Alternative to recirculating ballscrews.

[NeoTech]

These uses a "normal" pitched thread instead of a acme thread. And makes use of smaller rollers that mates with the main axle thread.
They are driven by small gears on the ends of the rollers and indexes by that means. Im guessing the gearing ratio must be similar to a planetary calculation for correct turning of the rollers against the thread on the leadscrew.. Anyways..These are actually manageable to make on your own rather than the ballscrews that is a damn hassle (have tried).
See video below.

EDIT:
And well i found an old clip in my saved files that i think will add to this little idea nicely; this is the homemade version i guess. =)
[ Invalid YouTube link ]

[awemawson]

Nothing showing for me in the pictures - just a blank space

[andyf]

The videos show up fine for me.

Andy

[AdeV]

Is it actually a non-backlash system, or just a way of gearing down a leadscrew?

Andrew - the "pictures" are youtube links, codes oMd7Lqian48 and iPkoGug-oC0 for top & bottom ones respectively.

[NeoTech]

Its actually a linear leadscrew, its a replacement for ballscrews according to SKFs homepage. It can do both finer resolutions and more coarse resolution then an ordinary acme screw. And it can do it on a normal metric pitch thread..

[awemawson]

Is it actually a non-backlash system, or just a way of gearing down a leadscrew?

Andrew - the "pictures" are youtube links, codes oMd7Lqian48 and iPkoGug-oC0 for top & bottom ones respectively.

Yes I appreciate that - I was just getting a lined box with no active areas, but strangely now they show normally. How odd as nothing has changed on my pc.

[BillTodd]

There's a very very long thread about these on cnczone:

http://www.cnczone.com/forums/linear_rotary_motion/13593-different_better_kind_screw.html

(including my own small contribution as fitted to my drill/mill ):

[NeoTech]

Billtodd, extremly cool to see someone actually made one.. Even if its a different design.. But very cool, i will do an attempt at creating on as well but with that planetary design i need a smaller nut.. =)

[John Stevenson]

That's the problem with these alternative designs - the nuts are always bigger.

Also whilst it's cool to make it yourself you are limited to using soft components so the subsequent wear will soon out weigh any cost saving if there were any in the first place.

John S.

[NeoTech]

Oh, i have aquired an induction furnace a while back, controlled hardening isnt a big issue. Its more a question of getting the fuse to hold for the furnace ;D

I will prob. try to make the roller out of toolsteel and harden them if i try this.. first attempt will prob be bronze though. But yeah, size is a problem. Although Bill's solution is neat and works well for a saddle on a medium sized bench machine i dont think i would be able to fit a solution like that on my BF20 mini mill.. But i have a winter of car building standstill experiments shall be made. =)