked ? Ie is
> the knee designed to be an axis feed, ie moved up and down without being
> locked ? (my friend tells me no...) Our mill does not have a gib
> adjustment on the knee.
>
> b) how would one counterweight it ? We used actual weights and a cable
> system to counterweight the head on the square column , but the knee is
> going to be heavier than that head was. I'm thinking of constant
> pressure air cylinders ?
>
> Thanks for your thoughts and advice.
>
>
> --
> Kim Lux <lux@...>
>
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