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  1. #41
    Yes the spindle is only 0.8Kw but most of the cutting I will do is balsa and up to 6mm birch ply. I could have bought a 1.5Kw spindle for less money with a 1 year warranty but the bearings had only 6 months warranty. So I went for a certificated german 4 bearing spindle with a two year warranty including the bearings so no worries for 2 years and the vfd has a 3 year warranty.

  2. #42
    One of the worst things with electrical systems is that as long as they are working everyone thinks they must be okay. Also with regard to the VFD and spindle, they would still work with speaker cable. It's only when things go wrong that the difference between a proper installation and something less becomes evident.
    Of course as people keep saying it's only DIY so we can just do whatever we want.
    Last edited by EddyCurrent; 10-01-2014 at 08:46 PM.

  3. #43
    Well after fitting up my new spindle and VFD with shielded cable which turned out to be easier than I thought. I have turned a good running machine into one that has lots of Interference with e stops and missed steps.

    Now I know I built the machine with normal wire ( not shielded ) but I was told after it was all wired and ready to plug in that it should have been wired with shielded cable, So now I have to rewire it.
    Now just to check 0.75mm/2 4 core cable for the stepper motors and 0.75mm/2 2 core cable for the limit stops. Is the anything else that I need before sending a order off?
    Do you have to fit shielded wire from the power supply to the breakout board and to the drivers and the drivers to the breakout board or is it just the limit switches and the stepper motors?

  4. #44
    Generally where there is high frequency you need screening, so that means from PC to bob, bob to stepper drivers, stepper drivers to stepper motors, VFD to spindle motor.
    I used CAT5 twisted pair for the bob to stepper drivers, CY cable for stepper drivers to stepper motors, CY cable from VFD to spindle motor. Some have said that CAT5 is not flexible enough to run through the energy chain but that depends on the bend radius you have and the type I'm using is stranded not single core.( CAT5 bend radius it's usually considered to be 4x the diameter). Failing that a different twisted pair flexible cable would do. I also used the same twisted cable for the limits as I bought a roll of it, it's the twisting that helps it reject noise.

    It's a double edge sword, on one hand you are trying to prevent interference entering the cable and on the other hand you are trying to prevent interference escaping the cable. In general for the first issue screens have been connected at one end only and usually at the same point, hence the term star earthing. For the second issue screens are connected at both ends to meet the EMC regs. So with that in mind are your cables interference generators or receivers, I would say they are all generators except for the limits which are receivers. This implies screens are connected at both ends for everything other than the limit cables. At least then if you do suspect problems you can simply disconnect one end of the screens to see if it helps.

    This is worth a read
    http://www.nexans.co.uk/eservice/UK-...3_PBE_V2_1.pdf

    Though aimed primarily at music applications this is also a wothwhile read.
    http://www.phmusic.co.uk/pharri5833/oneend.htm
    Last edited by EddyCurrent; 21-01-2014 at 02:12 PM.

  5. #45
    Thanks Eddycurrent,
    I have my spindle screen connected at the VFD end only, should I connect the screening at both ends the VFD and the spindle?
    I did twist all wiring when I built the CNC router as I knew this helps with screening but since I am going to totally rewire it I am going to make sure that it is properly done so that there is no chance of interference again.
    Another question is, there is eight wires at the stepper motor four pairs, there would be no screening the last few inches or would you add some screening or will it matter for the last few inches?

  6. #46
    Any VFD manual will show the motor screen connected at both ends.

    Generally it's okay to have the last few inches unscreened becasue somehow you have to get the individual cores into their respective terminals, but you could use something like this
    30504 - WURTH ELEKTRONIK - SLEEVING, COND-NYLON, PER M | Farnell UK

    Most people use Gremflex just to keep it tidy.

    If screened cable is not going to be terminated into a special gland made for the purpose I like to use about an inch of heat shrink sleeving at the end, 1/2 onto the outer sheath of the cable and 1/2 over the inner cores, this keeps the end of the screen tidy and stops it fraying or straying. Mostly it's a good idea to solder a short piece of wire to the screen at the end, this joint is hidden under the heat shrink and makes for an easy way to terminate the screen.
    Last edited by EddyCurrent; 21-01-2014 at 04:11 PM.

  7. #47
    Just to get this clear.
    I have used CY 4 Core 1.5mm/2 cable from the VFD to the spindle, But I need to connect the screen to earth not just at the VFD but also at the spindle.
    I will fit CY 4 Core 0.75mm/2 cable from the drivers to the stepper motors also the screen will be earthed at the driver end at a star end earth point and at the stepper motor end.
    I will fit CY 2 Core 0.75mm/2 cable from the breakout board to the limit switches with the screen earthed at the breakout board, but the screen not connected at the switches.
    I could use CY 4Core cable between the breakout board and the stepper motor drivers also the screen earthed at both ends.
    All ends will be joined to a common earth point in side the CNC control unit.
    Should I also run a earth cable between the control box and the CNC machine?
    And I will get some sleeving to make the ends tidy, I like that idea.

  8. #48
    Quote Originally Posted by Bush Flyer View Post
    Just to get this clear.
    I have used CY 4 Core 1.5mm/2 cable from the VFD to the spindle, But I need to connect the screen to earth not just at the VFD but also at the spindle.
    Yes

    I will fit CY 4 Core 0.75mm/2 cable from the drivers to the stepper motors also the screen will be earthed at the driver end at a star end earth point and at the stepper motor end.
    Yes

    I will fit CY 2 Core 0.75mm/2 cable from the breakout board to the limit switches with the screen earthed at the breakout board, but the screen not connected at the switches.
    Yes

    I could use CY 4Core cable between the breakout board and the stepper motor drivers also the screen earthed at both ends.
    Yes if the diameter is sensible to do so.

    All ends will be joined to a common earth point in side the CNC control unit.
    Yes, The idea is to ensure there are no voltage differences between any of the screens so a star point is the best way to achieve it.

    Should I also run a earth cable between the control box and the CNC machine?
    Yes the machine must be earthed for safety reasons.

    Like I mentioned earlier if you subsequently have any problems related to this you can always disconnect one end of a screened cable to see if it improves.
    Last edited by EddyCurrent; 21-01-2014 at 10:14 PM.

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  10. #49
    Hi EddyCurrent many thanks for taking the time to help with my simple questions, I can now sort this wiring with confidence now.

  11. #50
    In addition any cables going to a motor, stepper or spindle, should be physically separated from the other signal cables as much as possible and it's not too bad if they cross at right angles, running them parallel is the worst. Of course this is difficult to do especially in the energy chain.

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