Correct wire size for servo/stepper motors ? Dummy question

Hi All
I'm just about to order some wire for my never ending cnc project and have thought myself into the ground over the wire sizes.
Have I got this right ?
the DC + V and -V (in my case 45v 7amp servo supply) roughly 1mm or 1.5mm wire
I am using the jmc 180 watt intergrated servos
Now I assume that the DIR + DIR- Pul + PUL- connections on the intergrated driver are signal inputs from the AXBB-e controller which I could use 0.25mm 0.5mm screened wire
and the ALM and ENA contacts are also signal wires that are ok with the thinner 0.25 - 0.5 m wire
My understanding is that the dc supply carries the main current hence heavier wire.
Would I be correct in thinking that on a normal stepper driver the dir and pul outputs carry the power to the stepper coils ? and that cable be rated for the current capacity of the stepper motor (would the total current rating for the stepper wire be divided by how many are wires conecting the stepper) or should the total amp rating of the stepper be used for each wire PUL+ PUL- DIR+ DIR-.
I hope these questions aren't too dopey? What's thrown my brain is the inergrated driver on the servo.
Cheers
Andrew

I’ve never used servos but on my steppers the high power wires are:
Main power + and - to the drive which in my case are 72V. Can be 1-1.5mm2 or larger if you already have some. Just watch out the max diameter ferrule you can use if you go much larger.

4 wires to the stepper motor which drive the coils. These need to be flexible type and ideally a multi core cable with an outer screen. Around 1.5mm2 CY cable is OK.

All other signals like step, direction and enable can be much smaller diameter as they just carry logic signals. Ideally twisted pair for step/dir but I’ve had no issues with just plain cable. Some people use CAT5 cable so you can see the diameter only needs to be small and doesn’t carry any appreciable current. I don’t know this for sure but I would expect small diameter cable is preferred due to lower EMI, as well as being cheaper.

I think on a servo there would be feedback wires and I would expect these to be small diameter too.

I’ve just re-read you post to check I was answering your question and you won’t have 4 wires going to the motor as these will be inside the integrated driver linked direct the the motor.
So I would expect you only have the main high power wires for + and - and the small logic wires for step direction and enable.

Quote:

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Originally Posted by the great waldo

Hi All
I'm just about to order some wire for my never ending cnc project and have thought myself into the ground over the wire sizes.
Have I got this right ?
the DC + V and -V (in my case 45v 7amp servo supply) roughly 1mm or 1.5mm wire
I am using the jmc 180 watt intergrated servos
Now I assume that the DIR + DIR- Pul + PUL- connections on the intergrated driver are signal inputs from the AXBB-e controller which I could use 0.25mm 0.5mm screened wire
and the ALM and ENA contacts are also signal wires that are ok with the thinner 0.25 - 0.5 m wire
My understanding is that the dc supply carries the main current hence heavier wire.
Would I be correct in thinking that on a normal stepper driver the dir and pul outputs carry the power to the stepper coils ? and that cable be rated for the current capacity of the stepper motor (would the total current rating for the stepper wire be divided by how many are wires conecting the stepper) or should the total amp rating of the stepper be used for each wire PUL+ PUL- DIR+ DIR-.
I hope these questions aren't too dopey? What's thrown my brain is the inergrated driver on the servo.
Cheers
Andrew

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In my view.
Myself I would use at least 14AWG cable for the main power.
Next, to make it easier on myself I would look into using a DB15 cable with the ends cut off for the rest, or with a plug-in screw terminal block at the controller end.
This way you can connect all terminals at the servo end and have full options of which controls you wish to connect as and when at the other.
(without having to swap things or add things at the servo as you progress).

I see this as the easiest solution.


I use a standard plug-in DB44 cable (and a screw terminal block) for my larger AC servo drive that runs it's signals at 24v. All signals work perfectly well.

Thanks Daz
Thats a good idea. Routercnc cleared my mind regarding the logic wires so I can organize the wire now.
Cheers
Andrew

Quote:

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Originally Posted by the great waldo

Hi All
I'm just about to order some wire for my never ending cnc project and have thought myself into the ground over the wire sizes.
Have I got this right ?
the DC + V and -V (in my case 45v 7amp servo supply) roughly 1mm or 1.5mm wire

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Yes, 1mm will be more than enough.

Quote:

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Originally Posted by the great waldo

Would I be correct in thinking that on a normal stepper driver the dir and pul outputs carry the power to the stepper coils ?

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No that's not correct, Dir and Step are low current INPUT signals, they don't send anything out. This is the same for steppers or Servos.

It's the Drive OUTPUTS, usually marked A+ A- B+ B- on a stepper or U V W on a servo that are the high current wires. Wire size will depend on motor size and cable length but for a typical 3nm stepper with 3 to 5Mtr cable lengths then 0.75mm/2 to 1mm/2 works fine, don't need anything larger than that.

For smaller servo's 200w to 600w then 1mm/2 to 1.5mm/2 will work, again depending on cable length. For larger servo's it will be anywhere between 1.5mm/2 to 4mm/2.

Hi Jazz
Thanks for your input. I had a look on a leadshine driver and the connections are more obvious. As i'm working on using the jmc intergrated servos the connections to the connectors all seem to be lowlevel (thin guage wire) apart from the 45 volts. It's also noticable by the size of the connectors on the built in driver the power connector has larger diameter contacts. Using normal drivers seems to be more flexible as each component can be selected, wheras the intergrated system while maybe neater on is fixed with driver and motor (although I hope they are properly matched?) I'm willing to give the JMC a test to see how everything works but i'm going to make sure the control box can be adapted for closed loop steppers of which I have a set from steppersonline. Just out of curiosity is 0.25 mm wire going to last longer in a drag chain than say 0.5 mm (thin wire being more flexible vs thicker wire which because of thickness would be stronger but more prone to fatigue because of it's thickness ? or because it's multi stranded wire the thicker stuff works better?
Cheers
Andrew

Quote:

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Originally Posted by JAZZCNC

Yes, 1mm will be more than enough.



No that's not correct, Dir and Step are low current INPUT signals, they don't send anything out. This is the same for steppers or Servos.

It's the Drive OUTPUTS, usually marked A+ A- B+ B- on a stepper or U V W on a servo that are the high current wires. Wire size will depend on motor size and cable length but for a typical 3nm stepper with 3 to 5Mtr cable lengths then 0.75mm/2 to 1mm/2 works fine, don't need anything larger than that.

For smaller servo's 200w to 600w then 1mm/2 to 1.5mm/2 will work, again depending on cable length. For larger servo's it will be anywhere between 1.5mm/2 to 4mm/2.

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There are no driver to motor cables. It's all built in.
There's just:
3 wires for main DC power incl gnd.
10 Wires for controls (step/dir) etc.
5 wires for RS232.
That's it.

So 14AWG 3 or 4 core for main and a DB15 for the rest. That'll do :smile:

https://www.ebay.co.uk/itm/180W-3000...yABEgLdtvD_BwE

I would NOT fancy running these with flood cooling that's for sure :)

Hi Daz

This will be pretty much woodworking (guitar making) exclusively with maybe a bit of light ali brass work, so no real need for flood cooling, that wouldn`t do the wood much good, unless i use a blunt cutter and too high speeds and set fire to some thing !!! I think 14 awg (2mm²) seems a bit thick I think i'll go for 1.5mm² ?
Cheers
Andrew

Quote:

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Originally Posted by dazp1976

There are no driver to motor cables. It's all built in.
There's just:
3 wires for main DC power incl gnd.
10 Wires for controls (step/dir) etc.
5 wires for RS232.
That's it.

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Yes, I knew this but Andrew may also go the Closed-loop route if these don't work out which is why I answered like I did, it also doesn't hurt for anyone else who's watching in the background and might be unsure.!

Personally, I'm not a fan of drivers attached to motors for a number of reasons, vibration, dust, or fluid ingress and heat that will shorten electronics life are some.

Then you have the fact that unless you mount the controller close to the motors you are running sensitive low voltage signal wires around the machine on long wire runs which can basically become an aerial antenna for picking up electrical noise causing all kinds of brain curdling frustrations!
Also, with very long cable runs then you could experience voltage drop and signal loss, etc not good for a stable machine!

Andrew, if running control wires around the machine and through cable chains etc my suggestion is to buy a good quality shielded cable 22Awg (0.35mm) and keep the wire runs short as possible and keep signal cables away from high power cables like mains voltage or high-frequency cables like the spindle. An obviously good grounding in the control box is a must.

Hi Jazz
I got some extra covers for the electronics mounted on the servos that should keep most of the dust out, and i'm going to be ordering lapp screened cable with 0.5mm wire in it. The only thing I have to think about is wether i'm going to need all 10 outs (I don't think so ) as I think dir-pul- and maybe alm or enable 7 wires would do the job the next wire that lapp does 1s 12 core. I still have to run the power +- volts. There doesn't seem to be a ground connection on the servo so it looks like i'll have to make sure the grounding on the frame is solid.
Cheers
Andrew

Quote:

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Originally Posted by the great waldo

Hi Jazz
I got some extra covers for the electronics mounted on the servos that should keep most of the dust out, and i'm going to be ordering lapp screened cable with 0.5mm wire in it. The only thing I have to think about is wether i'm going to need all 10 outs (I don't think so ) as I think dir-pul- and maybe alm or enable 7 wires would do the job the next wire that lapp does 1s 12 core. I still have to run the power +- volts. There doesn't seem to be a ground connection on the servo so it looks like i'll have to make sure the grounding on the frame is solid.
Cheers
Andrew

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I think you're going to be putting too much money into this with cabling.
I'm with Jazz when it comes to not liking the in built units.
A good 4 core 1mm will see you right in terms of the +/- power and grounds and will have other uses if all goes wrong.
A Lapp 12 core is a waste!.
All the signals are doing is turning voltage through the cable on or off I/O. There's barely any current going through them.
Most of my stuff is either using Cat6, Cat7 (ethernet) or DB## type wiring for most signaling (5v & 24v).

If you know for sure you won't need more than 7 wires you could use a Cat6A STP (shielded twisted pair).
A good option for this use ^.
Or even a sheilded DB9. (these are commonly used with inductive switches that use more current than signals afaik).

The above will be a damn sight cheaper than the Lapp!!!!!.

Quote:

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Originally Posted by dazp1976

A good 4 core 1mm will see you right in terms of the +/- power and grounds and will have other uses if all goes wrong.
A Lapp 12 core is a waste!.
All the signals are doing is turning voltage through the cable on or off I/O. There's barely any current going through them.
Most of my stuff is either using Cat6, Cat7 (ethernet) or DB## type wiring for most signaling (5v & 24v).

If you know for sure you won't need more than 7 wires you could use a Cat6A STP (shielded twisted pair).
A good option for this use ^.

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This has got nothing to do with current and everything to do with Signal and cable quality.

Cat5,6 or 7 is completely the wrong cable for this application and will cause him nothing but trouble in time. Ethernet cable is not designed to constantly move inside cables chains and over time it will break. It's fine in the control cabinet or if fixed to the machine but BAD for moving axis and cables.

Andrew:
The I/O cables are low voltage/current so don't need to be high current cables but they DO need to be flexible and screened well, this is why you need a quality cable rather than a stiff brittle cable which is what Cat5 type cable is and don't let anyone tell you differently because it will fail in time on an application like this.

Also, servo drives are far less forgiving than Stepper drives when it comes to stray voltages and electrical noise, the slightest bit of noise will make them twitch and because you plan on using the AXBB-E that doesn't offer differential output signals and the fact you will have very long I/O signal cables makes you wide open to cross signal contamination. Again this is why you need to use quality cable and with good grounding.

If your wire runs are very long I would consider using a differential line driver module to help boost and keep the signals clean.

Lastly and I don't think you mean to do this but I'll mention it just in case because you mention 12 core cables!
Don't run high power cables down the same cable as I/O, use a separate cable for the power.

Quote:

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Originally Posted by the great waldo

There doesn't seem to be a ground connection on the servo so it looks like i'll have to make sure the grounding on the frame is solid.
Cheers
Andrew

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I wasn't referring to power grounding, I was meaning good grounding practises ie: Star grounding and sending the shields to the ground point.

Quote:

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Originally Posted by JAZZCNC

This has got nothing to do with current and everything to do with Signal and cable quality.

Cat5,6 or 7 is completely the wrong cable for this application and will cause him nothing but trouble in time. Ethernet cable is not designed to constantly move inside cables chains and over time it will break. It's fine in the control cabinet or if fixed to the machine but BAD for moving axis and cables.
Andrew:

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Forgot about the chains.
My Cat7 (solid) go from rj45 modules 'attached' to box + machine, then connect to stranded (24awg) from there to equipment. You can get stranded Cat6A but I do use standard wire goimg from the cat7 to the various sensors etc.

However. I forgot about Igus.....

Chainflex CF10
(8x0.25)C (8core) For control. 0.25mm
(3G1.0)C (3core) For power transmission. Or (4G1.0)C (4core).
https://www.igus.co.uk/product/1015?artNr=CF10.10.04
https://www.igus.co.uk/product/1015?artNr=CF10.10.03
https://www.igus.co.uk/product/1015?artNr=CF10.02.08

I doubt their quality will be disputed (at a price).

I was trying to give you cheaper options because you may yet end up ditching these built ins after a bit but.....
If you're going to do it properly I'd suggest you go to Igus. They have loads of different options.

https://www.igus.co.uk/chainflex/unharnessed-cable
https://www.igus.co.uk/

Hi Jazz
Thanks for the input. I will be running extra cable for the power lines and will keep them as far away as possible from the signal lines. I'll be using Ölflex screened cable from lapp. I'll be using plug connectors (Locking) up to the machine and then from the boxes with the connectors hard wired to the motor drivers to minimize the chance of things shaking loose. I'm not really sure if the Alarm connections and the enable connections are required/neccessary. The machine is going to be for home use and not industrial but I would like to make everything as well as is possible even if it costs more (I've got a box full of screwdrivers that were cheap and only usefull for stirring paint, some of them couldn't even get the lid off the paint can!! ) But my trusty old red handled stanley screwdrivers I bought 40 years ago still work fine. Cable lenghts are not going to be very long as the control box will only be a few feet away from the machine (not much room in the home workshop) I'll have a bus bafor the earth in the control box to run all the earths to and leave the machine end of the screened cables screen open (Just earthed at the control box to cut down on earth loops)
Cheers
Andrew

You only really need the alarm signals if you are using slaved motors, in which case it would be silly not to use them if you have them.

Ok Thanks Dean
It'll cut down on uneeded wiring.
Cheers
Andrew