Problem Ballnuts Falling Apart


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    Default Ballnuts Falling Apart

    Has anyone else had a problem with the seals on their ballnuts coming loose? I've got 2510 screws on my X and Y and I have had the seals randomly come loose several times now. I can push them back into the ballnut housing but there seems to be an issue with the mechanism that's supposed to hold them in place. So far I've only been machining wood, but this still sucks that dust can get into the ball nut, and would be absolutely unacceptable if metal shavings were to get in there. I've been trying to get a hold of George, but haven't heard back. I'd like to know what's causing this, and if there's a solution to fix it as I can't keep running the machine when these seals are failing.

    Ballnuts Falling Apart-img_3233-jpg

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    Default Re: Ballnuts Falling Apart

    Not sure if they are the same as the chinese ones I have, but did you check the tiny set screws that hold the wiper in place?



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    Default Re: Ballnuts Falling Apart

    Quote Originally Posted by alan_3301 View Post
    Not sure if they are the same as the chinese ones I have, but did you check the tiny set screws that hold the wiper in place?
    They're made by TBI. I can't see any set screws, it looks like they're held in by a wavy wire c clip.



    If you look closely you can kind of see it in the pic.


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    Default Re: Ballnuts Falling Apart

    I have the same ballscrews, that wavy wire clip is shaped like a "c" when you pull it out. I'd start by pulling it out and giving it a slight bend. Compared to mine yours is barely visible.



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    Default Re: Ballnuts Falling Apart

    Quote Originally Posted by Andrew22 View Post
    They're made by TBI. I can't see any set screws, it looks like they're held in by a wavy wire c clip.



    If you look closely you can kind of see it in the pic.


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    Your screw look like they are lacking lubrication, this will cause extra friction on the seals and drag them out

    Mactec54


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    Default Re: Ballnuts Falling Apart

    Quote Originally Posted by mactec54 View Post
    Your screw look like they are lacking lubrication, this will cause extra friction on the seals and drag them out
    They've only got a few hours use on them right now, so I'd hope they could go at least that long without lubrication. I can still see a grease film on the screw, but you're observation makes a lot of sense as enough extra friction could be pulling the seals out.

    I'm trying to figure out if this is a case of the wrong seal design for a cnc router or a defective ball nut and what the best way to fix it would be.


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    Default Re: Ballnuts Falling Apart

    friction would have nothing to do with it. the seal will simply stay behind on the ball screw threads if not locked into place as the seal itself is threaded. if that wavy snap ring holds it in place, then you need to figure out how to get it back in. all of my ballscrews have end caps, or set screws. ive never seen the clip in seals so i dont know precisely how they are held. there might be instructions on the tbi website though.



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    Default Re: Ballnuts Falling Apart

    ok, so i cant tell what screw you have, but in their drawings/images, the ones with seals like that definitely use set screws to hold them in. i dont see any tbi screws that use anything resembling a spring.



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    Default Re: Ballnuts Falling Apart

    Quote Originally Posted by ihavenofish View Post
    ok, so i cant tell what screw you have, but in their drawings/images, the ones with seals like that definitely use set screws to hold them in. i dont see any tbi screws that use anything resembling a spring.
    I've got 2510 screws, not exactly sure what series but from the drawings on their website it looks like their SFU series. One major difference is the seal looks different. Unfortunately I can't get ahold of George to confirm exactly what he sent me. The seals on my ballscrew looks more like a square O ring than a proper seal with a thread profile molded in.


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    Default Re: Ballnuts Falling Apart

    well you wont be getting hold of george any time soon, so pop the nuts out of the housings and take some detailed pictures from all angles and post em. will help me identify how they work. a pic of one that has NOT fallen out would also be good.

    i just looked at one of my thk ground screws, and it does in fact have a snap ring on the seals, but its not like what i see in your pics.



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    Default Re: Ballnuts Falling Apart

    After taking things apart it's become obvious that the octagonal shaped spring clips would be more functional if they had a bit of a wave profile in them.


    I pulled out the rings and seals on the ball nuts to clean and grease them and it's surprisingly difficult to get the seals out even without any retaining ring (careful use of a dull dental pick worked best) which makes me wonder what exactly had enough force to pull these past the clips. The seals appear to have a slight gap that doesn't wipe dust from the very bottom of the thread profile. It would be nice to find a pre wiper to keep fine dust from sticking to the grease film in the bottom of the threads.


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    Default Re: Ballnuts Falling Apart

    So a quick update, after replacing and relubing the ball nuts a few times, one side of the y axis is holding the seal in a little better, but the other side it pops out after the machine has been running for a few minutes quite consistently. I sat watched the nut as I jogged the axis back and forth, and I feel like the cause is a combination of a flawed design and maybe a bad seal and clip, as the seal will start to spin with the ball screw (even with fresh grease applied) and screw itself out from the retaining ring. They're also running noisier than normal, likely because of some sawdust that I can't clean out of them which sucks.

    At this point the only solution I can think of is to replace the ball nuts, however I have no way of getting in touch with TBI to figure out if this can be claimed under warranty (if one exists) as George has all the order info and TBI won't respond to me.

    I'm not impressed at all right now, one of the selling points of Georges machines are ball screws on all axis which should be better than rack and pinion. Right now I'd take rack and pinion just to have a working machine if it were an option.



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    Default Re: Ballnuts Falling Apart

    odd. ive never had ballscrews like the ones in your pics. mine are quite different.

    but even still, the seals should not be unscrewing. i dont have any ideas at the moment though. you can try emailing george again. hes still in hospital, but is answering emails every so often (might take a day or 2 to respond).

    as for tbi, yeah, you wont get an answer from them. the screws dont come direct from tbi anyway, they either come via the chinese or US distributors.



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    Default Re: Ballnuts Falling Apart

    https://ae01.alicdn.com/kf/HTB1.O4UL...pg_640x640.jpg

    that looks like yours. see the little hols for the 2 set screws? im confused why yours would not have that.



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    Default Re: Ballnuts Falling Apart

    i cant find ANY ballscrew of that design, tbi, hiwin, chinese, counterfeits, without a set screw. somethings odd there. the set screw should "close" the snap ring and hold the seal in place. no set screw means not going to be held.



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    Default Re: Ballnuts Falling Apart

    Quote Originally Posted by ihavenofish View Post
    i cant find ANY ballscrew of that design, tbi, hiwin, chinese, counterfeits, without a set screw. somethings odd there. the set screw should "close" the snap ring and hold the seal in place. no set screw means not going to be held.
    It would be great if George were around to clear up this mystery. I've never seen a design like this before either, but George said they were better quality than Hiwin or other import screws and I assumed they would be decent. It could also be that TBI shipped the wrong type but it's hard to know for sure.


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    Default Re: Ballnuts Falling Apart

    So I was able to briefly get in touch with George, and he mentioned that these ball nuts are a new design from TBI that are supposed to be better sealed against dust. That may be the case if I could get this seal to stay in, but it's worse than useless when the seal pops out and there's nothing to keep the dust out. I even made a special lexan washer to fit between the seal and spring clip hoping that would add more support and keep the seal from spinning out, but that didn't work either. He was going to follow up with TBI about the defective ball nut, but I have yet to hear anything back, and who knows how long that will take.

    I also went to the trouble of taking off the entire ball screw from the machine to get a closer look and give it a good cleaning. I would have liked to have taken the ball nuts apart too for a really thorough cleaning, but the ball return covers are pressed in flush and I couldn't figure out how to remove them without causing damage. I've come across other covers that are plastic and can be gently pried out with a dental pick, but these caps seem to be metal so no luck there. Does anyone know how these caps are supposed to be removed?



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    Default Re: Ballnuts Falling Apart

    you dont remove the ball returns. you get a sleeve of plastic or cardboard the inner diam of the balls and roll the nut off. minor pain in the ass, but if you gotta remove em, thats the only practical way.

    seems like an annoying new design.



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