[natural]

Hi All, Been a lurker for a long time, but this is my first post. Long story short... I need a pair of long ACME screws (like 9 feet) w/ antibacklash nuts. I was wondering if anyone knew a good source... finding the screws doesn't appear to be a big problem. I know Roton. My biggest hangup has been antibacklash nuts in larger sizes... 1/2-10 seems to be the most common, but I'd like something in the 1" range.

If anyone has any insight, I'd much appreciate it. I've searched and searched but maybe I'm just using the wrong terminology. Thank in advance!

[OCNC]

If anyone has any insight, I'd much appreciate it.

Acme Anti-backlash nuts to 1" dia.

[RicknBeachcrest]

Here is a popular site for ABN's

dumpsterCNC - anti-backlash solutions for home and industrial linear motion

[ger21]

You can get 7/8" or 15/16" screws and nuts here. NTB Anti-backlash Nut - Kerk Acme Lead Screw Assembly

You'd probably be better off with 25mm chinese ballscrews, if the shipping isn't prohibitive.

I have a feeling that the screws in the link I posted are not going to be cheap.

[Devastator]

Acme Anti-backlash nuts to 1" dia.

Gotta love that 25% efficiency rating in the larger sizes. For that length, fixed ballscrews with a rotating ballnut might work really well.

[louieatienza]

Lead Screws - Main Page for Acme Screws and Nuts - Roton Products

[natural]

Thanks for all the responses. Looks like a 1"-5 might be my best option based on what ive seen here. Though a 0.2" lead isn't ideal especially for this length of screw. I'd love to use a couple rotating ballnut screws from thk but I don't think that's in the cards for me.

Regarding Chinese ball screws, do you you have a good source?

Thanks again everyone, the help is much appreciated.

[ger21]

You might want to consider these screws, and possibly make some nuts like these
They'd be far more efficient. 1" acme is only about 30-35% efficient, and isn't really a good choice for a big router.

[ger21]

Actually, if you decide to make your own nut, these would be much cheaper and have the same efficiency as the ones I linked to above. 1 X 1.000 Right Hand Hi-Lead Lead Screws & Nuts for Power Transmission - Roton Products, Inc.

[natural]

Hmmm definitely giving me some stuff to think about. I saw that thread about making your own nuts... tempting.

What about something like this with mating ballscrews? Thoughts?

1 X 1.000 Right Hand Recirculating Lead Screws & Nuts for Power Transmission - Roton Products, Inc.

[ger21]

A much more efficient option than the acme. However, I've heard that you'll probably need to repack the nut with larger balls to get rid of backlash.
They're also probably not the most precise ballscrews, but I don't see them being any worse than the acme.

[ger21]

Have you considered rack and pinion? The systems from cnc router parts would probably be a bit cheaper, since the two screws alone with no nuts or mounting hardware will be $500 to $700

[natural]

I have looked into R&P, and have decided I'd rather stick with screws for a variety of reasons. Maybe, I'll end up there in the end, who knows.

But for now, how much backlash are we talking with Roton ballscrews/nuts? I read that Roton claims a 0.006" backlash in this thread: http://www.cnczone.com/forums/diy-cn..._backlash.html
Is the ball replacement something that Roton offers? Perhaps I need to give them a call. I've also heard their lead accuracy isn't fantastic, anyone have experience there?

Thanks for all the help thus far!

[ger21]

All I know is what I've read. I believe you'd need to reload them yourself. I think you also may need to get the ends machined yourself, but I'm not positive on that.

[louieatienza]

What a few folks in the metalworking forums have done with Roton screws is use two nuts per screw, and preload them against each other with a spring of some sort, like wave washers. You can only preload the screws to a point; part of the reason there is "backlash" or clearance in the ballnut is to prevent binding in case there are deviations in the pitch. Preloading one nut against another with a spring can "take up" any slack; the spring "tension" should be at least as much as the required force to move the axis...

And yes, unless you're an OEM needing hundreds of screws, Roton does not do end machining.

[natural]

Thanks for the responses guys. I'll probably talk to Roton at this point and see what their real backlash numbers are. 0.006" doesn't worry me a ton, but I'll probably do it right once if their numbers arent better than that.

Seems the anti-backlash acme nuts I've got here use a torsion spring... is that more common or something like a wave washer? Force required to move the axis including a ballpark cutting force I assume?

Thanks again, leaning towards those ballscrews at this point

[natural]

From the horse's mouth:

Roton ballscrews seen here: 1 X 1.000 Right Hand Recirculating Lead Screws & Nuts for Power Transmission - Roton Products, Inc.

Backlash with mating ballnut: 0.004"
Lead accuracy: 0.003"-0.006" per ft
Efficiency: 82%

Also they do offer to swap out the standard ball bearings with slightly larger balls for $20 per nut. That can reduce backlash to 0.002" but they obviously don't recommend it.

[kevincnc]

I have some unused double nuts (you can preload them for zero backlash) for 1" diameter, 1" lead Rockford Ballscrews.

Search Results - Rockford Ball Screw

Not sure if they'd work with the Roton screws, but Rockford used to have pretty good prices. Let me know if you're interested.

[arizonavideo]

If you can stand .006" of backlash then you might look at a chain drive for the long axes.

Reallly cheep and efficent.

The 5/8" Rotons ball screw's can get down to .002" easy with larger balls. Most of the time its .127"

A rotating nut will let you run a smaller screw so you could go with the 5/8" and be fine.