My #TravelCNC didn’t want to go past 2000mm/min.
Just updated #MACH3 kernel speed to 100KHz and set the motor max speed to 4000mm/min (not touching the acceleration).
The Xulifeng controller card can do 200KHz and the stepper drivers are running at a fraction of their rated load anyway.
Z axis is a bit choppy now at 3000mmm/s doing wood with Z-0.5mm .
3900mm/min now.
The Z axis is the only axis that uses one of the old stepper drivers.
So I guess it will stop being choppy with one of the 5A drivers, when the voltage is no longer above it’s absolute maximum rating. 
That’s cooking. Mine’s limited to about 1500mm/min thus far.
At these speeds I noticed that acceleration is the limiting factor.
…and tollerable audio levels.
Surprised that isn’t loud as hell.
Normally it’s not louder then a sewing machine.
I guess with a better stepper driver for Z I can go a long way by using parallel strategies for roughing and thus removing the need to change direction as much.
Currently I’m using waterlines to keep Z movement to a minimum.
(X,Y,A drivers have been replaced after 2 of them burned up. Z still has the original driver. Thus I’m limiting the load I put on it until the replacement arives.)
Actually the cutting speeds and depth are determined by noise level and neighbors.
Aparently noise is determines primarily by RPM, secondary by cutting depth.
So shallow cuts with higher speeds are more tollerable.
#TravelCNC sits on a rubber mat inside a fligth case with Basotect Acoustic foam lining the walls. …and uses a spindle that is hardly any louder then a sewing machine.
…my large CNC on the other hand is another matter.