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  1. #51
    If you want to try a potential quick fix for false trips then try playing with de-bounce in Mach3 Config.

    No substitute for correct wiring but it may get you going untill your ready to re-wire.?

  2. Don't allow much pressure means voltage will be because of high voltages, this died.
    Add capacitor.

  3. #53
    Eddy (and others),

    The topic of earthing and prevent loops is something, which I have struggled mentally with since I built my machine and thought I had it sorted until your extensive post on page 5 of this thread. Also what I have done may be correct for my circumstances, so just to check:

    Firstly my machine is all metal and I have good conductivity right from the cutter tip to the bed (including through the spindle and bearing etc.). Initially when I built the machine I did think I needed to earth the driver/stepper CY cables back to the star point in my control box only (and from that to mains earth) with a separate earth strap from machine to control box star point and also to have the spindle earthed through the spindle cable shield back to the VFD earth point (and again from there to mains earth).
    .
    However I was getting a lot of spurious e-stops and when I disconnected the earth strap from the machine and essentially relied on the spindle to VFD earth they went away i.e. my machine is only earthed at one point in the VFD whilst all the stepper cables are only attached at the control box star point.
    .
    In light of your post I'm questioning that again and would welcome an opinion especially as I also use a circuit making touch plate and cutter when setting tool height/z zero.

  4. #54
    This also mentions plasma machine requirements, I'm not familiar with plasma machines.

    CNCCookbook: Dealing with noise problems
    Last edited by EddyCurrent; 08-03-2014 at 11:45 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  5. #55
    Quote Originally Posted by Washout View Post
    However I was getting a lot of spurious e-stops and when I disconnected the earth strap from the machine and essentially relied on the spindle to VFD earth they went away i.e. my machine is only earthed at one point in the VFD whilst all the stepper cables are only attached at the control box star point.
    This indicates you have some issue in some other area on the machine or in control box as doing this as just side tracked the problem not cured it.
    Noise is a bear to find You could try taking a earth wire from the spindle body back to Earth on the VFD this will ensure the gantry is earthed at least and probably the rest of machine if bearings don't isolate the rest of frame but still not create earth loop as it's not connected to Star point in control box.

    Have you measured frame with a meter to see if it's putting out voltage.?
    Last edited by JAZZCNC; 09-03-2014 at 12:10 AM.

  6. #56
    When you look about some people say connect the screen at both ends some one end this is why I mentioned earlier that if connected at both ends and there is a problem it would be easy to remove one end to see if it improved. VFD manuals show the motor screen connected at both ends but in addition an earth cable is also required, ideally this will ensure that both ends of the cable screen are at the same potential. Screens should not be used as earth connections, metal parts should be connected to earth at a star point for safety reasons. Loop currents flow because there is a difference in potential at each end of the cable, this is due to long cable runs and earth wires of minimum cross section. There is also the issue of earthing the negative side of DC supplies and also connecting them together, again some say this is good while others say it is bad.

    http://ecmweb.com/content/avoiding-p...-cnc-equipment
    Last edited by EddyCurrent; 09-03-2014 at 12:59 AM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  7. #57
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 6 Hours Ago Has been a member for 9-10 years. Has a total post count of 1,834. Received thanks 192 times, giving thanks to others 5 times.
    The big issue is avoiding the creation of ground loops near control loop wiring.
    There is also the issue of distinguising between earthing, and grounding.
    If you look at commercial machines, they usually have seperate earth and ground points. All sheilding goes to earth, with ground being your negative power supply point.
    .
    I know that on my old lathe, the stepper wiring is unsheilded, and the only issue I got was when I connected the spindle sensor shield to the star point. I cut the wire to the sheilding, and never had a problem since (other than the usual usb SS communication issues!)
    On my new lathe, I've kept it mostly as it was. All sheilds/earth points go to the earth terminal block, with all the power grounds going to the relevant ground bar. However it also uses 24V sensors/switches with differential encoders, so it should be very interference proof anyway. The mill will also be using the same setup once I get around to getting it going.

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