Nema 34 on Ballscrew Systhem

I need help on this one,

I have a cnc with rack and pignon and I will like to change for a ballscrew systhem
Can i use my step motor nema 34, 650 oZ with ballscrew 16 mm with out reducer for X and Y axes?

My machine will be home made 24 x 36 inches bed mounted with 20mm Hiwin linear guide rail, mounted on T slotted aluminium profile (3030).
I am planning to put my 3 Nema 34/640oz/4.2amps/1.8deg. with killing driver 5.6amps/50 vdc on each side of the bed and 1 on the gantry,
1 Nema 23/255oz/2.8amps/1.8deg. for the Z with killing driver 4.2amps/50vdc.
All this will be mounted directly on 16mm ballscrew (double ballnut) one star 5 turns by inch .2 pitch.
The power is 2 power supplies, 36vdc/10amps and my step motors are connected in parallel.
Regarding the moving weight, I have a T slot aluminium bar 3'x6' with a Bush router(planning to have a 2.2kw air cooling router later).
I am cutting wood, plastic and occasionnaly aluminium. I will need to run the machine around 50 to 200 inch/minute.
I will appreciate your help. Thank you in advance.

You can certainly run those motors direct drive on the ballscrews, but at 36V I doubt that you will get 200 IPM reliably if you are using 1605 ballscrews. The linear rails will help having very low drag, but with 1605 ballscrews the RPM needed for 200 IPM is 1020 rpm. That is at the upper limit of what just about any open loop stepper can handle from my experience. Add to this that a 640 oz-in 4.2A motor is going to be around 7mH inductance and would ideally need about 80V. At 36V your torque will fall off faster. I would definitely boost the voltage to the max your drivers can handle (48V). If you were to use 1610 ballscrews then you would only need 1/2 the rpm and things get more tolerable.

Now I am considering a total new plan and will be going with 4 new Nema 23 on my 1605 ballscrew.
Do you think that Nema 23, 425 oz 9.7amps will be powerful enough to run at least 120 IPM?

Thank you again for your help.

Why on earth would you couple these beasts of steppers with so flimsy ballscrews?

Because at first I wanted to use the Nema 34 that I already have on my old 4'X 4' rack and pignion cnc (which is to large for my garage), but now I may just sell it and built a new 2' x 3' with the Ballscrew that I bought not long ago. So now I thing that I am better to go with 4 new step motors Nema 23. However, I am not sure of the size. Can you provide input to help me achieve this. It may not be the best solution, if you have a better idea please feel free to let me know.
Your input is very much appreciated.

Hiya Paul, I don't understand why you want to cut at that feed rate. I have 16 mm screws with 5 mm pitch and 465 oz/inch mema 23's and max speed that I use is 1600mm per minute (about 320 rpm) and can cut ally 1mm DOC. Any faster and the motors stall, however the expensive Gecko drivers can give you more speed but are out of my price range here in Oz. Ball screws get lots of whip when getting close to 1000 rpm but you would need servo's to get that speed if driven direct. Also at close to stall speed for the motors they won't have much torque to cut anyway.

If you really want that speed with enough power in your motors to cut something you will need to either gear up the screws or buy screws with a much higher pitch at least double perhaps, then nema 23's may be too light on. I have tried with 1600 inch/ounce nema 34's, 60VDC and 6 amps geared 3:1 but at 850 rpm on the screws they start to vibrate and I never tried to go faster incase I broke something.

To get those sort of speeds you really need to use a rack on the X and Y with nema 34's, like you have now.

Good luck with the build.