Hi,

So I hope it's ok to make a post where I believe I have the answer, but it bugs me too much for me not to ask experienced people to get the definitive answer...

So i have a complete kit from HobbyCNC.com. It consists of:
- A "Pro" board equipped with SLA7078MPR stepper drivers
- HobbyCNC's most powerful steppers (3A/phase, 2.15Nm holding torque, 3.2mH inductance, Vcc= 56VDC <--- I'll get back to this)
- The components to build a non-switching power supply of 36V. HobbyCNC recommends 36V for their board, but minimum 12V and maximum 42V is also within tolerances.

So, my problem is:
regardless of load, which axis I'm running, acceleration, microstepping setting, Vref setting (currently set to exactly what's recommended), my motors will not get up to speed. Anything above 720 RPM and they stall. with the gear/sprocket ratio of my EMCO F1P, this results in a not very impressive travel of 720mm/min (1:5 gearing, and 5mm pitch on ballscrew).

Now, back to the "Vcc" value for the motors, of 56VDC. Doesn't this value tell me that the motors would be better off with a higher voltage? And if so, and this bugs me the most: why did even HobbyCNC sell these motors together with a board that can only handle 42V (and recommend 36V in addition to that..)?

I could switch to a power supply with a 42V output, but how many rpm's would I gain with the extra 6V's?

Might there be anything else I've missed? Or am I expecting to much from my steppers, is 720rpm not too bad? Up to and including 720rpm, they run very smooth, and feel quite torquey.. the reason I expected more was that the machine is from somewhere in the late 80's and was specced to rapid up to 1200mm/min, and it is painful not to at least get the same out of my "modern" setup.

Thanks in advance guys