1. My Z axis motor (Nema 34 906 oz) is Bi-polar and needs to be wired accordingly to get all 906 oz of holding torque. However it seems you can wire that in series or parallel. What is the preferred method? Advantages, disadvantages?
You will get more holding torque by wiring the motor in series. The downside is that while running, your torque will drop quickly in relation to the speed. Wiring in parallel solves this problem, but increases heat, and decreases holding torque.
--Just to confuse things even more, you can also run it half-winding only. This will decrease the inductance and help with higher speeds, and will not be too much of a decrease in the holding torque.
2. The Bi-polar wiring of that same motor means 8 wires. I’ve seen people simply combine wires at the motor and run them to 4 conductor shielded cabling to go to the controller. Is this correct? Is there any advantage or reason to run 8 individual wires to the controller?
You have already answered this question, but for the record, it really depends on the driver that you have. Most just use the 4 wires, some take all 8. But most just use 4.
3. I realize that the motor wires and the limit/home switches should be wired with shielded cables. It seems to me that any other wire (possibly adding spindle control later) that runs from the mill to the controller should also be shielded. Do any other wires need to be shielded? Like the wires that run from the breakout board to the stepper drivers? Or is that unnecessary?
When in doubt shield it. Of course that's a pain, so a little breakdown follows. Frequency is what causes interference. The building and collapsing magnetic fields in a conductor with a pulsing electrical signal, produces EMI, and induces currents in adjacent wires. Therefore, anything with a frequency, should be shielded. Of course there are two mind sets to this problem, shield the source, or shield what might be affected. Both won't hurt, and in your application, it would be a good idea. The mill to the controller should be shielded, along with the cables from the drivers to the motors(probably your biggest source of noise), but the limits don't necessarily need it. Digital signals are fairly immune to this type of interference, but it's not going to hurt anything to do it. The BOB to drivers are probably ok, provided they are in the same cabinet, and not running close to the motor outputs.
---I had intermittent problems for years with my limits randomly triggering, This was solved when I finally bit the bullet and installed shielded cables to the steppers and the limit switches.
4. I’d like to buy the shielded wire type that has the drain wire. If I’m wiring these motor cables into xlr (aviation style) plugs, where do I attach the drain wire? Do I simply run it to the metal body of the plug, to one of the motor wires, or to its own terminal (which would require a 5 conductor plug instead of 4.
If memory serves correctly, an XLR connector has a tab on the insert to connect the drain to the shell, a solder connection. That way the shell acts a ground, and you have a continuous shield.
---yes, tie the shield drain wire to the tab on the XLR, and make sure that the mating XLR connector is grounded. Float your shields at the motor end.
5. I know I need to use 18 AWG wire for my z axis stepper, and 22 AWG should work for my x,y steppers. I gather that 22 AWG should work for the remainder of the connections between breakout board, controller, limit switches. Will 22 AWG be sufficient for the connections from the power supply too, or does that need to step up to 18 AWG as well?
This question relies entirely on what motors, drivers, and power supplies you are using. 22awg is only good for 1 amp, out of the range of most nema 23 steppers. I would think these would be using at least 2 amps, but really you should look at the output capacity of the drivers, and size the wire to that capacity. That way, if the motor draws too much power, up to the capacity of the drive, you won't have a fire.
---I would be tempted to use the same wire for all motors, and I would use 18AWG. It is heavier and less prone to break than 22AWG, which could be important if you are using typical inexpensive cable, instead of the stuff that is designed for use on machinery.
6. Should I need to install fuses anywhere in this system? I feel like I’ve seen some people setups incorporate this but I’m not sure if it’s necessary or how to go about it.
Absolutely! There should be at least some fuses or a breaker on the input side of the power supply, say 50% more than the draw of the power supply itself. Again, this really goes to the exact setup you plan on using, so these are just recommendations. Fuses or circuit breakers after the power supply, before the drive, is also a good idea. You do NOT want fuses between the drive and the motor! If one were to blow, you could damage the drive and the stepper.
---Geckodrive warns against breaking the DC voltage to the drives as well, "CAUTION! NEVER PUT A SWITCH ON THE DC SIDE OF THE POWER SUPPLY! THIS WILL DAMAGE, IF NOT DESTROY, YOUR DRIVE!" (from the G201 manual). A fuse would have the same effect as a switch, and could damage the drive as well.
