Re: [CAD_CAM_EDM_DRO] Re: spinning ball nuts

To: CAD_CAM_EDM_DRO@yahoogroups.com
From: "plastiguy" <plastiguy@...>
Date sent: Sun, 08 Feb 2004 03:24:21 -0000
Subject: [CAD_CAM_EDM_DRO] Re: spinning ball
nuts
Send reply to: CAD_CAM_EDM_DRO@yahoogroups.com
Scott

You might take a look at garage door openers, they are in
the same length as you are considering. The Genie has
the screw in an aluminum extrusion. I haven't tried them, but
picked up some for free.

Bob
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> That "design challenge" will indeed be the "SNAFU"! I still think

you will

> need AT LEAST a 1.25" O.D. screw! I built such a machine in '86
> (126"-"X-screws") and I DID use 1.5"O.D. x ½" pitch ball-screws.

Expensive, yes, but it

> worked!
>

Jan -Thanks for your help. I'm curious why you think still a 1.25"
screw will be needed. This has HUGE load carrying capability, far
more than the couple of hundred pounds tension (at most) load exerted
on it by moving the carriage , even while cutting. Seems all I'll
want to do is have a screw stiff enough to not sag appreciably when
the carriage is at the extreme either end. And even a little sag
would be OK from a positioning perspective, as the screw would be
"lifted" into place as the carriage (a rigid system, much more so than
any sag seen in the screw)passes by. The need for a 1.25" SPINNING
screw comes from the effect of it whipping like a jump rope at high
RPMs if it's not rigid enough (overcome by upping it's diameter as the
unsupported span increases). I will plan on incorporating a
tensioning rig onto one end of the stationary screw (I'll have a VERY
rigid 2"x4" welded steel box beam machine frame) to hopefully find a
good tension that doesn't deform or unduly stretch the screw while
still offering a straight, sag free push-me pull-me system. Again,
thanks for your insight, and please offer me any corrections if I've
misinterpreted or overlooked anything you've offered. To all other
replies to my inquiry, thank you all. I feel much better about this
approcah with the bits and pieces of your collected experiences. Best
Regards - Scott




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