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  1. #1
    Ok as many of you will know I have been eagerly awaiting the delivery of my new plasma torch, while waiting I have been extensively testing and debugging my new DIY CNC table and it was all going very nicely.

    The torch came this morning so I moved the table into my test area, connected up the ground clamp and powered the system up.

    All went ok, Mach3 was happy, so I placed a bit of test metal on the table, moved to position for a test fire and triggered a quick pierce signal, no cut just a quick pierce at half power.

    That went ok so i went to move the torch back to start position for a cut test, the torch would not move so i pressed the e-stop and restarted, z axis started moving and partial x axis but not Y.

    Killed the plasma supply and reloaded Mach.

    Now it was jumping about randomly as i turned the MPG knob on the pendant and kept throwing "e-stop requested" errors.

    Thinking it might be my cheapo crap pendant, i unplugged it, turned off "run macro-pump" and disabled support for modbus/mpg, I think that was all that is needed to return to normal?

    Then i reloaded Mach and tried again, now it sort of moves but the DRO's are moving like 20mm for every physical mm moved, its very jerky too.

    Pressing home-all, would bring the axes to home but then back off at 1% speed or very slow at least.

    It would also still throw the e-stop requested errors.



    Now, having spent a lot of effort hardening the table against RF, I cant believe I have fried it with a two second pierce?

    No other PC's in the area showed any sign of problem and there was no radio interference.
    This was just a quick pierce at half power.

    Any suggestions at all?
    I'm desperate.

  2. #2
    It sounds like a a bad connection between the PC and your machine so that it's loosing various signals, check the cable and make sure it's secure at both ends.
    Maybe you have a bad connection on the emergency stop circuit that is going on and off fast, check all connections but it may be the switch contacts themselves. To confirm this you could link out the E/Stop right at the bob but be careful it could be dangerous.
    Last edited by EddyCurrent; 06-03-2014 at 04:42 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  3. #3
    What you using for the BOB.?
    I always turn to the BOB first when having troubles like this has often it's the weakist link in the system due to wrongly thinking it does a simple job so cheap will work.!

    Can you try another PC to see if it's frazzled the PP.?

  4. #4
    The BOb was one of cnc4you.uk's items.

    It has been running fine with a pen in the tool holder for weeks, all I did was move it 10' test it and the fire the torch for two seconds.

    i don't see how it can be the bob as that would not affect the dro's which are running way too fast.

    the e-stop circuit is relay isolated so the only thing that could be bouncing is the relay and that's doubtful. It's not the same as an e-stop, that just displays emergency stop button pressed I think, this displays emergency stop requested.?

    its baffling and if it is related to the torch firing then I am at a loss as to what I can do, I spent a lot of effort rewiring it with cup screened cables, star earthing, ferrite blocks and so on, I was thinking it would be impregnable, don't see what more I can do.

  5. #5
    Quote Originally Posted by JAZZCNC View Post

    Can you try another PC to see if it's frazzled the PP.?
    Thats the odd bit, it boots fine, runs fine, loads mach ok, and passes the mach driver test easily still.

    i would expect the BSOD or software load errors/graphics corruption.

  6. #6
    Check the parallel cable from the PC to the bob, is the inner shieldings fubar, even letting it cross the power cables will do that. Its sounds like your problems are to random for it to be a physical interference problem. but interference on the parallel cable would do all of the above.

    you can test this by keeping the cable as far away from the others, but if its the actual connector ends of the cable, it might not show. then place it across some see if its worse.

    If not, ( i suspect it is the above ). check the PC to see if anything is on the same IRQ or interrupt as the parallel port.

    I say the above from experience.....

  7. #7
    Is your electrical system on the end of a long extension ? maybe your earthing arrangements are not adequate.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  8. #8
    I will check the cables out in the morning.

    as it happens, I am running the PC and bob on a 20' extension, I will check the earth as well on that, the plasma is running on a temporary short extension to a wall mounted isolator that is at 180 deg from the PC supply, the two do not cross.

  9. #9
    Quote Originally Posted by Davek0974 View Post
    I will check the cables out in the morning.

    as it happens, I am running the PC and bob on a 20' extension, I will check the earth as well on that, the plasma is running on a temporary short extension to a wall mounted isolator that is at 180 deg from the PC supply, the two do not cross.
    I'm thinking there could be a voltage difference between both 'grounds' at the ends. In a bathroom for example all metal parts are connected together with a decent size earth wire which is then connected to the earth terminal of a ring main for example, I think you could do the same with your setup where all the earths are connected to a 'star point' on your machine frame. However there is a risk of creating a complex circuit, it would be better if all the equipment could be fed locally from the same supply so that the earth wires between them are very short.
    Last edited by EddyCurrent; 06-03-2014 at 10:45 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  10. #10
    I can arrange that pretty easily, the plasma is running off one leg of a TP&N isolator, I can easily run the controls from the same point, same phase of course.

    is the work lead of a plasma connected to supply CPC?

    if not then there is no connection between systems so it should have been ok?

    edit

    just checked and and the ground return clamp is not connected to supply CPC.
    Last edited by Davek0974; 06-03-2014 at 11:02 PM.

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