70mm Level Winding Device utilizing Diamond Ball Screw (includes CAD links)

by JawzX Mar 22, 2019
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another question: what the purpose for the holes in the inner ring?

The holes in the inner ring are for the 4.5mm BBs that follow the track. see attached image:

I printed one, but it's not work well. can you put any video for how to improve this?

To prevent short-stroking, have the "guide pin" not be BB, but make it have a flat that is long enough to bridge the intersections of the curves (and give a a rounded front so it won't snag).

Ah, yes I can see how that would work. I think it would work best with a narrower guide thread, then direction changes at the ends could still happen without binding. I found that the latching BBs method used in the "experimental latching inner nut" works quite well, and still confers the advantages of a ball screw design as it pertains to smoothness of operation.

Is it possible to redesign the outer ring where you have the alignment travel pin and the eyelet the martial is thin if you scale it down and it rips open when you place it over top the first ring.

see my reply to your earlier question... just thickening the outer nut should largely address your problem, but these parts were not really designed to be printed any smaller than they are. a clean-sheet re-design (by all means, use what you learned from this design) intended to print smaller or for smaller travel may be more fruitful than scaling this.

Can you Mod the parts that have small pins for holes so i could inset metal pins to make it easier to print and scale please ? Not the main roller just the other parts,

I may eventually get around to these requests, but I am quite busy with the rest of the project that uses this... I'll add the CAD files to the Thing and you can attack it yourself. I made this the size it was as a sort of minimum scale that I thought was practical to print with a .4mm nozzle on an FDM machine. (though I see in your profile that you have a DLP and LCD resin printer....) If you need it smaller I might suggest starting from scratch with a similar diameter screw and ball diameter, but a finer pitch thread to cover a smaller traveled area. (hint: use the spiral tool in your CAD tool of choice to create the ball track)

check these public Fusion 360 links:

main screw: https://a360.co/2Oxupo8

frame: https://a360.co/2OATcrr

thanks for sharing the files, ill post a remake crediting your work.

I look forward to seeing your modifications. It really surprised me that I seem to be first one to post a functional self-reversing screw (other than a novelty "bi-directional nut" toy) on thingiverse...

There was Russ from Rwgresearch that made one, but was lot bigger then yours, and not well suited for scaling ,and you right, its odd that there not pages worth of them, they could be very useful for many applications. perhaps the geometry for the travel path is more tricky then it look ?

the only thing I did to the screw after cutting the two counter-rotating spirals out of it was round the end joins a little so the direction transition wasn't so sharp. As you work on yours, you might consider smoothing that transition even more to avoid binding at the direction change, but mine works quite as is. Once I realized the latching (detent) leader/follower bearing track in the inner nut it worked 100% with no false-reverses.