Re: [CAD_CAM_EDM_DRO] re:Cnc router help

Ballendo, I presume your idea is to fix the ends of the ball screw (or at
least one end anyway) when spinning the ball nut. How are you spinning the
ball nut? (I'm enquiring about the mechanical connection here as it would
appear the drive motor will either need to travel along with the nut or some
sort of long floating driveshaft will be required.)

Smoke
-----Original Message-----
From: ballendo@... <ballendo@...>
To: CAD_CAM_EDM_DRO@yahoogroups.com <CAD_CAM_EDM_DRO@yahoogroups.com>
Date: Monday, January 29, 2001 3:50 PM
Subject: [CAD_CAM_EDM_DRO] re:Cnc router help

>Wilfrid,
>
>I think you are going to have problems with a 3/4 ballscrew eight
>feet long... I would spin the ballnut and mount the ballscrew in
>tension (slightly) This eliminates the need to machine the ends of
>the long screw, and will greatly reduce resonance and shaft
>compression load factors (you will need a solid structure to attach
>the ends to, as you are trying to create a 'tension' load instead of
>a compression load.)
>
>The 3/4 by five foot might be okay with good endmounts. Here I'd
>suggest at least one RIGID style end mount, maybe both. Depends on
>the speed you're hoping to achieve.
>
>As Les said, be sure to use the mfr tables for ballscrew selection!
>They know what they're doing!
>
>Lastly, did I understand you are going to have a 3 foot Z axis!!? Be
>careful here! The moment loads (especially on a gantry style machine)
>add up quickly! Most people don't REALLY NEED the "large Z axis
>travel they think they do... Especially since it often costs so much
>in machine stiffness, which is felt at ALL positions...
>I suggest the shortest Z you can "get away with", and a move-able
>bridge or table structure...
>
>Hope this helps.
>
>Ballendo
>
>>As for the lengths- 66 and particularly 96x.75 ballscrews will
>>have very low critical speeds and safe compression loads.
><s>Please review the thomson design tables in the catalog or on line
>>at their web site.
>
>
>
>
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