Hi guys, greetings from Argentina.
So, im building a cnc router. Right now, while i wait for some mechanical parts, i want to start figuring out the electronics.
What i have:
3 nema 23 steppers: 57sth56-2804a
3 drivers: m542pbf-g
Im triyng to figure out voltage, and driver configuration.
Is there any general info around this?, something to read or any advice?
It is my understanding that you can send 5 to 10 times the rated voltage to the steppers. The current is what you have to pay attention to. Don’t offer them more than they are rated for. Better yet, don’t offer them more than they need to get the job done.
You run as much voltage as your drives can handle, and you can supply. You set your drive current for what the motors are rated at. That is all there is to it really. Well, other than deciding what step sequence you want to use. Generally use the highest sequencing that you can supply a step pulse signal for, and still achieve the speed you want. Although practically even half step sequencing works. Full step mode has always given me resonance problems. Though some high end drives can automatically change the mode they are in to maximize performance at various speeds.
The data files tell’s a lot about the steppers and drivers so read it 
http://www.snasda.com/doc/57STH.pdf
http://www.leadshine.com/UploadFile/Down/M542d.pdf
Its always a good idea to read them.
Wonder why its always hard to read the manuals usealy heheheheheheheh
Have fun
@Paul_M_Tas , i have that info already. I now about the amps, but dont know about what microstepping is recomended, per example. That info doest say anything about full step/half step, etc etc etc.
Thanks for the answers, they are good info!
@Nicolas_Arias
If curious about torque vs. microstepping, does the following help?
Microstepping trades smoothness for speed, basically. I run 1/16 or 1/18 microstepping and it’s slooooowwwwww but it’s actually about the right speed for milling steel. Nice finish, too. If you’re doing wood you may just want to half-step.
@Kent_VanderVelden , great read, thanks! @John_Bump , cool, thats the kind if info i was looking for.
@Nicolas_Arias
Try different modes. See which you like how it runs the best. Quarter stepping is pretty nice. But some motor, and machine combinations may experience resonance with certain settings. The most critical setting of course is to set your drive current output correctly for the motors you are using. After that is is all personal preference, or by ear.
Your biggest challenge will be sizing your PSU for your CNC machine’s requirements. The closer you can come to your drive’s max input voltage (without exceeding it!) the better your motors will perform. You still need to insure that your PSU can always deliver the current you may require though too.
This is the kind of PSU the really hardcore generally run:
It is simple, and robust. There is not much that can be said against it, besides what it costs, and perhaps weighs. Implemented correctly though it is practically bulletproof.
Cheap imported motor, drive, and PSU kits generally come with some surplus SMPS. I won’t say that doesn’t work, but I won’t say it is the best way to go either. The reasons why a SMPS is perhaps not the best choice for stepper driving are too involved for me to go into here, but suffice to say there are reasons against using them.
Perhaps nit picky, the resonance issues are likely more to do with particular speeds. Changing the micro-stepping alters the pulse-speed relationship around, but the potential for resonance still exists near the same speeds. Some controllers can be programmed to avoid speeds known to cause resonance. Some can even identify resonance speeds on their own.
@John_Bump
What step frequency can your system output? If you are only software stepping using a parallel port then that could be a limiting factor at higher microstepping settings.
To run a 1.8 degree motor (200 steps a rev) in 1/16th step mode at 1,000 RPM for instance, you would need to supply a step stream of 53.33KHz Which is beyond what many PCs can really do with just a parallel port.
The motor controllers can take up to 50V - you should get as close to a 50V supply as you can.
Driver stepping does two things - it increases the resolution at which you can direct your steppers and reduces the available torque accordingly.
So, for maximum torque you would use 1:1 stepping, but that may be impractical for your desired cutting resolution.
Taking an actual example: Using M8 leadscrew - they progress 1.25mm/turn. The steppers you are using are 200-step/turn motors, so your maximum resolution at 1:1 is 0.00625mm per step, or 160 steps/mm
I only cut plywood and MDF - that sort of accuracy is absolutely fine. But, 1:1 stepping is noisy and resonates - setting microstepping makes things quieter and smoother, at the expense of less torque. In my case, that’s an ok trade-off. I use 1/8 stepping on a ‘smart’ USB-attached controller board.
What you ultimately end up configuring will have as much to do with your controller and software package - what have you decided to use?