Max current for blackbox is 2.4A before switch off..?

Yes, if you'll do a bit of research you find you cannot use an ammeter to check current in stepper wiring.

 

@Peter Van Der Walt is the resident authority on the BlackBox (as he designed it) and he is the only person who can answer such questions.

 

As every environment, machine, ambient temperature, extra resistance from any wiring between controller and motor, mounting position, coil inductance and other motor characteristics all vary wildly - its kinda pointless to go scientific about it.

You dont NEED every single Nm of torque from the motor either, running it with "just enough power" is better for all the components (they don't overheat, they last longer, the wiring doesnt heat up, coil insulation in the motors doesnt crumble, etc) so I always recommend running in your machine over a couple sessions - give it enough power to never stall under normal workloads, but well below overheating.

The drivers on the BlackBox are twice as strong as the typical DRVB8825 boards, so if you were used to those you'd be tempted to want to put all the power on. But a) its much more powerful and b) the potentiometer is scaled from 1.2A at minimum, not 0 (so even 1/4 turn is already enough for most NEMA23s)

If you suffer torque issues, note the SPAM motors may be less than ideal (current rating is but one parameter. Inductance and Coil resistance (and calculated coil voltage from V=I*R of coil resistance and current rating of datasheet does not provide it) - our motors were picked over years of testing to ensure all those are optomised for our kinds of machine. The knockoff's likely just took the cheapest NEMA23s and stuffed them in a box (;