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View Full Version : How to get the balls back in a ballnut?



Shinobiwan
20-12-2012, 03:17 AM
Don't laugh but a couple of months ago I had an accident that saw all the balls in a ballnut empty themselves all over the place!

Two things:

Is this even worth attempting a fix considering I've probably lost a ball bearing or two. (I might have them all but these things are so tiny I can't be sure)

If it is worth it then what the procedure for getting them back in? I can see a couple of plastic caps which presumably were used to fill the nut when manufactured but these push through rather than pop out so that rules out filling when the nut is on the screw. Only thing I can think of is drill a hole in the plastic caps and pop the balls back in then seal up with silicon or filler.

If all is lost can you suggest a decent (cheap) supplier of just a 1605 single ballnut? The ballscrew is virtually new so don't want to mess with that.

martin54
20-12-2012, 03:39 AM
try a search on the forum, pretty sure I read a thread on here about someone else doing that not so long ago & yes they managed to get them all back in so worth having a go.

Jan Rune
20-12-2012, 03:47 AM
Hi Shinobiwan,
Do you have one of those cheap 16-05 China ballscrews it is possible to reload the ballscrew. I have done it a few times to load oversize balls to reduce backlash.

Leave those plastic caps in place. If you turn the nut on the ballscew(either end) one revelution you can pull the outer nylon ring and stuff the balls in that way. I would have de-greased everything before i started and keep them away from anything magnetic/dust. I also find it easier to engage the nut a little when stuffing balls.

You might end up with a few leftover balls. But i havent found that to be a problem.
Jan Rune

Web Goblin
20-12-2012, 06:59 AM
Yes done that, balls everwhere.
Give the balls and nut a good clean before you start. Count the ball and seperate them into two equal amounts so that you get the same amount in each chain. Hoefully the ballnut has only two chains. What i used was a long pair of tweezers to replace the balls. I also stuck them in a little bit of grease to "glue" them in place when putting them back.
As Martin says there was a thread on this a while ago. A few of us have done it already.

Treemonkey
20-12-2012, 10:06 AM
I read a thread on here the other day, the guy said he put a magnet on the nut to help get the balls back in. Just have to make sure that your in a clean environment and de-magnetise afterwards.

Sam

Jonathan
20-12-2012, 10:35 AM
I've done this a couple of times...
Ideally you want a tube which is the pitch diameter of the ballnut minus the diameter of one ball, so if you imagine the nut fully populated it would just slide inside. You can then hopefully gradually slide the tube in, position the balls in the tracks with tweesers and grease to make them stick. With all the balls inside and the retaining tube, it will be the same as having a new nut, so you just push the tube up against the end of the screw and carefully twist the nut back onto the screw ensuring that the tube doesn't loose contact, else the balls may drop out. You can also try putting the balls in with the nut on the end of the screw and turning it as you go, that's worked for me once.

If you've got a strong magnet then stick it to the side of the ballnut, so when you put the balls in they will just stick to the nut. Ideally, I think you should demagnetise the nut afterwards. Obviously with any of these methods ensure everything is very clean before you start since swarf or just about anything except grease/oil in the nut will damage it over time, and it's sensible to do it in a tray as the balls are bound to fall out again!

On the plus side, it's a good opportunity to clean the ballnut! I've known ones I've got from chai to have small bits of metal floating around in them, which really doesn't help, especially when trying to get zero backlash by preloading...

motoxy
20-12-2012, 10:35 AM
I guess we have all done that! First make a cardboard tube, just roll up thin card, to go over the machining on the screw but will fit in the nut with the balls in. I used the magnets but found that thick grease held the balls in better. you will need a small screwdriver with a dab of grease on the end to place the balls inside the nut. When you have all the balls in place gently push in the tube. I rolled the tube up slightly smaller, pushed it in and let it expand. Then slide that sucker on. have fun.

Bruce

HA! jonathan beats me by seconds........

wilfy
20-12-2012, 02:05 PM
I guess we have all done that!


no not all of us.... i have no shame in learning from other peoples mistakes, i read the previous thread, and have told myself no matter how curious i am about the inner workings of a ball nut... i dont want my balls everywhere :P

motoxy
20-12-2012, 02:48 PM
Just wait, thats all i am saying, just wait

Shinobiwan
20-12-2012, 05:11 PM
Just wait, thats all i am saying, just wait

Haha! Oh yes!

Yep I'd been warned well in advance by Jazz that unscrewing the ballnut off was a big no no unless your a sadist.

So like yourself wilfy I wasn't curious enough to just wind the nut off and look inside. No, instead my accident was more spectacular. This was on the Z, I had no bed to limit Z travel and no floating end ballscrew mount to stop the nut either... cue me playing with motor tuning - a nippy 8m/min with slow slow acceleration. Wound it up to a good speed and then watched in horror as it slowed down like a snail all whilst smashing the Z 'up' button on the keyboard to no avail! Moments later, the Z axis front plate is off the machine and its raining ball bearings! lol Good times.

Humans... we are constantly finding new and inventive ways to f$%k up!

Ps. Thanks guys. I'll have a shot at this I think. Worse that can happen is I fail and go order a new nut.

Shinobiwan
20-12-2012, 10:28 PM
A new nut from Chai is only 16 including air mail. A lot cheaper than I thought it would be. Might just order a new one but will have a quick bash at getting them back in before that.

Robin Hewitt
20-12-2012, 11:37 PM
If you make a ball insertion tool it's easy :eagerness:

OTOH, making the tool is a right PITA.

Jonathan
21-12-2012, 12:23 AM
If you make a ball insertion tool it's easy

Could've told me that an hour ago, :wink::

771377147715771677177718

Actually it wasn't so bad with the big magnet, but if you don't have a suitable magnet then your way is a lot cheaper. It's a double start nut, so having 6 return tubes made it more difficult for the magnet to retain the balls, however they were sufficiently well held for me to be able to pour oil through the nut to clean it before putting back on the screw.

Earlier today I was removing the other nut from this ballscrew, holding it vertically and meanwhile the other nut decided to start spinning due to gravity and drop on the floor, so then I spent a while scrabbling around with the magnet finding the 51 balls. You can work out the number of balls per track, or at least get a reasonable idea, by simply measuring the pitch diameter and using that to find the circumference (accounting for the fact it's helical) and dividing by the measured diameter of one ball, i.e. ((pi*16.803)^2+10^2)^0.5/3.167 (https://www.google.co.uk/search?q=google&aq=0&oq=goo&aqs=chrome.1.60j0j57j0l2j60.2031&sugexp=chrome,mod=19&sourceid=chrome&ie=UTF-8#hl=en&safe=off&tbo=d&sclient=psy-ab&q=((pi*16.803)%5E2%2B10%5E2)%5E0.5%2F3.167&oq=((pi*16.803)%5E2%2B10%5E2)%5E0.5%2F3.167&gs_l=serp.3...7846.8113.8.8401.2.2.0.0.0.0.69.135. 2.2.0.les%3B..0.0...1c.1.C0vreD3jOUo&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.&bvm=bv.1355534169,d.d2k&fp=a5d91bad1ac8234a&bpcl=40096503&biw=1241&bih=606)=17 for this nut.

Shinowbian: I've got a spare RM1605 nut, so if you need one sooner than Chai can deliver then we can do a swap so long as you have all the balls.

Shinobiwan
21-12-2012, 06:54 AM
Managed to get them back in last night. Spent about an hour fumbling around with the first circuit of bearings then hit upon a trick and the remaining two circuits were done in about 10 minutes.

Only problem now is the ball nut feels a tad notchy at irregular intervals when turning. Its not binding tight just a moment of slight resistance then it free's up. At first I thought I'd gone and got a ball somewhere it shouldn't be so stripped it down again and took a more methodical approach. Cleaned everything again, separated the 48 bearings into 3 piles of 16 and carefully loaded them back in.

Still the same notchiness... hmm. This was a Strike CNC supplied ballnut/ballscrew and I can't say for sure if it wasn't like that before I spilled the bearings. Maybe I've knackered it up with playing around but I like to think Strike CNC, struck again!

EDIT: Seems to run smooth if you load the ballnut. Strange. Any thoughts?

Clive S
24-03-2013, 03:38 PM
I have just come across this Linearmotionbearings C7 Ballnut Flipping and Repacking - YouTube (http://www.youtube.com/watch?v=5qbVrRYzK5U&list=UUjoRKEpk7uE5Wzf4b-IFTFg&index=3) as it shows in the vid how to re fill ball nuts etc. Clive

John S
24-03-2013, 04:03 PM
That's assuming you have the same diameter at both ends of the screw.
If he'd just used a tube, no flanges and a couple of winds of tape round one end it then possible to use the same loading tube to switch to the same end. Just swap the 'safety' tape over.

Ricardoco
24-03-2013, 04:35 PM
Haha! Oh yes!

Yep I'd been warned well in advance by Jazz that unscrewing the ballnut off was a big no no unless your a sadist.

So like yourself wilfy I wasn't curious enough to just wind the nut off and look inside. No, instead my accident was more spectacular. This was on the Z, I had no bed to limit Z travel and no floating end ballscrew mount to stop the nut either... cue me playing with motor tuning - a nippy 8m/min with slow slow acceleration. Wound it up to a good speed and then watched in horror as it slowed down like a snail all whilst smashing the Z 'up' button on the keyboard to no avail! Moments later, the Z axis front plate is off the machine and its raining ball bearings! lol Good times.

Humans... we are constantly finding new and inventive ways to f$%k up!

Ps. Thanks guys. I'll have a shot at this I think. Worse that can happen is I fail and go order a new nut.

Ive read this three times and each time it gets funnier, I can only imagine the expression of desperation and shock on your face as you watch your Z front plate part company with the back plate, and the disbelief as the balls cascaded all over the place.... PERFECT!!

Rick