Re: [CAD_CAM_EDM_DRO] Positioning

On Wed, 11 Jun 2014 01:11:23 -0400, you wrote:

>Let's look at your points in order:
>
>Thermal expansion should not affect backlash, it should affect
>positional accuracy. Since backlash is clearance or lost motion in a
>mechanism caused by gaps between the parts, and such lost motion is
>possible to eliminate, thermal expansion may or may not matter. The
>joint may not be rigid, but that is another matter.

What other matter? There has to be some free space to allow for initial
thermal expansion in the joint as it warms up during use, and still some
left to allow the surfaces to move. No space, no move.

>Rolling and sliding friction can cause backlash, it is true, but that
>assumes material contact. Magnetic suspension in a vacuum does not have
>rolling or sliding friction. It may not be practical for your
>operation, but it exists.

What Vacuum - we are talking about machine ballscrews, not some fantasy
sci fi set in space?

>Lube films do not need to be matter. Magnetic suspension in a vacuum
>does not have any lube film, nor does it have a wear issue.
>Electrostatic suspension in a vacuum is similar.

Forget your fantasy and get back to the task in hand - machine
ballscrews..

>As I said, the caveats are pretty severe, and the positioning system may
>be too compliant, but the backlash can be zero.

Try working in the aerospace or precision engineering industry for a
while then come back and tell us how it works in the real world.

>For a common, backlash free system used in real life, look at a speaker
>voice coil mechanism. It has no backlash, but it is far from rigid.

Again - BALLSCREWS - not speakers...

Steve Blackmore
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