Re: Max feedrate of ball screws?

Hi Chris
I'm still building it but as soon as I get a nice overcast day I'll wheel it outside my shed and take a pic of it (my little camera doesnt handle bright sunny days very well). I use an endless chain over 14 tooth sprockets to reduce concentenary effects and the need to wrap the chain. The anchors to the carriage are fully adjustable for each chain to minimise squaring problems. I'm a woodworker and not real good at precision metal work so I made as much of the machine as adjustable as possible so I can compensate for my imprecise engineering hand skills.

Regards
Bob Thomas

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Chris L <datac@l...> wrote:
>
>
> echnidna wrote:
>
> >(snip)
> >
> >My machine will operate in your desired speed range. I have a counter shaft across the machine with a #25 pitch sprocket each end of my Y axis. The #42 Y axis stepper drives the shaft from the centre of the shaft to equalise torsional deflections of each end of the shaft. I feel for my purposes #25 pitch chain was the most practical method, it has a tenslie strength 860 -1000 pounds so I expect it will operate at 10 -15% of its strength.
> >
> Bob, Do you have a picture floating around ?? it be interesting to see
> what you have "cooking" with the chain drive setup. Especially curious
> how you let the chain approach each sprocket. Does it "Wrap" a little to
> get more teeth into the chain at one time ??
>
> I was thinking that this also makes adjustments for minor skewing really
> easy. If you have threaded adjustments on each end of the chain, you
> could simply adjust the machine to square. I suppose Plenty accurate for
> most large Router needs.
>
> You mentioned "upside down Rack:..... I once drew up a prototype Router
> with Rack and Pinion, where I kept the rack Vertical on each side so
> dirt fell thru it. Of course the pinion shafts were vertical, So, I ran
> them straight up, joined the pinion shafts from each side up top with a
> toothed belt. The Drive motor was in the middle of the gantry. It
> probably would work great with some of that fancy "cable" chain from
> Berg. Anyhow, it was only a drawing..... But I bet it would be smooth
> and quiet.
>
> Chris L