You must see this nice CoreXY machine from Jim Fong (https://plus.google.com/u/0/114592551347873946745) !
Running on grbl-LPC 1.1f (CoreXY) with
60,000mm/min (1000mm/sec) speed
10,000mm/sec^2 acceleration
Automation Direct nema17 76oz-in stepper motors
10 microstep
Parker E-DC stepper drivers
42volt power supply
https://www.youtube.com/watch?v=PYkcFCs6ZFg&feature=youtu.be