# CNC cables, wire and wiring questions



## architard (Jan 14, 2014)

I’m finally getting around to starting up my G0704 CNC Conversion and after reading blogs, forum posts and watching a ton of YouTube videos, I’m still thoroughly confused about the details of wiring things up. So I have a few questions I’m hoping someone here can address

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?
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?
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?
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.
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?
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.


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## jumps4 (Jan 14, 2014)

hi
  1. wire your 8 wire motor in series it is lower amps and higher speed. torque is "holding" not running torque and does not change.
  2. I would use 18agw shielded wire for everything outside the controller and you shield the high voltage leads in the enclosure and if you keep them away from all low voltage wiring you should be good. wires going from controller to motors inside the case are high voltage and alternating current from 0 to +25v / 80v when pulsing depending on your power supply, and they should be shielded inside the case. the shield wire for the aviation plugs are connected to the housing of your plug if you don't have enough leads to run it inside on it's own pin, then connect it to ground. the case is fine if the case is connected to the green lead (equipment ground ) in your power cord. all grounds come back to the controller case, do not ground shield cables to your mill or you will get ground loops.
 I would at least add a 15amp breaker to the power side to keep any shorts from depending on the house circuit breaker and wall outlet . If something goes up in smoke it's better to be in your enclosure case than your wall socket.
I think that was all your questions
I hope that helps
steve


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## architard (Jan 15, 2014)

Thanks Steve.
That helps a lot. I hadn't even thought about the wires going from the aviation plugs in the case to the drivers. I will make sure I use shielded cable on them as well. 

I see that by wiring the bi-polar motor in series I actually connect 2 pairs of motor wires together so that makes my question about running 8 wires to the controller a moot point. 

So you suggest using 18 AWG on everything outside the controller? Even for limit switches? My XY motors are Nema 23 and it looked like 22 AWG would be sufficient. But I'd rather err on the side of stronger components so that sounds like a good idea. I just didn't think 18 AWG would be required for limit switches. 

Does all the other wiring inside the case need to be 18 or can I get away with 22 there?

Sadly my components are getting delivered today and I don't have any wire to try them out! I should have asked these questions earlier haha. 

Thanks again!


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## DAN_IN_MN (Jan 15, 2014)

architard said:


> Thanks Steve.
> That helps a lot. I hadn't even thought about the wires going from the aviation plugs in the case to the drivers. I will make sure I use shielded cable on them as well.
> 
> I see that by wiring the bi-polar motor in series I actually connect 2 pairs of motor wires together so that makes my question about running 8 wires to the controller a moot point.
> ...




I wired control panels for a bit.  I was told to keep AC and DC away from each other.  If they had to cross paths, do it at a 90° to keep EMF transfer to a minimum.

IMO, the limit switches could be smaller gauge.  Not a whole lot of amps running on those.  I guess it depends on how you buy your wire and how much you will be needed.  If you buy 100' of 18 AWG and that's enough to for all of your runs, use it.


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## jumps4 (Jan 15, 2014)

I use the 18 for everything including the 120v because I bought an entire roll of it.  lol
Lowe's had it by the roll but not by the foot and I could not find it anywhere local.
On low voltage signals the bigger the wire the lower the voltage drop per foot but 22 would work for limits fine there is not current on these lines, it is just sensing connection or no connection.
all the low voltage lines running to the machine can be in the same cable, limits and estop and all the limits can be run off of one pin in mach3
mach3 knows the direction it is moving so when it hits a limit it knows what switch it hit. the only down side to this is it moves one axis at a time to home the machine. if it sent all the axis at the same time it would not know which one hit first.
steve


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## architard (Jan 15, 2014)

Ha, yeah Steve I saw in your build thread that you bought a 100' roll. I kind of figured that's why you wired everything with 18 AWG was because you had enough of it. I'm ordering stuff online so I have a bit more flexibility on what I can buy and I'm trying keep the costs down. Surprisingly I've found Mcmaster Carr to have reasonable prices on shielded cable in a wide variety of lengths to buy it in. 

Again thanks for all the help. 

I'll probably be posting some more about the build in the future. The mill is currently in many pieces as I'm trying to document a full 3d model of it in Solidworks. I still need to address all the hardware stuff, the stepper mounts, and I need to buy ball screws too. Once that's all ready hopefully I can move forward full steam.


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## DMS (Jan 15, 2014)

I have had noise issues attaching shields to metal enclosures or metal backplanes. I had better luck running a ground directly to the earth ground where it enters. Basically attach a separate ground line to a single point as close to the "real" earth ground as possible. 

+1 on others comments as well. I will add that for limit switches, you may want to go with a smaller gauge just because it will be more supple. I have mine set up with CAT5 (not ideal, but it has been running a year and a half). You also want stranded cable for anything that moves. For anything carrying motor power, bigger is better. 18ga should work.


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## jumps4 (Jan 15, 2014)

It would be great If you did a build thread.
A few months back I helped a member ( thebaconbits ) build his g0704 mill here at my shop.
here is a link to his build thread and a video showing the machine completed with enclosure.
the g0704 is a really well built small mill and was easier to convert than my ZX45. I really enjoyed helping him with his build.

http://www.hobby-machinist.com/showthread.php/14548-G0704-build-in-progress?p=133069#post133069


[video=youtube;T6mbrc_ztA0]http://www.youtube.com/watch?v=T6mbrc_ztA0&amp;feature=youtu.be[/video]


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## architard (Jan 15, 2014)

That's a sick enclosure! I do not have nearly the amount of space to build something that big for mine. I have plans on making a sort of aquarium looking box that will go around the table. If you look up CruddCNC on YouTube you'll see what I mean. 

How do you like the harbor freight spot welder? I have often thought about picking one up. 

I might start a build thread soon. I'm thinking of shooting most of the build with video and posting it to YouTube. I'm still on the fence about all that. I usually get so into a project I just don't want to hassle with documenting it all. But I know how much it's helped me seeing other people's builds and if something I posted helped just one person I'd be happy. 

I placed an order for the wires today, and picked up a new soldering station. The box of components is sitting here, but I haven't opened it yet. I realized I don't even have a DB25 cable to play with it yet. Of all the damned old cables I have never thrown out I really thought I had an old scanner cable laying around. Had to buy one of them. Hopefully most of the stuff should be here by Friday so I can play with some of it.


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## Codered741 (Jan 16, 2014)

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. 
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. 
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. 
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.  
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.


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## awander (Jan 16, 2014)

Codered741 said:


> 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.
> 
> ...


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## architard (Jan 16, 2014)

awander said:


> Codered741 said:
> 
> 
> > "*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.
> ...


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## Codered741 (Jan 16, 2014)

awander said:


> ---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.



I have always found this interesting, because, if you study the Geckodrives, there is an integrated fuse within the drive.  ( I have had to replace several)

Regardless, it is important to not break the Negative connection, only the positive side of the circuit, in order to leave a path to ground.  

-Cody


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