Hi Craig

Don't get me wrong. I am sure ethercat works fine to control those motor drivers. And I am sure that those motor drivers can do what is claimed, both for motors and for sync and for accuracy. The big-name machine companies would not use them if they didn't.

It is just that those drivers are quite expensive compared to an ESS and a handful of Gecko drivers. And I am quite sure that when Mach(n) tells the ESS to tell the several Geckos to go to point x,y,a, that the machine will go to that point in full sync, to within one or two steps - and those steps can be sub-micron (0.8 um on my CNC). Whatever smarts the ethercat drivers have can be and has been reproduced in the ESS/Gecko combination. Both of these have powerful FPGAs in them.

The only limit I see at present for the ESS/Gecko combination (or UCC or others) is a power limit.
The stepper Geckos (G203V) I use are rated to 80 VDC/7A (1/2 kW).
The servo Geckos I use are rated to 80 VDC/20 A (1.6 kW).
If you need more than that you definitely out of my humble class!

Biased opinion follows. I rarely see any of my servos pulling more than 50 W. I rarely see the spindle pulling more than 300 W, and that is machining metal. The combination of a 3:1 gearing on the motor and a 5 mm ball screw gives huge forces. Granted, a commercial user may want to go much faster than I do. For that you need a LOT of cast iron.

Cheers
Roger