RE: [CAD_CAM_EDM_DRO] shaft torsion ?

For the shaft to twist there must be torque applied to it.
Unless your linear bearing assemblies are very draggy, then torque comes
from acceleration.
At cutting speeds with plasma, you just aren't accelerating much.
At rapid speeds you can live with some twisting.
Work it out. I'd be surprised if your worst case error is a significant
percentage of your kerf width
Having said that, 1/2" does seem small.

PK

-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of turbulatordude
Sent: Tuesday, 18 March 2008 8:58 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] shaft torsion ?

Hi all,

5 foot wide gantry on a plasma cutter.

I want to run a shaft across and turn two spur gears on racks.

I am thinking about using 1/2" CRS as the shaft with the servo on it,
but then got to thinking about the shaft twisting.

Another idea is to use 1" OD steel electrical conduit to reduce the
twisting of the shaft.

I don't mind putting bearings along the length to eliminate any
whipping, but the twisting needs to be minimal.

Any ideas ?

Dave


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