Cnc wiring!

[Neale]

The CY cable I have used has the three black cores numbered along their length so you can identify which core is which at both ends. The third core could be used for an earth but it works fine as one of the four connections for the steppers - electricity doesn't care what colour wire it runs in!

Talking about awg and oz-in motors suggests that you have been looking at US sites. Europe and European suppliers tend to talk about cross-sectional area (0.75, etc) and Nm. It doesn't really matter which system you use but that's why some people use one set of units and some another.

[Cobey3289]

Thanks guys, it seems to make a bit more sense.
In my research, I've just watched a video of a guy wiring his steppers with
Cy cable. He used a 4 core plus earth and didn't use the earth. He did however expose the wires in his control box and connected them to the side of the metal box to earth them. I'm planning on building a Perspex box, so do I still need to earth the cable or can I just use the 3core and earth as my 4 wires?
Thanks
Mick

[Clive S]

Thanks guys, it seems to make a bit more sense.
In my research, I've just watched a video of a guy wiring his steppers with
Cy cable. He used a 4 core plus earth and didn't use the earth. He did however expose the wires in his control box and connected them to the side of the metal box to earth them. I'm planning on building a Perspex box, so do I still need to earth the cable or can I just use the 3core and earth as my 4 wires?
Thanks
Mick

You need 4 cores to connect the motor to the driver in the control box and use use the screen to connect to the ground star point. Also a plastic box is not suitable it is better with a metal box that can be earthed as it will help with the screening.

You will also need CY cable for the spindle

[Cobey3289]

Quite agree, it seems the more you research, the more questions that end up needing answers!

[JAZZCNC]

Quite agree, it seems the more you research, the more questions that end up needing answers!

Which is exactly why you should never buy anything until you know 100% it's correct for your needs. So don't be afraid to ask.

Regards wiring then it basicly boils down to this for CNC.

Anything which carries signals Ie: Motor wires, Control signal wires, Limit switch, E-stop, require shielded or twisted pair cables. With the Shield going back to Single Earth point " Star point".

Other wires which carry power to components Ie: From PSU to drives, power for control, power fro relays etc can all use normal single core cable often called Tri-rated cable. The cable must be sized according to load it will carry but often people will use one size, that being rated for highest load they'll use. 1.5mm/2 will work for most things.

If using VFD for the spindle then they require special treatment in that shielded cable must be used between VFD and spindle even thou not carrying signals. This is because of the high frequencys they use which can creat lots of electrical interference(noise).

[Cobey3289]

Thanks for that jazz.
Stepper drivers and psu's.
I'm going to be running nema 23's 425oz 3amp. What stepper driver should I use? Some are rated up to 3amp and some more and then they are rated voltage wise. Until I decide on steppers I'm assuming I should hold off on psu's.
I see some people use 2 psu's driving two motors each. Can I just use one for the motors and a 5v supply, or is it best to use one for motors, another lower rated for fans etc and a 5v for the board?

Mick

[JAZZCNC]

Thanks for that jazz.
Stepper drivers and psu's.
I'm going to be running nema 23's 425oz 3amp. What stepper driver should I use? Some are rated up to 3amp and some more and then they are rated voltage wise. Until I decide on steppers I'm assuming I should hold off on psu's.
I see some people use 2 psu's driving two motors each. Can I just use one for the motors and a 5v supply, or is it best to use one for motors, another lower rated for fans etc and a 5v for the board?

Mick

Well it's little more complex than just amps.?
Not all steppers are equal and even thou may be rated same size doesn't mean they will perform the same. Inductance rating of the motor is very important to how well stepper will perform with a given voltage.

For instance, motor with high inductance will spin much slower than one with low inductance using the same voltage.
So if the steppers you buy have high inductance it will mean you'll need to run them with much higher voltage to get the same speed as Low inductance motor.

Then you have how the motor phases are wired. Steppers tend to come in two flavors. 4 wire and 8 wire.
4 Wire motors are less flexible because their phases are predefined at the factory. Often their phases will be series wired.
This means they will require much more voltage to achieve high speeds. Parallel wired motors, on the other hand, will reach same speeds with less voltage.
Often you'll find Series wired motors on Mills or machines which require high torque but less speed. This is because they produce higher torque lower down the rpm range but quickly lose torque as RPM's rise.

Parallel wired phases, on the other hand, give less low down torque but carry more torque higher up the rpm range. This is why parallel is preferred for routers.

8 wire motors allow Either series or parallel phases so again are preferred and easier to find than 4 wire parallel wound motors.

Voltage is the key to getting speed from stepper but at same time too much voltage can lead to over heating and resonance issues.
So this brings us back to inductance and why it's important. Lower inductance means higher speeds can be got with less volts and less volts equals less motor heating, less resonance etc.

So to answer your question about Drives and PSU will require knowing more about the motors. Would also help to know more about the machine spec and what you intend to do with it.

However if you want proven setup which works with most small to medium sized routers then the spec below works great.

Nema 23 3.1Nm 4.2Amp 8 wire motor wired parallel. Ideally with Inductance around 3mh or less.
Digital drives with voltage between 70-80V. Leadshine AM882 are great drive.
PSU with 60-68Vdc output depending on drive voltage. Current will depend on #motors and PSU type.

Now the Psu is little more involved because several types but the best solution by far is unregulated Toroidal PSU. It's gets little involved to why best but trust me this is the best setup for stepper motors. If really want to know why I will explain.

The reason you have probably seen people use 2 psu's is because they have bought off the shelf units which have limited current output so not enough to power 4 motors.
However the best solution is to build your own PSU which is very easy to do and doesn't require degree in electronics. We can help you with whats needed and will say if you can't wire this then you can't wire any of the machine it's that simple.
This way you get exactly what you need in terms of voltage and current in one setup and will work out cheaper than buying off the shelf units.

You will need a separate linear PSU for the Control etc and these are best bought off the shelf and cheap enough not bother building.

Hope this helps.