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  1. #1
    Join Date
    May 2015
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    1422

    Anyone got spare shielded four core cable?

    I'm having some issues with the USB breakout on my OmioCNC router disconnecting from the computer when the spindle starts after a couple of hours of runtime, looking to replace the spindle and stepper cables with shielded cable as a likely candidate for the cause.

    But I really don't want to pay Element14 $180 for a 50m roll when I need maybe 10m to do the job. Just wondering if anyone (especially in Perth) had some spare? Or knew where to get it by the metre or 10m length without getting gouged?

    Chasing around AWG17 cores with insulation rated to 300V or more and an overall shield.

    Thanks in advance!

  2. #2
    Join Date
    Apr 2014
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    432

    Re: Anyone got spare shielded four core cable?

    So then is it the spindle that is the problem ,Boy did I have fun trying to fix that I put a filter in and grounded a different way stopped all the interference just thinking out loud.

  3. #3
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    May 2015
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    1422

    Re: Anyone got spare shielded four core cable?

    Interested to hear more if you have the time to explain your new grounding scheme, InMesh.

    There's a fairly decent filter on the input to the VFD block power side but nothing on the control cable and a decided lack of connection to the ground terminal for the motor on the spindle. No surprise there, given what I've been reading on here of late.

  4. #4
    Join Date
    May 2015
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    33

    Re: Anyone got spare shielded four core cable?

    don't want to pay Element14 $180 for a 50m

    Good morning. Sorry no, I don't have any.
    Element 14, are a good supplier, but bloody hell they know how to make you poor. Then again they did have some 45 drawer cabinets on special a while back at $16.00 each., delivered. Just double check 'em always.
    First up, how much do need? yes, read the post, Mark. 10 meters.
    If it is some meters, try your Electrical Wholesalers, ALH, Rexel, Haymans, TLE, CNW.
    If it is only a meter or a bit, then make your own. Battery earth leads, are supplied in braided cable, ie, a tube of soft flexible copper wire. Slip your existing cable down the braid and terminate both ends.
    Or Ebay, Tinned Copper Braid: Business & Industrial | eBay.
    Depending on the situation, you may want to sheath the braid in a plastic tube. Use heat shrink or whatever tickles your fancy.
    Personally, I have just used the largest (copper size) screened data cable, with Nema 23 size steppers.
    Just read the 10 meter bit.(who's a boofhead) Now, Elekky Wholesalers, give 'em a ring. If they don't stock it, a few days 'n they'll get in for you.
    have fun, mate.
    Mark Needham

  5. #5
    Join Date
    May 2015
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    1422

    Re: Anyone got spare shielded four core cable?

    I spent a fair bit of my last job doing prototyping work and it was always a case of finding the part specced for what I needed then heading off to RS Components, Element14, Mouser and Digikey to see who was cheapest or had quick stock.

    Usually, we *****ed and whined about RS Components pricing until we saw the Element14 prices. But you're right. In the case of this cable, E14 were about a hundred bucks cheaper than RS.

    I had a look at a few of the wholesalers and they all came back at reel prices in the multiple hundreds too. Nice idea on the home-made cable but, to be honest, it's one or two steps more DIY than I can be bothered with - if it comes to a choice of that or paying $50 for a 6m length on eBay I'll just buy the reel and be done with it. The rest will probably "come in handy one day", like all the other crap I have stacked up against the side of the house. And to be fair, I don't know what annoys Her Ladyship more - the pile of "junk" (I call it "stock"), or the fact it does get used eventually!

  6. #6
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    May 2015
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    33

  7. #7
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    May 2015
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    1422

    Re: Anyone got spare shielded four core cable?

    Geez dude, I appreciate your having a look!

    Close but no cigar, though. Might be ok for the steppers (although 22AWG seems a bit light) but definitely not enough meat for a 2.2kW spindle from what I can make out. But he's got other listings there which I will definitely check out, they look pretty good.

    Cheers!

  8. #8
    Join Date
    Apr 2014
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    432

    Re: Anyone got spare shielded four core cable?

    My steppers are 4 core shielded $3 from Homann designs and the $6 shielded 4 core for the Spindle .The first one has a really flexible thick cover seeing as there are two of them running down the cable tray and chain also shared with the Spindle cable they bend well $40 for the larger one a few meters was well worth it.

    I have in the past short changed myself on things that matter not this time nice electrics nice cable and she runs very well I don't have to keep thinking is something going to fail .Your Question about the earthing ,I thought that because I had all the electrics in the one box ,VFD control Steppers power supplies the lot that that was causing the creep in the two steppers when I turned the VFD on but all it turned out to be was I Isolated the metal body of the spindle so it was not to ground and the noise from the motor and VFD caused the stepper to creep .

    There was one other thing because had taken the earth off the spindle motor trying to find this problem I was getting 18V ac to the Jacket of the motor so I earthed the one end of the braided cable to
    the motor the other open so I did not create a closed loop ,In the end motor case to ground cable shielded to ground and it cured all the problems along with an inline filter . Hope this kind of helps VFD's get a lot of flack but it is curable .

  9. #9
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    May 2015
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    1422

    Re: Anyone got spare shielded four core cable?

    I found a bunch of aluminium chips on the disconnected 4th axis plug yesterday and I'm hoping against hope that this was causing partial shorts and similar issues leading to the problem.

    Grasping at straws, I know, but I'd be spewing if I went to the trouble and expense of a re-cable only to find it wasn't needed in the end. So we'll see.

    But if it does turn out to be interference I have the makings of a plan now. Thanks very much for that. Question: did you end up leaving the motor case electrically isolated from the frame?

  10. #10
    Join Date
    Apr 2014
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    432

    Re: Anyone got spare shielded four core cable?

    Sorry for my sometimes illegible ramblings,I did earth the case in the end ,well all the frame work and housing I made in aluminium so everything in the beginning was earthed .So I was trying to eliminate things as I went and forgot this was Isolated see the the braided cable (now only earthed at the motor end ) problem solved.cheers John.
    Attachment 290900

  11. #11
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    May 2015
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    1422

    Re: Anyone got spare shielded four core cable?

    I get it - did you run the 4th lead in that cable to the earth terminal on the VFD and clamp it on the spindle somehow too?

  12. #12
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    Apr 2014
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    432

    Re: Anyone got spare shielded four core cable?

    Oh yes at first I earthed on the Spindle with the 4 th wire and then back to ground ,when I noticed things were moving when the spindle fired up I took the 4 wire off the spindle altogether and just earthed the braid to the spindle cover that's when it stopped completely (remembering I took the insulation from around the spindle body that I put there ) after that .It's difficult to get definitive answers for questions I have hunted for countless hours with little success.I have read about people having trouble with noise moving things all over the place to give an indicator I did just that I moved the VFD 3 meters away now I have the VFD rite next to the X,Y,Z, outputs and cables 20mm gap and it runs like a charm her is the Box with all the bits jammed in .
    Attachment 290908

  13. #13
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    May 2015
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    1422

    Re: Anyone got spare shielded four core cable?

    Thanks again, InMesh - great to have a bit of a heads up of what to expect and what to look for if I need to go down this road.

    Sweet!

  14. #14
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    Apr 2014
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    432

    Re: Anyone got spare shielded four core cable?

    That's OK I think I got of to a good start ,the VFD thing is great I tried to get the Homann digi-speed to run on my BOB but alas all the setup in Mach I did not succeed not to say you cant I just hooked up a 10K trim pot off the VFD control & there is another 10 hours on the searching net I was having trouble with the limits so in the end I just wired them in ass about so if a wire breaks I wont know could not get it working the other way for some reason I could have won Tats the amount of combinations I used, the table is plenty big enough 2m x 1m .
    there are stacks of other things I worked out I am more than pleased with the set up.cheers John

  15. #15
    Join Date
    Jun 2010
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    4252

    Re: Anyone got spare shielded four core cable?

    Noise problems
    Long haul, but worth it:
    Good copper screening over power and encoder cables.
    Good single-ended earthing of all screening.
    Spindle drive in separate metal box from the DC servo axis drivers and their rather sensitive encoder feedback cables.
    Separation of the power drive cables from the encoder feedback cables (especially on the long-run Z axis).

    PWM control to replace potentiometer
    Standard thing, and Mach handles that just fine. Gets a shade more difficult when the analog input is at -100 V (because that's how my KBWT-26 has been built), but optical coupling of the PWM signal is quite possible. Either buy commercial unit or 'some electronics required'. It works.

    Screened cables
    It can be hard to find the 'right' stuff. However, I am using robust screened 4-core instrument cable for a stepper motor, and that works fine for a small stepper.
    Otherwise, buy a few meters of the cheapest screened cable you can find and break it down to copper braid sheath and 4 good light hookup wires. Keep the hookup wires for later use. Thread 7 A figure-of-eight mains lighting flex inside the copper braid and pat it down. Some plastic braid over the top will keep the copper from touching anything 9and looks good), and you can buy that in short lengths from RS etc. If you need 3-phase, try two strands of figure-of-8.

    Cheers
    Roger

  16. #16
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    May 2015
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    1422

    Re: Anyone got spare shielded four core cable?

    Thanks, Roger

    I'd have thought the screening obviated the need for partitioning down the cable chain but there you go. Star point grounding back at the control box for shielding and all other components? Stepper drive so at least I don't have to worry about interference on the encoder lines.

    Had to laugh yesterday. Here I am, typical hobbyist, b1tching about spending $50 on good cable over a lunch with the missus. Two burgers and a beer each and yep, there's $52 and my cables. Lol.

  17. #17
    Join Date
    Jan 2015
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    23

    Re: Anyone got spare shielded four core cable?

    up,,
    www.dongtai168.com www.dongtai1688.com
    gem processing machine

  18. #18
    Join Date
    Jan 2015
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    23

    Re: Anyone got spare shielded four core cable?

    this is hard to tell
    www.dongtai168.com www.dongtai1688.com
    gem processing machine

  19. #19
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    Jun 2010
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    4252

    Re: Anyone got spare shielded four core cable?

    I'd have thought the screening obviated the need for partitioning down the cable chain
    The copper braid screening will almost completely eliminate any radiated electric fields. However, it will have almost zero effect on any radiated magnetic fields, and motor current draw can create magnetic fields.
    Separate steel boxes will suppress a lot of magnetic fields.

    Star point grounding back at the control box for shielding and all other components?
    Definitely.

    I have just spent several months, on and off, rebuilding ALL the electronics in my CNC. And a lot of the effort was in separation and screening. The KBWT-26 spindle driver was partuicularly obnoxious. In its original state it wiped out any nearby radios with RFI. Much better now. It seems to have paid off.

    Cheers
    Roger

  20. #20
    Join Date
    May 2007
    Posts
    15

    Re: Anyone got spare shielded four core cable?

    Try putting your VFD outside the box your control system is in.

    I upgraded all my stepper and limit switch cable to shielded but still had problems.

    I ended up trying the VFD outside the enclosure (which was not as pretty) but eliminated the problem. I also tried multiple VFD's as the first one I had had issues, but this made no difference to the interference.
    Cheers,
    Hicks

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