Confirming PSU spec for steppers.

[Jonathan]

Is it better to match up the driver output with the motor rating exactly, or leave a bit of a margin?

In theory you should be safe to run any driver up to its rating, since that's the whole point of a rating, if you can trust it. In reality however it's always best to overrate the drivers if you can, since then they will run at a lower temperature which prolongs the life of the components.

Also intriguing, though how would you establish that? Would it be as straightforward as checking the voltage from each output separately?

Yes - the difficult bit is determining how much of a mismatch would pose a problem.

[Rogue]

In theory you should be safe to run any driver up to its rating, since that's the whole point of a rating, if you can trust it. In reality however it's always best to overrate the drivers if you can, since then they will run at a lower temperature which prolongs the life of the components.

Hi Jonathan, thanks for chipping in again. I'm still aiming to finish this before you finish at Uni so I'll need you to work towards a PhD, should give me enough time.

I was thinking about this from the point of view of the stepper motors (4.2A) rather than the drivers. Either of the two drivers discussed are rated higher than the stepper (up to 5.2A for the DM856, up to 8.2A for the AM882) so there is plenty of margin. My question was whether it's better to run the steppers at their max or give them a bit of a margin. If your answer still applies (which logic suggests it does) then it seems reasonable to set the drivers for a little under 4.2A.