Re: Linear rail & ball screw size suggestions

Hi Ballendo,

I have been looking at plasma cutting machines in different shops to
get a feel for what works and what doesn't.

I spoke to a gentleman last week who purchased his 5'x9' machine for
$60K and said is paid back the investment in the first year.
less scrap, faster output and less manpower.

His linear shaft was open, which as I understand is a no-no on plasma
as it will get grit and wear. on the flip side is was located
outside of the mechanical envelope making it easy to access. This
means that if he has to replace $2K of shaft and bearings every year,
it is a small maintaince cost for his operation.

For us home shop guys, that would probalby equate to one replacemnt
every 5-10 years.

Dave

--- In CAD_CAM_EDM_DRO@y..., "ballendo" <ballendo@y...> wrote:
> Hello,
>
> A good question. Yes, it is an issue with these as well.
>
> One major difference however is that the seals on the linear round
> rails are pretty effective since there is no "open" area for
> dust/dirt to enter. And the fully supported open types have
effective
> wipers for the areas where the recirculating balls are rolling.
>
> The same cannot be said for a ballnut/screw assembly. Due to the
> rolling screw nature of the screw/nut interface, dust,dirt and
swarf
> will be "enticed" to enter the precision confines and wreak havoc...
> And the shape of the opening makes it difficult to use a wiper as
> above. "Brush" style wipers are often used, and will get the bigger
> stuff (Sealeze is one mfr.); but the only truly effective way to
keep
> the bad stuff out is complete enclosure, combined with positive
> pressure ventilation.
>
> Now let's get a bit back to reality<G> There are more than a few
> ballscrew/nut assemblies working quite well for many seasons which
> ignore many if not all of these suggestions/rules... Just know that
> the farther you get from the suggestions, the greater your chances
of
> early failure, or poor results.
>
> In the meantime keep in mind that the people who make this stuff
are
> trying to be sure that the choices made by a customer do not shine
> badly on their product, and are often dealing with designers/
> engineers who for ecomomic reasons are forced to push the
envelope...
>
> Hope this helps,
>
> Ballendo
>
>
> --- In CAD_CAM_EDM_DRO@y..., "J.Critchfield" <js3mc@a...> wrote:
> > If dust is an issue with ballscrews what about ball bearing linear
> > components?