Need some guidance on which wire I need to use.

[mactec54]

That is definitely a good option. I will have to think about it. I may just cut the steel plate and be done with it. That way I can tap all the holes and everything will be very secure and grounded.

Can you show me an example of a clamp/collar that would work to ground the shielded 4 conductor cable for the motors to the plate? There seem to be many different types and I want to be sure to get the correct kind.

Thanks!

That steel plate will be heavy, and way over kill for what you need to do, it could have a problem with rust which you don't want for something like this, it can't have any scale or rust on the steel, that is why aluminum is better, galvanized or zinc coated sheet can be used also

[Sray]

That steel plate will be heavy, and way over kill for what you need to do, it could have a problem with rust which you don't want for something like this, it can't have any scale or rust on the steel, that is why aluminum is better, galvanized or zinc coated sheet can be used also

Very good point. Although it should not be in an environment that is conducive to rust, I would rather not have to deal with it if somehow it did start to rust.

I am looking into aluminum sheets but am not sure which aluminum is good for electrical conductivity. The internet is so contradictory on this. I think 1100 is a good choice. I have also read that 6xxx and 8xxx are also good. I have a metal yard near my house that sells 5052 aluminum sheet in 1/8". I have read that it is used for electrical enclosures but I am not sure of its conductivity. Does anyone know if this will work for a ground plane?

[Sray]

I have found a little info on the electrical conductivity of 5052 but not sure what the numbers mean and if it will work for a ground plane. What I have found is that 5052 has a 33-35% IACS rating. Can anyone tell me if this is sufficient for a ground plane.

[peteeng]

1000, 5000 & 6000 series are fine for a ground plane. 7000 will corrode so don't use that. Peter

[Sray]

1000, 5000 & 6000 series are fine for a ground plane. 7000 will corrode so don't use that. Peter

Thanks Peter! Exactly what I was hoping someone would tell me.

[Sray]

Unless the stepper motor lines are ran together with sensors etc, twisted conductors should be sufficient, the EMI is self canceling when this is done.
Al.

AI,
I found this statement of yours on another post about shielded cables for the motors. In my research I am finding a lot of these CNCs are running unshielded twisted pairs for the motor connections. I am wanting to understand this a little better. On my machine, and probably a lot of machines out there, most of the motor cables will converge at some point before entering the control cabinet. On my machine (4'x4') I guesstimate that 3 of the cables would run together for about 10'. The 4th cable would converge with the other 3 cables for the last 5' or so. Should I try to run them separately into the cabinet? Not sure this is really possible since two of the motor cables are on the moving gantry and would need to be ran in the same drag chain. I suppose if I gave it some thought I could get creative. How far apart would they need to be from one another?

Also when you say "with sensors", what sensors do you mean? Are you meaning endstop sensor cables being ran along side the motor cables? If so, what if the endstop cables were shielded? Could the motor cables be unshielded and be ran together with the endstop cables? Or if the endstop cables were ran separately could the unshielded twisted pair motor cables be ran together without interference with each other?

I am just trying to wrap my head around this. I want to know if I could just do unshielded twisted pair cables as they are much easier to source and a lot less work trying to ground them correctly.

Also I assume that using the aluminum ground plane/plate is best either way?

Shawn

[peteeng]

Hi Shawn - The DC circuits within themselves do not require shielding or twisting. I use single core ,2 core or 4 core wire (untwisted and unshielded) for most of the DC wiring plus good earthing. The issue is high frequency AC ie the line from the AC inverter to the spindle. This can induce stray currents into nearby wires causing all sorts of glitches. So its very important to deal with the spindle wires either by separation (my inverter manual says 150mm separation from memory), twisting or by shielding and earthing or all of these. On a couple of my past machines I've used 12 core and 16 core wire and have run everything through that "one" cable including 230V 50htz AC to a router and have never had an interference issue. Some people have run their AC spindle on unshielded 4 core with no issues, its a bit of luck and good earthing and that can work. Some multicore cable is twisted pairs others are untwisted.

Place an EMI filter on your power-in side of the inverter to stop induced currents travelling back from the inverter into your power system as well. Keep investigating and also don't over think it too much. Get the wiring done and sort issues as they arise vs trying to cover all bases up front first, this can be a path to mild madness.... Keep at it... Peter

[Sray]

Hi Shawn - The DC circuits within themselves do not require shielding or twisting. I use single core ,2 core or 4 core wire (untwisted and unshielded) for most of the DC wiring plus good earthing. The issue is high frequency AC ie the line from the AC inverter to the spindle. This can induce stray currents into nearby wires causing all sorts of glitches. So its very important to deal with the spindle wires either by separation (my inverter manual says 150mm separation from memory), twisting or by shielding and earthing or all of these. On a couple of my past machines I've used 12 core and 16 core wire and have run everything through that "one" cable including 230V 50htz AC to a router and have never had an interference issue. Some people have run their AC spindle on unshielded 4 core with no issues, its a bit of luck and good earthing and that can work. Some multicore cable is twisted pairs others are untwisted.

Place an EMI filter on your power-in side of the inverter to stop induced currents travelling back from the inverter into your power system as well. Keep investigating and also don't over think it too much. Get the wiring done and sort issues as they arise vs trying to cover all bases up front first, this can be a path to mild madness.... Keep at it... Peter

Thanks so much for breaking it down further for me! That was one of my next questions, whether I can use the untwisted multicore cables. You have answered that for me.

Since I am starting off with running a router on my CNC, I do not have as much of this to be concerned with, correct? Once I add a spindle/inverter then I will need to make sure I pay attention to how it is introduced into the system?

[Al_The_Man]

One advantage of using twisted cables that carry significant current is the inherent self characteristic in the cancellation of (radiated) EMI

[peteeng]

Hi Shawn - Correct if your not using an AC spindle then the wiring can be much simpler. Good 4 core solutions are to use 3 phase power cable, 2 or 4 core heavy duty speaker cable. Keeps the wires organised vs single wire instal. But single wire is cheapest. Pay attention to good earthing... Peter

Pro Audio Speaker Cable - 4 Core - Sold per metre | Jaycar Electronics

If you intend to use an AC spindle down the track make sure things like the cable track are big enough. A shielded 4 core cable is considerably bigger than a plain 4 core plus if you use water cooling you will have 2x8mm tubes as well to squeeze thru..... Peter

[Sray]

I decided to start with 18g 4 conductor (non-twisted/unshielded) cable for my motor cables. If I have issues with noise I will go with twisted pairs. But since I am not running a spindle I figured I would start here.

I plan to use 20g wire for all the other low voltage wiring in the cabinet. Does anyone see an issue with this? I am pretty sure the specs of the wire is more than sufficient for all the connections.

In the pic you will see all the components I have so far. What else do I need? While researching other builds I notice their cabinets have many other components as well. I am not sure what they all are. I do see some breakers (not sure exactly what they are for or how they are hooked up), E-STOP button, cabinet lights (green/yellow/orange), EMI/RFI filters (not sure if I need these if not using a spindle/inverter. If so, where?).

NOTE: I have an aluminum plate on its way to replace the MDF.

[peteeng]

Hi Shaun - mo piccy? Peter

[Al_The_Man]

NFB = Non Fused Breakers, these are often used in the place of, or intended for local circuit protection and isolation of a particular circuit.
Did you find any link for the NFPA79?
Proper wiring and running of conductors is usually one of the most overlooked feature of DIY equipment, Usually neatness, traditional location of various devices in a control cabinet together with proper running of conductors generally also aides in keeping interference faults etc, to a minimum.
Current versions of NFPA79 also show typical layouts of enclosures.

[Sray]

Hi Shaun - mo piccy? Peter

Sorry Peter. Not sure how to get it to show. I attached it and could see it when I previewed the post but apparently it does not work that way. I also tried [img][/img] but that didn't work either.

[Sray]

Did you find any link for the NFPA79?
Proper wiring and running of conductors is usually one of the most overlooked feature of DIY equipment, Usually neatness, traditional location of various devices in a control cabinet together with proper running of conductors generally also aides in keeping interference faults etc, to a minimum.
Current versions of NFPA79 also show typical layouts of enclosures.

I tried finding the NFPA79 but I guess it is not available for download unless you buy it. I would like to lay out my enclosure properly if I can. To be honest I feel like I am getting more confused the more I research/learn.

NFB = Non Fused Breakers, these are often used in the place of, or intended for local circuit protection and isolation of a particular circuit.

I will look into those. Where exactly would these go?

I am starting to think my panel will not be big enough.

[mactec54]

I tried finding the NFPA79 but I guess it is not available for download unless you buy it. I would like to lay out my enclosure properly if I can. To be honest I feel like I am getting more confused the more I research/learn.



I will look into those. Where exactly would these go?

I am starting to think my panel will not be big enough.

If you are using a Cabinet of some kind, you would first have a disconnect (Safety Switch) at the Power entrance to the Cabinet, the Power supply from the Switch would go to a Breaker, then from the Breaker to say a DC Power supply, the Breaker needs to suit the amperage of the Power Supply Plus 125%, so a Breaker is used to protect any circuit you have, so if you have multiple different circuits they will all require a Breaker or Fuse Protection, Breakers are easier to add to a circuit, easier to reset or isolate a circuit, when needed than using Fuses

[Al_The_Man]

I tried finding the NFPA79 but I guess it is not available for download unless you buy it.

Here is a 2007 copy.

[Sray]

If you are using a Cabinet of some kind, you would first have a disconnect (Safety Switch) at the Power entrance to the Cabinet, the Power supply from the Switch would go to a Breaker, then from the Breaker to say a DC Power supply, the Breaker needs to suit the amperage of the Power Supply Plus 125%, so a Breaker is used to protect any circuit you have, so if you have multiple different circuits they will all require a Breaker or Fuse Protection, Breakers are easier to add to a circuit, easier to reset or isolate a circuit, when needed than using Fuses

Thanks for that info. I am in the process of drawing up a electrical panel diagram so I can see what I need and where it goes so that it all makes sense in my head. I will try to add the breakers and the E-STOP to the diagram. I will start a new post once I get it done so I can make sure everything looks correct before I start putting it all together.

I cancelled the order for the aluminum plate and just ordered a 20" x 24" x 9" electrical cabinet. It won't be here till late next week so that gives me time to work out the diagram and order in whatever parts I need to install.

Thanks again for trying to dumb this down for me. Much appreciated!

[Sray]

Here is a 2007 copy.

Thanks for the copy. I will be reading through it as I design my cabinet.

[Al_The_Man]

[QUOTE=Sray;2528810
I cancelled the order for the aluminum plate and just ordered a 20" x 24" x 9" electrical cabinet. It won't be here till late next week so that gives me time to work out the diagram and order in whatever parts I need to install.

[/QUOTE]

There is a inescapable rule, that any enclosure or cabinet purchased ends up being at least 5% too small !