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  1. #1
    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

  2. #2
    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.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  3. #3
    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.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  4. #4
    Quote Originally Posted by the great waldo View Post
    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
    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.

  5. #5
    Thanks Daz
    Thats a good idea. Routercnc cleared my mind regarding the logic wires so I can organize the wire now.
    Cheers
    Andrew

  6. #6
    Quote Originally Posted by the great waldo View Post
    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
    Yes, 1mm will be more than enough.

    Quote Originally Posted by the great waldo View Post
    Would I be correct in thinking that on a normal stepper driver the dir and pul outputs carry the power to the stepper coils ?
    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.
    -use common sense, if you lack it, there is no software to help that.

    Email: dean@jazzcnc.co.uk

    Web site: www.jazzcnc.co.uk

  7. #7
    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

  8. #8
    Quote Originally Posted by JAZZCNC View Post
    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.
    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

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

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

  9. #9
    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
    Last edited by the great waldo; 17-10-2021 at 09:09 AM.

  10. #10
    Quote Originally Posted by dazp1976 View Post
    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.
    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.
    -use common sense, if you lack it, there is no software to help that.

    Email: dean@jazzcnc.co.uk

    Web site: www.jazzcnc.co.uk

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