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

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.

4-4.5Nm is pretty strong for a stepper motor. You may have trouble finding a NEMA 23 motor that strong. And even then you are only talking about holding torque (their torque when not moving). The torque drops off quickly with speed.

I've heard good things about the closed loop steppers from Leadshine. Here is a 4Nm one, but it is NEMA 34.
www.ebay.com/itm/Leadshine-Hybrid-servo-...p2385738.m2548.l4275

The next refit I do of an old stepper machine, I will probably try to use some of those, but I have not used one yet.

You are right, i found only one 4nm stepper as nema23 (4wires) in the shop where i want to buy the ball screws etc.

...Now you gave me again the idea to use the closed loop steppers from leadshine... I checked the prices at aliexpress: 150€ per kit + delivery costs. (stepper + driver + wires). Wrote an mail to them and asked for the total costs include shipping for 4 kits, but i think it will cost me about 250 € more than i would pay for standard steppers + drivers drivers. Have to think about it, but somewhere i read that its an good combo to use closed loop/servos when using 2 motors per axis. Maybe i should go for it, but lets see how much the total price will be + duty costs.

Just worrying if the setup is more difficult.

4-5Nm is in that "grey-zone" where servos start to look better than steppers, but both can do the job.

Thanks tommylight. Good that you said that about the angular bearings, because i think i would order the wrong one..

I think 10m/min. is okay for me, but i am wondering if i reach 10m/min on the gantry axis (will be X i think) when using 2005 ball screw with direct drive.
Cutting at 10m/min is not really necessary for me, so i think there should be no problem when it comes to torque and when cutting at lower speed, i could make deeper cuts. Also like you are saying with the 05 screw i have more force so it will be totally fine ( i think )

@Todd Zuercher: When you are saying "servos", you mean real servos and not the the hybrid servos, right ? Because the hybrid servos are like steppers, but running quieter and have maybe couple more advantages + closed loop.

Guys, does it makes sense to go for closed loop hybrid stepper? I mean, will it make an big difference when using 2 motors for one axis ? I dont know anymore where i read it, but somewhere someone wrote its good to have servos or at least closed loop hybrid steppers when using 2 motors for one axis.

I believe the biggest advantage of the closed loop stepper is not having to worry about stalls or missed steps. But they also run cooler, can have more torque at speed, and like a servo reduce power or apply higher peak power as needed.

Thanks. How it works when using 2 motors for one axis. I mean what if only one side looses steps. Currently i cant imagine how it works, but somehow the the long axis (both motors) has to be synchronized in linuxcnc?

Im very interested to buy them even that setup would cost me 250-300€ more than standard stepper setup. Could be very helpful (gor an beginner) to not destroy every part until i know the best feed rates..

It is kind of obvious. If one motor misses steps, the axis racks, if it racks to the point of binding, both motors will likely stall.

A slaved motor gantry has problems with a servo system as well. The largest being tuning the servos initially. The potential for racking the gantry to the point of damaging it is quite high.

The ability to set up a slaved gantry relatively easily (without a number of creative workarounds) is only a recent addition to Linuxcnc, and is only supported in the development branch aka Master. There are a huge number of topics on this forum relating to this subject.