Confirming PSU spec for steppers.

[Rogue]

Looks like you're after an explanation of why, not what...

I would consider the voltage you get from the common formulas (20*V, 32*L^0.5 etc) to be a 'recommended minimum'. You will get better torque at high speed if you use 70-75V, plus seems a waste to get PM752 drivers if you're only going to run them on 42V.

I think that's it. It's easy to ask for the answer (and I often do) but it's sometimes better to ask for correction as a learning exercise.

I agree about the drivers. It was my understanding that the system could be run with lower voltage, I was trying to establish if doing this would lead to an earthshattering change or just knock a few percentage off the numbers. I would prefer to go for the higher-spec drivers and utilise them as best I can.

Ok the calcs you've done are close and correct in some ways but some of what you read I think you miss understood.? The 752s Manuel and 50-70% was referring to current not voltage. So you still need 57V but only 8-9A current.

Yep I got that bit, though I guess I didn't really make it clear. The reduction to 42V or 48V wasn't because I was applying a percentage reduction, I was just observing that several of the CNC places were offering that size of PSU and if I wanted to buy off the shelf then I was limiting myself to what was on the shelf in the first place!

Without knowing more about pitch and what you want to cut then hard to say best route to take.? .. BUT . If the voltage can provide the speed in combination with your screws to give the feed rates you need to cut what you want then it's not an issue really simple has that.!!

Ahah. Of course, the benchmark against which the performance needs to be measured. I was asking the wrong questions again! Not "will it work" (because the answer can only be "it depends") but "what do I need it to achieve?"

For me it would be "Build own to my exact needs" other wise if speeds/feeds it allows are OK use the 48V@12A and save the money.! Certainly wouldn't buy 2x68V@5a has could easily build for less than price one.!!!

I keep looking at it and thinking "that looks quite straightforward", but then I think about plugging it into the mains and I have a vision of mushroom clouds rising over Derby. Some might say it would be an improvement, of course.

I'm going to end up trying to build this, aren't I? Bugger. Well, most of the components are cheap enough,