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  1. #31
    Quote Originally Posted by EddyCurrent View Post
    Dave, you have 3 power supplies, the 36 volt and 2x 24volt, are the negatives of these connected together ? and are they connected to earth ?
    Ed Have you not noticed he's got it sorted.?

  2. #32
    Quote Originally Posted by JAZZCNC View Post
    Ed Have you not noticed he's got it sorted.?
    Yes but I'd like to understand it more.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  3. #33
    Quote Originally Posted by EddyCurrent View Post
    Yes but I'd like to understand it more.
    Ok well don't see there's much to understand really.? He had an earth loop because of PC case earth and the High frequency and voltage of the Plasma sent the PP mental. . . . . .Simpliz really.!!!

    What you looking for or thinking.??
    Last edited by JAZZCNC; 08-03-2014 at 09:51 PM.

  4. #34
    Yes there are three psu's, an 11A 36v for the motors and drive boards, a small 24v 1/2A one for the safety and control circuits, and a 24V 3A unit for the bob.

    none of the negatives are grounded or commoned, unless done internally but I checked them with a meter from 0v to mains earth and all were isolated it seemed.

    the bob is not commoned to the PC as the screen on the cable does not connect, the screen on the db25 plug is not connected to the 0v rail on the bob either, it has full opto isolated PC inputs.

    the outputs are also fully opto isolated to the drive boards so no common needed there either.

    the safety inputs are also opto but I threw in the relays as an extra measure to keep the low voltages inside the cabinet.

    the safety circuit psu is just a little wall-wart that I threw in when I pinched the good psu for the bob, I could try using the bob psu but that would likely bridge the noisy circuit direct to the bob power supply lines and defeat the object of isolation. I will get another small psu and ditch the wall-wart now it's working.

    cant think of much else to offer really, please do ask if you need more.


  5. #35
    From what I've read so far, it's a bit like milling, the jet prefers to cut one way rather than the other, I'm trying to find the post again because I can't remember if it was clockwise around the outside or anti clockwise, easy to test though.

    its connected with the way the plasma swirls as it exits the nozzle.

    once the first part of the cut passes a bed slat, it's pretty much tack welded down so the contact should be good.

  6. #36
    Oops, wrong thread..

  7. #37
    Well, all is still not well.

    I had some more play time today, tried some 30A test cuts and it's messing about, stopping cut motion midway, throwing e-stops, losing co-ordination etc.

    It will be even worse if i plug the PC into the same extension as the system, I have to run two extension leads back to the wall socket just to get a partial success.

    If it was 100% because i have no ground rod then i would stop testing until I take the machine home where I can fit one, but I'm not totally convinced it is that.

    The system has a filtered plug fitted and the pc has an in-line filter fitted.

    Not sure where to focus my efforts now????

  8. #38
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  9. #39
    Hmm, if i got the chinglish right, I really do need a ground rod, ground the lot to it with the shortest thickest cable I can find and keep my fingers crossed?

  10. #40
    Just had a chat with the suppliers and they feel the generator is not switching to full power i.e. I am cutting (or trying to) with pilot arc power which is about 20A on this model

    They are sending me a new (tested good) hand-held torch for test purposes and while waiting they have advised me to try upping the air pressure to 75psi just for a test.

    But basically at 30A and 1.5mm sheet, it should practically vaporise the damn thing at the slow speeds I have been trying!!

    Will know more tomorrow.

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