Controlling 6 stepper motors and 2 spindles on a budget

[JAZZCNC]

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I need to perform FSW and ISF double sided.
So for FSW, the tool will go down towards the work piece then across as it is welding. ISF tool will go towards workpiece on both sides then machine a truncated cone similar to the ones in the julian allwood papers, I hope that helps explain my g code issue

Ok know I get it.!! Very Ambitious with no CNC experience. . . . Hope you have built it strong.?

To be honest I think your going to struggle on few fronts. Budget Firstly but also on Spec and what your trying to achieve from the motors/drives.

You'll never run nema 34 motor with Arduino drive and get any usable speed/torque from them, if can do it at all.? Nema 34 motors require much higher current than most Arduino drives will probably offer but more importantly you'll need high voltage to have any speed and Torque. Again very much doubt Arduino drive will allow much above 50Vdc.
To get 1000Rpm with any torque left from nema34 will require much more than 50Vdc. Much after 900rpm Torque starts dropping quickly with larger motors. So if you want high speeds and torque you need high voltage. Often this means using Mains voltage drives which are expensive.

Similair story with the Nema23 motor and Gearbox. If ratio is anything above 2:1 then you'll never get 1000rpm on the output shaft from stepper motor. Most Nema 23 motors even when run with good amount of volts (60-70V) will struggle to reach 2000rpm and have any usable torque left.
Again to get good speed and Torque you'll need more volts than Arduno drives will allow I think.? . . . . . I'm not into Arduino's but this is industrial strength stuff your getting into and IMO Arduino's are not going to cut it.!

Be careful because your Budget will be gone in blink of eye.!!! . . . . It's most Common mistake in CNC trying to cut corners by doing it on the cheap with toy setup's only to realise after all the money is spent that got it wrong.