Re: [CAD_CAM_EDM_DRO] Was: Linear rail, accuracy in general

Hello friends,
I see you worry much about straightness because of temperature and
machine stability..
There is an effect that is several thousand times more critical.
Liberation of stress!!!
Just make a test with any material.
I had to make some back ups to clamp knife blades in a wood planer a few
weeks ago.
3/4" 1020 steel of 25" (63 cm) length had to be milled down to 1/2". As
soon you unclamped the piece it came up like a truck spring with a gap
of 3/8" (9 mm) in the centre. 15 hours hole project plus 4 hours bending
it straight!
Everything is relative. You best determine first what the real
requirements are. And as showed here there might be effects that wipe
out all your neat preparations in a second.
(exp.: loose gib or lead screw nut)
Have a nice weekend.
Sven Peter

"John H." wrote:

>
> > On large workpieces, and large machines where the point where the nut
> drives
> > the axis is far from the actual location of the part, these expansions
> reach
> > levels of hundredths or even tenths of inches very easily. Workpiece
> > heating and tool and spindle expansion is even more a problem that
> > table and leadscrew heating, so these are the first places to look for
> trouble.
>
> Why aren't the machines put into some sort of water tight bath and just
> submerged in coolant while they're working? The rapids and high speed
> cutting wouldn't be as fast but the surrounding coolant would suck up heat
> much faster than air can. It could also be pumped through and kept at a much
> more constant temperature than air (A high latent heat capacity I think
> that's called).
>
> Does coolant, being a high percentage of water, not rust machinery because
> the parts it contacts are usually stainless or chromed? The tooling business
> with the machines if real cleaver, I like it very much so! : )
>
> John H.
>
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