DIY Preload on a ballscrew
Greetings.
I'm the owner of some very cheap chinese C7 (so they say) rolled ballscrew. Diameter 20mm/pitch 5mm.
Obviously backlash is present and in a reasonable amount for the price but yet too big for my purpose. I was thinking about putting a double ballnut without replacing the screw but it is hard to find dealers that sell only the nut and also I'm not sure if I want to spend money on upgrading something that is not good in the first place (accuracy of the pitch isn't great too).
So I was wondering if it is possible to just replace manually the balls inside the nut and replace them with slightly bigger ones so to give preload to the screw.
Did someone ever tried to do this? Any suggestion on how much each ball bearing should be bigger (I have plenty of torque with the motors and I don't care too much about the life of the ballscrew)?
Thanks.
Re: DIY Preload on a ballscrew
Hi Stefano.
I am currently working on improving the chinese clone Hgr and ballscrews, and can tell their sizes vary quite a lot, so it is trial and error.
I just finished my hgr 20, and had to use 5/32" in -10 to -2um steps, and as there are 132 balls in each car it is a litle time consuming, but came out very well.
Now I am working on 1605 ballscrews, and plan to work up in sizes so 2005 will be next, but it takes a long time to get the right size balls, and they tend to be quite expensive in the g10 or g16 I buy, but still very cheap compared to the real ones, even hiwin.
Later I can make a thread showing how to reball and what sizes to use, but to answer your question, first measure all the balls in the screw find the biggest size and reload with a grade 10-16 of that size. if you still have play, go 2um (0.002mm) up in size, but be aware that more preload is more wear, so proceed with caution.
Good luck, Mike.
Re: DIY Preload on a ballscrew
Hi Mike,
Thanks for the answer. Hope to see your thread soon.
Good luck with your project.
Re: DIY Preload on a ballscrew
Mikeedd: can you post a link to the provider of the oversize balls you purchased? And if possible how you did the process?
Re: DIY Preload on a ballscrew
Quote:
Originally Posted by
Mikeedd
Hi Stefano.
I am currently working on improving the chinese clone Hgr and ballscrews, and can tell their sizes vary quite a lot, so it is trial and error.
I just finished my hgr 20, and had to use 5/32" in -10 to -2um steps, and as there are 132 balls in each car it is a litle time consuming, but came out very well.
Now I am working on 1605 ballscrews, and plan to work up in sizes so 2005 will be next, but it takes a long time to get the right size balls, and they tend to be quite expensive in the g10 or g16 I buy, but still very cheap compared to the real ones, even hiwin.
Later I can make a thread showing how to reball and what sizes to use, but to answer your question, first measure all the balls in the screw find the biggest size and reload with a grade 10-16 of that size. if you still have play, go 2um (0.002mm) up in size, but be aware that more preload is more wear, so proceed with caution.
Good luck, Mike.
I am also interested in your process and where you obtain the balls. I got some cheap HGR20 linear rails and found them to be very gritty. I removed the balls, cleaned them, cleaned the ball guides, reassembled, much better but very time consuming. My thought was to just discard the balls from the remaining carriages (there are a lot of them) and replace with brand new. But I could not find a source of balls. The balls seem to be a nonstandard size. Very close to 5/32" but not quite.
Re: DIY Preload on a ballscrew
Quote:
Originally Posted by
Mikeedd
Hi Stefano.
I am currently working on improving the chinese clone Hgr and ballscrews, and can tell their sizes vary quite a lot, so it is trial and error.
I just finished my hgr 20, and had to use 5/32" in -10 to -2um steps, and as there are 132 balls in each car it is a litle time consuming, but came out very well.
Now I am working on 1605 ballscrews, and plan to work up in sizes so 2005 will be next, but it takes a long time to get the right size balls, and they tend to be quite expensive in the g10 or g16 I buy, but still very cheap compared to the real ones, even hiwin.
Later I can make a thread showing how to reball and what sizes to use, but to answer your question, first measure all the balls in the screw find the biggest size and reload with a grade 10-16 of that size. if you still have play, go 2um (0.002mm) up in size, but be aware that more preload is more wear, so proceed with caution.
Good luck, Mike.
To reload a Ballscrew every other Ball has to be smaller or they will bind, so yes find the size that works and then use what is called a spacer ball between each ball the spacer balls are normally around .0002" to .0005" smaller, that is why when you take a Ballscrew apart you will find different size Balls, Quality Ballscrews and Linear Rails Bearings use a plastic cage between the balls to stop the ball to ball binding
Re: DIY Preload on a ballscrew
Quote:
Originally Posted by
mactec54
To reload a Ballscrew every other Ball has to be smaller or they will bind, so yes find the size that works and then use what is called a spacer ball between each ball the spacer balls are normally around .0002" to .0005" smaller
You stated that like a law of physics but is it? I have seen it contested. I'm not contesting it, and I don't have an opinion either way, just bringing up the fact that there are other opinions. I don't know enough to have an opinion.
Re: DIY Preload on a ballscrew
Quote:
Originally Posted by
strantor
You stated that like a law of physics but is it? I have seen it contested. I'm not contesting it, and I don't have an opinion either way, just bringing up the fact that there are other opinions. I don't know enough to have an opinion.
Then why did you post, this is how all manufactures make them, take a quality Ballscrew apart and you will find out for yourself NSK THK Bosch SKF Hiwin Etc
Of course you can reball your Ballscrew how ever you like your C7 Rolled screws are not going to notice how you reball them, they are still going to be a C7 low quality Ballscrew and sound like you assembled them with a bag of grit when you have finished
Re: DIY Preload on a ballscrew
Quote:
Originally Posted by
mactec54
Then why did you post, this is how all manufactures make them, take a quality Ballscrew apart and you will find out for yourself NSK THK Bosch SKF Hiwin Etc
Of course you can reball your Ballscrew how ever you like your C7 Rolled screws are not going to notice how you reball them, they are still going to be a C7 low quality Ballscrew and sound like you assembled them with a bag of grit when you have finished
I re-read my post it does not sound good. I came across badly. I apologize. I was trying to start a discussion about the physics behind using spacer balls vs not.
Months ago I took apart my NSK ground ballscrew/ Ballnut out of my CNC and at first I thought I had confirmed that they use two different sized balls. I was grouping them in two different cups. Soon I realized I needed a 3rd cup. Then a fourth. Depending on where I drew "the line" I may have needed 6 or 8 cups. I went back and started measuring the balls in the cups again, and got different measurements than I did the first time around. I realized that the balls were out of round.
I re-balled that nut using all same-sized balls, as I could not determine whether it originally had two sizes of balls, or what sizes they may have been. At that time I found conflicting information in forums about all-same-size vs spacer balls. I did not understand the argument for spacer balls but it seemed like the preferred method despite cutting the contact/thrust surface in half.
I have not had any issues from it, but I dont know how it will turn out in the long run. I have barely ran it. I don't know if I made a mistake or not and I'm apprehensive. I was hoping someone could explain better than what I've read so far. That is why I posted.
Again, my apologies for the way I worded it. I meant no offense.
Re: DIY Preload on a ballscrew
Quote:
Originally Posted by
strantor
I re-read my post it does not sound good. I came across badly. I apologize. I was trying to start a discussion about the physics behind using spacer balls vs not.
Months ago I took apart my NSK ground ballscrew/ Ballnut out of my CNC and at first I thought I had confirmed that they use two different sized balls. I was grouping them in two different cups. Soon I realized I needed a 3rd cup. Then a fourth. Depending on where I drew "the line" I may have needed 6 or 8 cups. I went back and started measuring the balls in the cups again, and got different measurements than I did the first time around. I realized that the balls were out of round.
I re-balled that nut using all same-sized balls, as I could not determine whether it originally had two sizes of balls, or what sizes they may have been. At that time I found conflicting information in forums about all-same-size vs spacer balls. I did not understand the argument for spacer balls but it seemed like the preferred method despite cutting the contact/thrust surface in half.
I have not had any issues from it, but I dont know how it will turn out in the long run. I have barely ran it. I don't know if I made a mistake or not and I'm apprehensive. I was hoping someone could explain better than what I've read so far. That is why I posted.
Again, my apologies for the way I worded it. I meant no offense.
If your Balls where that worn then the screw and nut would be worn also, in your case it would not matter too much, because of the amount of wear, normally the nut is measured and the screw if it is out of speck then it is reground for a new Ball size, what happens is the balls ride up on each other and this causes binding so if they have ( 1 ) smaller ball between each correct size then they don't get the binding the same
This is not always the case that you use a spacer Ball, high load Ballscrews have the same size Balls, ( they also wear much faster ) using spacer Balls cut the load rating of the Ballscrew but you have a lot less wear and almost no binding, ( has a much longer life if lubed correctly ) the posters where talking about C7 Rolled Ballscrews Not a C5 and above Ground Ballscrew which is most likely what your NSK Ballscrew was
