Slaving axis (rotating nut, 2 steppers for Y-axis)

Good, so i think i will use the rotating nut system and i will take the 2510.
The reason why i wanted to use the 2505 ball screws is, because i can only buy 2500mm long or 3000mm long ball screws, so my plan was to buy 2505 3000mm long and shorten both screws to about 2600-2700mm, so i could use one of the cutted pieces for the Z-axis (want to have about 20mm travel)
The travel only need to be about 2550mm x 1300mm, because the sheet metal plates and wood plates are mostly in 2500x1250mm. When i will buy the 2510, then i am not sure if i should use an 2510 ball screw (cutted piece from 3000mm long screw) for the z-axis, because i want direct driver the screw.
The other piece i could someday use for an other machine, thats why i also wanted to use the 2505 instead of 2510, but maybe i will just buy the 2510 and keep the total lenght and buy an 1605 ball screw for the z-axis.
Hope you understand me, and maybe you have some good solution for that.

To your question about the velocity: I think 10m/min would be fine, but currently i dont know hot to make the calculations when using ratios (not sure which ratio i should use for the rotating nut). The gantry ball screw i would like to direct drive, but i want to be honest, i have really no glue if that will work well, i mean rotating nut on long axis and direct drive for gantry. Also i dont know if 4 Nm - 4,5 Nm steppers are enough for all screws.

I think it would be a lot easier to use one motor for both screws, but i fear it will be too slow.

Just as a comparison
I have plenty of 2505, had one 2.4meters long mounted on a machine with direct drive from the nema 34 motor it could do 2m/minute before starting to vibrate, 3m/m was unusable. So i cobled together a rotating nut assemby with a nema 23 motor, it was wobly but moved so i pushed it to 16.8m/m. Could not push it further as one of the axial bearings was not seated properly so it was causing that woble. Still abot 8 times faster.
One detail i found in that test was: axial bearings are realy sensitive to the amount of preload, litle preload and it has to much baclash, more preload and it barely moves.

Thank you very much for the comparison. So, it sounds like rotating nut is the only way to go for that lenght. 16,8m/min is really fast, but i think 10-12 is totally fine for me. As long as i do not do it commercial its fast enough, but if i would do it commercialy, then i would for sure use servos. For now, its not necessary. What i am worrying about is the lubrication of the nut/screw.

My cousins husband works daily on manual milling and lathe machines with his father on their homeshop (gear production), and today (in about an hour) i want to show him some pictures and ask what he needs to make 2 pieces for me. I am just printing some pictures of Jonathans rotating ball nut (from mycncuk forum) and hope it will be not an problem to do that.

This is the rotating nut system from Jonathan (Post #74) : www.mycncuk.com/threads/3340-Rotating-Ba...t-design-ideas/page8
I want to build the exact same one.

One question i have:
You are saying that the axial bearing was not seated properly. Could you tell me how much bigger the hole has to be where the bearing will be seated in, so that it will fit properly ? The housing will be from aluminum and i dont know if the bearing needs to be "cold" pressed inside the housing or to first heat up the housing and then push it inside.


Thanks in advance.

Here is a good ball screw selection reference.
www.nookindustries.com/LinearLibraryItem/Crit_Speed_w_EZM_
(10m/min is outside of the acceptable range of even a 2510 screw at 2500mm length)
But if you rotate the nut instead both the 2505 and 2510 would be fine. (2505 up to 14m/min 2510 up to 28m/min)

To move at 10m/min with the 2505 screw you will have to rotate the nut at 2000RPM. A NEMA 23 step motor might be able to do that, but there won't be a lot of extra torque left. With the right drivers and power supply it should work though.

This is the rotating nut system from Jonathan (Post #74) : www.mycncuk.com/threads/3340-Rotating-Ba...t-design-ideas/page8 I want to build the exact same one.

If I am not mistaken Jonathan did have a few for sale either complete or in parts.

Todd, that was extremly helpful and thanks for the calculation. I should do it by my self, but i want be honest, even its very important to make some calculations while planning and buying parts, i want to go the easy way and look what others have build and copy it a little bit, because i just have too many things to think about. In future i will have more experience and can do some upgrades on the machine. I hope you guys understand it. I am already reading and planning since over 3 month, but this i want to start to weld the frame.

Good news for me are, that my cousins husband will make the 2 pieces for me. He said its not a problem, and he had also some small, but good ideas how to make it a little bit "better".

Now i am struggling if i should use the 2505 or 2010. The Ball screws i want to buy are from VTX (vertex precision - japanese company), but unfortunately i cant find any review about the ball screws, but the seller (famous shop here in Poland) said that they an very good alternative and i dont pay for the "make" like for the Hiwin ball screws/nuts. The price difference between the VTX 2505 and VTX 2510 for both 3000mm screws will be together only 50€, but the difference between 2510 VTX and 2510 HIWIN for both screws is about 250 €, just for 2 x 3000mm screws + nuts.
So i can invest the money in some good drivers - can you recommend me some for nema 23, 4 - 4,5Nm steppers? I am not sure if i should use digital (with stall detection) or analog drivers.

I think i decide later on which screw i take, but could someone recommend an good ratio for 2505 and 2510 for the rotating nut ?

@Clive S: Yes, that is true, but thank you for the info!
I am in contact with Jonathan (helpful guy). He made me an offer, and i really dont want say it was expensive, because his price was almost the half of the price from one german website, but i made some calculations and i will get it done much cheaper and no shipping costs from UK. Dont know the costs for the work right now, but because its my cousins husband who will do that for me, i dont believe that i will cost much and i will just bring him all the parts and some drawings.