Re: [CAD_CAM_EDM_DRO] Lead screw vs. Guide rail clampup

By two bits...

If you're talking about the normal hardened ground rails I imagine the only
downside of rigid fastening at both ends would be thermal
expansion/contraction differences between the rail and bed. A great deal of
"home built" CNC machines would have alloy bases and would have different
thermal characteristics, leading to a slight bending of the rail.

On the other hand, if you're going to be concerned about that type of
effect, you'd probably make your bed out of cast iron anyway, and use ground
linear ways instead of rails. To get the .5% more accuracy in this game you
have to spend 1000's more $.

Cheers, Chris.

* Design engineer, Assembly worker, Cleaner.
* Ohmark Electronics. PO Box 5302, Christchurch, New Zealand.
* http://www.ohmark.co.nz

----- Original Message -----
From: <r_fl_z@...>
To: <CAD_CAM_EDM_DRO@egroups.com>
Sent: Monday, October 23, 2000 10:08 PM
Subject: [CAD_CAM_EDM_DRO] Lead screw vs. Guide rail clampup


> Greets to all:
>
> For a generic stage design, i.e. two guide rails and a stepper driven
> lead screw, is the preferred design to avoid restraining axially at
> least one end of each guide rail? My thinking was that this would
> enhance the accuracy, though perhaps only slightly, by eliminating
> any potential guide rod deformation due to a load induced during
> clamp-up or cutter engagement. Thoughts? Suggestions?
>
>
> Best regards,
>
> Ron
>
>
>
>
>
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