UC300ETH: UCBB Vs UB1 breakout board ?

[dazp1976]

OK yes I can see how that would work. For info, I have been emailing Balazs at CNCdrive today and he has been replying pretty quickly. Impressive given it is Sunday afternoon/evening, and a bank holiday (in the UK at least) ! Anyway I asked what would happen if 2 stepper drivers were connected to a single step/dir output E.g. if I went with the compact AXBB-E route which can drive 4 stepper drivers as standard, and connected both of my 2 Z step/dir to the same output to drive a total of 5 steppers. This saves the additional BoB, ribbon cable etc. In this scenario I would have:

1: X axis
2: Y axis
3: Z axis & 2nd Z axis from same step/dir outputs
4: A axis (slave for X axis)

The answers from him were when using one output to drive 2 stepper drivers:

Beings you're talking about a Z axis. My assumption is you won't need it ridiculously fast.
It is my understanding that another option is you can run 2 steppers from a siingle driver as long as you follow ohms law.
So example if you have 2 steppers rated at 4A, you can safely run both together using a 8A capable driver so you can up the running voltage Thus only needing to use one axis output from controller.

A little research needed on this other option.

These diagrams are in series. Apparently run better with higher voltages due to it being shared.
They look slightly different so I assume one will spin both in same direction, one will spin them in opposite directions.
Can also run parallel which shares current so then needs higher amp settings.

[Kitwn]

Beings you're talking about a Z axis. My assumption is you won't need it ridiculously fast.
It is my understanding that another option is you can run 2 steppers from a siingle driver as long as you follow ohms law.
So example if you have 2 steppers rated at 4A, you can safely run both together using a 8A capable driver so you can up the running voltage Thus only needing to use one axis output from controller.

A little research needed on this other option.

These diagrams are in series. Apparently run better with higher voltages due to it being shared.
They look slightly different so I assume one will spin both in same direction, one will spin them in opposite directions.
Can also run parallel which shares current so then needs higher amp settings.

Looks good to me. The top diagram will run the motors in opposite directions, the bottom one will not.

With the coils in series you only need a 4A rated driver for two 4A motors, it's the same four amps in both coils. Problem is they only get half the volts each so you won't get as much torque at speed (you can also interpret this as twice the inductance for the same voltage). An 8A driver would allow the motors to be connected in parallel but you cannot guarantee exact current sharing and so the risk of one motor stalling while the other still runs is possibly increased. My money would be on separate drivers being fed the same step and dir signals. If you're worried about having enough current then the signals could be buffered easily enough. A quid's worth of MOSFETs and a resistor or two should do the trick. This leaves you without auto-squaring, which you say you don't need anyway, but seems no different from using a slave axis but only one homing sensor.

The other option is to use one big driver and one big motor driving both ballscrews with a belt.

Kit

[JAZZCNC]

It is my understanding that another option is you can run 2 steppers from a siingle driver as long as you follow ohms law.
So example if you have 2 steppers rated at 4A, you can safely run both together using a 8A capable driver so you can up the running voltage Thus only needing to use one axis output from controller.

Not a good idea because while the drive can handle the loads they can't handle other aspects of driving the motor like resonance compensation, the drive doesn't and can't know which motor is causing resonance so, therefore, can't apply any correction to the correct motor, also the correction applied would be all wrong because it's getting mixed signals. The upshot is a very rough running motor's.