[Corvus corax]

I have been spending literally all my disposable income (and some not so disposable) on parts for my machine, mostly off of Ebay. So far, aside form my mistakes, I've been getting along well. But today, one of the most expensive purchases I've made thusfar arrived on my doorstep, and was eagerly unpacked: My 48 inch travel ballscrew. Precision ground, C3, 1.25 inch diameter, the works. I paid almost $400 for it. It arrived in a PVC TUBE! The ball nut was used to support the assembly in the tube, and it must have taken some HUGE falls, because the nut is nearly frozen solid on the shaft. The worst part is, I paid a premium to get a screw that was NOS.

The balls appear to have been flatspotted, the nut will only move with a crunchy motion in one direction down the shaft. Try to go the other way, and the nuts locks like a ratchet. I rolled the wipers down the shaft a bit to see of something got into the nut, but it is clean. I flushed the assembly some with light oil, and nothing came out. There is some rotational play before the ballnut even engages, and though I cannot see any damage to the shaft, I'm sure the whole thing is FUBAR. I am absolutely devastated. I had a chance to buy many other screws which were even better than this one, but I passed them over. Now I have to find another screw just like this one- the machine is already coming together, and parts have been cut. I am absolutely screwed. :drowning:

[JavaDog]

Not to be obvious, but please tell me you paid for shipping insurance?

[Corvus corax]

I'm pretty sure I did- but improper packaging is NOT covered. Its up to the seller to make this one right. I've dealt with UPS before on things like this, and the packaging was laughable, they REQUIRE 2 inches of crush zone around all shipments, regardless of size, and the ballnut was actually visible on the outside of the package when I received it. I could see where they taped the thing up after bashing the hell out of it. There was no padding in the package. I'm going to check, but I don't even think the ballnut will fit inside the tube- the top portion of the tube was broken or sawed in half to allow the assembly to fit inside, the ballnut run to almost the end of its travel to allow it to fit. I haven't heard back from the seller yet. I'm hoping they have another to replace this one, though I am dubious. :bat:

Is it possible that the screw, since its new, is simply "tight"? I cannot find any damage on the shaft...

[HuFlungDung]

I would get a large cookie sheet out, and remove the ball return tubes, and gently work the nut back and forth, letting the balls drop out slowly into the pan. Or, if you can run the ballnut right off the end, then do it.

It could be that some of the balls are caught in between the ball return tubes, due to improper assembly, and this could cause it to lock up. I really doubt that typical handling would have damaged the ballscrew into this non-rotating state that you describe, but I would imagine it would be bent if mishandled to the degree you described.

[Corvus corax]

I was thinking something along those lines- but... How do I get the balls back in? Also, I think I may have located the problem. In scanning the surface of the ballscrew carefully, I found spots of RUST! I'll bet the balls were funky before this thing even saw the shipping tube. There are no external ball return tubes for me to remove, unfortunately. Any ideas?

[cbass]

I really hope for your sake that it is fine.

If on the other hand it has been damaged, I can't help but think the seller/shipper is responsible, regardless of wether you paid for shipping insurance or not. The shipping company can not be faulted for something that is not properly packaged.

There's no point in shipping a 48" long, precision ground ball screw without proper cushioning and support along the entire legth of the rail (unlike support only in the middle, as you described). With that much unsupported weight, I would expect a bent shaft when it arrives to its destination.

If the issue with your unit ends up being due to shipping damage, I would take it up with the seller, assuming insurance will not cover it. If you get no satisfaction, go to ebay directly.

Good luck

Carlo

PS Come to think of it, I think ebay does cover improper packaging. You'll need to check.

[wisp]

Hiya Corvus, you say the ballscrew is 1.25" diameter? i SERIOUSLY doubt it was bent during shipping. You can not bend a 1.25" dia. ball screw to the point the ballnut sticks just by dropping it.

You really have no choice but to remove the balls from the nut. At the very least, remove one of the tubes, and examine the balls for rust, you can easily replace the tube with the balls in it. You really have to find out if the balls are rusty. If they are, just buy some more, they are not too expensive.

If the balls do not appear to be rusty, then clean the rust from the screw as best you can, and then REALLY grease the nut up, until it squirts out the seals. A lack of lubrication in the nut can cause the balls to slide rather than roll. If you plan to use an auto/manual oiler on the nut, then connect it to your oiler and run plenty of oil through it.

The balls could also be sticking in the tubes, another good reason to take them off to see if the balls roll easily through the tubes.

Best of luck.

[HuFlungDung]

Rust in the balls, nut or screw would explain a lot. I'd sure try to get my money back. There's nothing you can do to repair the pitting.

I've never handled a ballnut with internal ball return, so i'm not sure how they are assembled. Perhaps they load all the balls in with grease to hold them, then slide a close fitting dummy cylinder inside so none can fall out, then butt the end of the screw up against the end of the dummy, and screw it on through....very, very carefully.

[Corvus corax]

Here's a theory: The seller wanted to pack the ballscrew up, accidently ran the damn thing off the end of the shaft, picked the balls up off the floor, and just barely managed to get it back on in order to ship it. I still haven't got the ballnut off yet, but I'm VERY slowly trying to run it up to the end, as it only wants to go one way, and THAT end of the screw is where the threads end! I can get it to move backwards by jiggling, swearing, and getting about a 1/16 rotation out of it each time. I moved the stupid nut down the shaft the other way while fiddling with it earlier, by about 8 inches. This is a 1in 6 screw, so its going to take a while! The rust is very superficial, and is just a couple of small spots in the bottom of the track in the middle of the screw- no where near this area. I'll remove them carefully if I can get this thing sorted out. Otherwise, its going back! I've assembled plenty of engines before, so keeping little bearings held in place with grease is more of hobby than a task!

[HuFlungDung]

If you do get it apart, you should check all the balls by measuring their diameter. You need to adopt a micrometer technique that will allow you to measure consistently to one or two ten thousandths. Set up a series of bowls or something to sort them into different diameter classes. Either they should all be the same (within a tenth), or there should be two different size classes. If you find the latter, then reload with small ball, big ball in sequence.

If you find a few balls with a significant discrepancy from the norm (too large), set them aside and do not use them, as they could be the trouble makers.

[JFettig]

I suggest that you leave it as is untill you hear back from the seller. Some people would be stupid and that now that you took it apart, they wont take it back.

give it a couple days if needed.


Jon

[Corvus corax]

I've got the nut back in the same position where it started, and it looks as if its going to stay there. Pieces of broken bearings have begun dropping from the nut, and I'm dead sure the innards are lacerated. Its a paper weight. I was right the first time. The shock of being dropped in shipping crushed the bearings into sharp shards, which then had their way with both the screw, the intact bearings, and the insides of the nut. I'm going to leave it for now- I wish I could fix it, but it looks as if its a lost cause. All because someone was too lazy to pack the assembly properly!!!

[JFettig]

how hard have you tried to contact this guy or ebay to get this straitened out?


Jon

[2muchstuff]

The amount of force to break a hardened ball is tremendous, the. To do so in shipping would result in a majorly destroyed box, the PVC would be shattered. I would almost bet it was shipped that way.

[Corvus corax]

J fettig: I just received the item this evening. I have sent two contact emails through Ebay to the seller, but I was hoping it was something I could solve myself. Alas, it is not. I'll wait a day or two for a reply, then I'll email them directly, and/or call. I couldn't beleive it when the pieces of balls began dropping out, I just about crapped myself. I doubt the shaft was this way before being shipped- someone would have had to really try to break those balls. They are quite small, less than 1/8 inch in diameter, so I can see them being broken if the screw was dropped hard enough.

[cbass]

Was the item described as "like new", "perfect condition", "fully functional" etc. In other words, did the seller lead you to believe that this unit was in working condition? Ok, this is a bit of a rehtorical question. My point being that for $400, you should be getting something that WORKS. If, on the other hand, the buyer described the product "as is", well thats a whole different story.

Assuming the product was described as being in working order, I think its safe to say the description of the item was misleading. I know ebay protects buyers in cases like this. I'm just not sure if there is a minimum value required for the product before this sort of protection kicks in.

[Bluesman]

I spent 10 years in the Acuator bis, Certifide for inspection and final assembly, I can tell you without a doubt that the ballscrew was not damaged in shipping. They are hard steel balls and the Ball ride in the nut and the screw is also hardend.
Now if you are lucky you may just need to reball the assembly. You can dissasemble the entire untit and check the ballride for scalling in the screw and the nut. (Make sure it is nice and smooth) If it is just rust that is easily fixed just stick the screw on a lathe and run some scotch bright in the threads groove using a 1/8 dia cord to pull the scotch birught into the thread.(WD-40 for lube)
Mic the balls and make sure they are all the same size some repiar houses use difrent sise balls to take up lash and still let the nut move.
It sounds like the nut has internal crossovers which is acually easier to rebuild that the external. Just run the nut all the way of the screw and let all the balls fall out. Check them to see what size you need to replace them. (you can order new ones from Tompson ball)
Then after you polish the screw and the nut you put the nut on the screw so that the crossover is past the shoulder of the screw and begin to fill with the new balls. Once it is fill run the nut the rest of the way on and it will keep the balls in place.
Now if you would rather not mess with it then call EJM ballsrew in Bay City MI. They are the best around at repair and will do an honest job. If they can just clean it and reball it they will. And they will give you a free quote on the repair and if it is not repaiable tey will tell you. You can overnight the screw to them and they will turn it around quickly
Call EJM @ 989-893-7674 if they cant fix it they may have an inexspensive one they can replace it with. Normally the cost to rebuild is about a 3rd of a new one.

Bluesman

[Corvus corax]

Okay! got the nut off after 5 hours of work- working it back and forth on the screw until I go to the end. just found out how sharp the lead in grooves are inside of ne of these, split my index finger knuckle wide open! I am bleeding on the keyboard as I type this. All the way across- yeah... Nice. :tired:

Anyways- I have found the remains of about 20-30 balls, crushed to very sharp splinters, and most all of them were lodged into the inside portion of the nut. The tracks appear to have escaped damage, though the pieces of balls dug into the end of the ballscrew as the nut was being removed, which makes the future of the last 4 inches or so uncertain. I suppose it could be machined off, or simply ignored as it is past the end of my intended travel. Now, I have about 30 balls or so left, and I'm thinking about getting hold of the manufacturer to get some more.

I don't really find this a satisfactory purchase, though I went back and chacked, and with shipping I paid about $250 for the whole thing. It was sold as new, by the way. And I can guarantee the damage was done in shipping, because the photographs in the auction clearly show the nut in the center of the screw. There is no way the seller would have gone through what I just did to move the nut for shipping! So Bluesman, I believe I have just presented you with the worlds first case of balls being busted by the UPS man! :rainfro:

[ynneb]

And I can guarantee the damage was done in shipping, because the photographs in the auction clearly show the nut in the center of the screw

That means nothing. How do you know the one in the picture is the same? Maybe the seller was palming you off a dud one. For the matter, its only a matter of moments to doctor a picture.

A few here have suggested it could not be damage in transit, I fully agree. For starters the screw would be bent b4 the balls were destroyed from such a force.

Stop playing around with it and demand your money back. Its that simple.

[DennisCNC]

Don't loose hope! Most people on eBay will work with you on a situation like that. Atleast with me in the last ~7 years.

To damage a 1.25 screw you need to a big truck over it.