What current to use for MAE HY200 3424 0310 Stepper Motor?

[Mxml]

Hi, I have a Denford Novamill with a routoutcnc Mach3 conversion - I recently replaced the X and Y steppers and drivers (DM542T's) to solve a lost steps issue - it worked. Up until now I haven't had any issues with the Z but yesterday I got a repeated stall on the Z, so I'm going to replace the driver to see if that helps. I've already slowed down the motors, increased the pulse time etc.

The Z axis has a MAE HY200 3424 0310 which is rated 3.1A. Currently it is running on 2.5A as that is the maximum the routoutcnc driver can output. The new driver is capable of up to 4.2A, so I'm hoping to get better performance out of the stepper once upgraded.

My question is this:

The stepper's documentation says that its rated phase current is 3.1A. Does this mean it is 3.1A per phase, or altogether? If it's 3.1A per phase does that mean 6.2A total if wired in parallel, and I should be alright running the stepper at 4.2A?

Thanks