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  1. #1
    Join Date
    Aug 2005
    Posts
    413

    Dmm fault issue

    I have a plasma table with dmm servos and dyn 4 drives, has a dual motor gantry for Y axis. Built about 4 years ago, worked great until recently when using 65 and 85 amp tips to cut thicker steel one of the gantry motors faults out. Lately has been consistently the Y1 motor. When running 45 amp finecut tips on thinner steel it works fine day after day. It used to cut thick stuff just fine as well.

    I have removed the torch cable from the cable trays it was in next to the motor cables, thinking it might be a noise issue, and still it faults out. Usually Over voltage and within a few seconds of the machine starting to cut. I have re-tightened the motor cables on the connector to dyn 4 cleaned and inspected the connector on motor.

    I tried to manually tune the motor as suggested by the DMM tech a while back and as soon as I put it in sinusoidal test mode, the motor bangs and I get a Lost phase fault. Even with the sin at freq 1 and amplitude of 200, still bangs and faults to Lost Phase.

    I can push the gantry back and forth just fine as I always have been able to. The motors are hooked to precision right angle worm gear boxes so it pushes a little hard but same as it was when new

    I have a spare Dyn 4 drive I could try, or should I be ordering new cables or ?? I see the book suggests a regenerative resistor possibly for the overvoltage issue, but maybe its something else I'm missing yet.

  2. #2
    Join Date
    Jan 2005
    Posts
    15362

    Re: Dmm fault issue

    Plasma Table can be a pain, grounding is usually the biggest problem and the lack of EMI filters

    Regenerative Resistors have nothing to do with is they are only needed for high-speed stopping

    Are you using one Main Power source for your machine??
    Mactec54

  3. #3
    Join Date
    Aug 2005
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    413

    Re: Dmm fault issue

    Yes, one 3 phase feed to machine. I have a line reactor before the power for the drives. And recently tried adding small transformers to the logic power for the 2 gantry drives as DMM recommended as my incoming power likes to run around 247, so we knocked the logic power down to 140 after the little transformers. Problem has been consistent before and after that though. 3 phase comes from a phase perfect digital converter.

    What gets me is 1: it used to work fine on thicker stuff, 2: I get over voltage fault when the torch starts cutting but a lost phase fault when try to tune. 3: I wonder if the bang of the motor when trying to tune signals the issue a bit as it moves fine in step and direction when the torch is not cutting but in rs232 command and sinusoidal test it bangs loudly before faulting out. I have heard this bang before usually when the drives are powered up and then I start the linux command cnc program, just assumed it was resetting something, typically that doesn't fault out though. I usually try and start the program first and then trip the large contactor that turns on the drives and plasma.

    I have a new set of cables ordered and may try a spare dyn4 drive tomorrow. I checked my grounds as well as the ground rod that is under the machine and all connections are tight and clean like they should be and were back when it ran perfect.

  4. #4
    Join Date
    Aug 2005
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    413

    Re: Dmm fault issue

    Ok, finally talked with the DMM tech and we started suspecting voltage fluctuations upstream of the plasma when under load. So of course today when I go to monitor the voltage of the generated 3rd leg out of my DP20 phase perfect it basically runs fine except for one fault right away... I managed to get the parts cut that I needed from 1/4" and have to switch back to some thinner stuff for awhile now.

    Anyway I had my multi meter set on min/max and watching the L3 to ground, normal about 212 max when faulted of 224

    I then switched and measured between L1 and L3, normal 245 and the max I saw with no fault was 258

    So we might be on to something. Atleast I know where to start looking when the issue comes up again. I think I’ll look for some voltage data recorders and try and watch all 3 legs from that phase converter for awhile as well.

  5. #5
    Join Date
    Jan 2005
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    15362

    Re: Dmm fault issue

    Quote Originally Posted by JPMach View Post
    Ok, finally talked with the DMM tech and we started suspecting voltage fluctuations upstream of the plasma when under load. So of course today when I go to monitor the voltage of the generated 3rd leg out of my DP20 phase perfect it basically runs fine except for one fault right away... I managed to get the parts cut that I needed from 1/4" and have to switch back to some thinner stuff for awhile now.

    Anyway I had my multi meter set on min/max and watching the L3 to ground, normal about 212 max when faulted of 224

    I then switched and measured between L1 and L3, normal 245 and the max I saw with no fault was 258

    So we might be on to something. Atleast I know where to start looking when the issue comes up again. I think I’ll look for some voltage data recorders and try and watch all 3 legs from that phase converter for awhile as well.
    That's very strange for the Phase Perfect I would say that this is the supply to the Phase Perfect that is causing the voltage change

    You must have a EMI Power Filter for the logic input this would be after the added Transformer

    When testing a motor or auto turning, it sounds like you have the acceleration set to high, when a drive does fault, over voltage or missing phase, it can be a number of things that can cause this.

    I don't think this is a Voltage problem, it's more a noise problem
    Mactec54

  6. #6
    Join Date
    Aug 2005
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    413

    Re: Dmm fault issue

    It could still be, thats why I want find some data logger and at least know for sure on the voltage side. Without the torch running the machine moves great, sounds great etc, nice and smooth. The tuning settings that have been in the Y1 drive for 4 years are: Main gain- 13, Speed- 6, Int- 3, Torque filter- 127, max accel- 12, max speed 24. IIRC Y2 is identical settings.

    One thing I do notice once in awhile, if servos are on and machine is idle for several minutes, usually Y1 starts to vibrate ever so slightly, enough to make noise. If I jog the gantry back a touch it goes away.

    The other strange thing that has started happening lately is if I turn the magnetic disconnect for the plasma/ drives off (smaller one ahead of that for the computer stuff etc), sometimes the phase perfect shuts down. I have the dp20 setup with a light switch to turn it on/off and I have to go over and flip the switch off and back on again. No fault light in the DP20, just the normal green led.

    The Dmm tech is recommending I just pull the 3rd leg from the servo drives and be done with any issues from the 3rd leg.

  7. #7
    Join Date
    Jan 2005
    Posts
    15362

    Re: Dmm fault issue

    Quote Originally Posted by JPMach View Post
    It could still be, thats why I want find some data logger and at least know for sure on the voltage side. Without the torch running the machine moves great, sounds great etc, nice and smooth. The tuning settings that have been in the Y1 drive for 4 years are: Main gain- 13, Speed- 6, Int- 3, Torque filter- 127, max accel- 12, max speed 24. IIRC Y2 is identical settings.

    One thing I do notice once in awhile, if servos are on and machine is idle for several minutes, usually Y1 starts to vibrate ever so slightly, enough to make noise. If I jog the gantry back a touch it goes away.

    The other strange thing that has started happening lately is if I turn the magnetic disconnect for the plasma/ drives off (smaller one ahead of that for the computer stuff etc), sometimes the phase perfect shuts down. I have the dp20 setup with a light switch to turn it on/off and I have to go over and flip the switch off and back on again. No fault light in the DP20, just the normal green led.

    The Dmm tech is recommending I just pull the 3rd leg from the servo drives and be done with any issues from the 3rd leg.
    Yes, I would be inclined to do the same as you don't need the 3 leg, for what you are doing.

    What plugs are on the encoder cables ?? can you do a photo

    What control are you using??
    Mactec54

  8. #8
    Join Date
    Aug 2005
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    413

    Re: Dmm fault issue

    They are dmm encoder cables for the dyn4 drive. Kinda a metal oblong on the drive side and a plastic clip on the motor side. I have tried ferrite cores on the encoder cables, didn't see much of a change in anything took them off. I still have them on the ethernet cables to the computer I believe.

    CommandCNC with I think DTHC 4 MP3500

  9. #9
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    Jan 2005
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    15362

    Re: Dmm fault issue

    Quote Originally Posted by JPMach View Post
    They are dmm encoder cables for the dyn4 drive. Kinda a metal oblong on the drive side and a plastic clip on the motor side. I have tried ferrite cores on the encoder cables, didn't see much of a change in anything took them off. I still have them on the ethernet cables to the computer I believe.

    CommandCNC with I think DTHC 4 MP3500
    Why I asked about the plugs, this could be a source of a connection problem, I would check all the plug connections
    Mactec54

  10. #10
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    Aug 2005
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    413

    Re: Dmm fault issue

    I'll check them out. I do have a new cable on order, I may just swap it out and see if it changes it.

  11. #11
    Join Date
    Mar 2013
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    66
    Quote Originally Posted by JPMach View Post
    I'll check them out. I do have a new cable on order, I may just swap it out and see if it changes it.
    Did you fix the issue? If so what was the root cause? I am having DMM faulting on power cycle issues.

  12. #12
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    Jan 2005
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    15362

    Re: Dmm fault issue

    Quote Originally Posted by repauli1 View Post
    Did you fix the issue? If so what was the root cause? I am having DMM faulting on power cycle issues.
    Are you using a line reactor and EMI Power Filter
    Mactec54

  13. #13
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    Mar 2013
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    66
    Quote Originally Posted by mactec54 View Post
    Are you using a line reactor and EMI Power Filter
    I have a large router, fighting issues with overcurrent faults when cycling power.
    On a cold start it always starts up fine, but if I cycle power to drives, when Oak and drives come back up, usally 1 or 2 drives fault out. If I power down, let it sit for 30min or so, start up, let it sit for 15minutes then it seems to start up.
    I am using a phase converter, and yesterday I switched power to a different phase converter.. same issue. Any clues?
    Ps: control voltage comes on with power up before oak boots, I do have a 30amp line reactor,individual EMF filters for power and control, drives are wired 3 phase.

  14. #14
    Join Date
    Jan 2005
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    15362

    Re: Dmm fault issue

    Quote Originally Posted by repauli1 View Post
    I have a large router, fighting issues with overcurrent faults when cycling power.
    On a cold start it always starts up fine, but if I cycle power to drives, when Oak and drives come back up, usally 1 or 2 drives fault out. If I power down, let it sit for 30min or so, start up, let it sit for 15minutes then it seems to start up.
    I am using a phase converter, and yesterday I switched power to a different phase converter.. same issue. Any clues?
    Ps: control voltage comes on with power up before oak boots, I do have a 30amp line reactor,individual EMF filters for power and control, drives are wired 3 phase.
    The RPC is the problem, do you need 3Phase these Drives run on 240v Single Phase just as well
    Mactec54

  15. #15
    Join Date
    Mar 2013
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    66
    Quote Originally Posted by mactec54 View Post
    The RPC is the problem, do you need 3Phase these Drives run on 240v Single Phase just as well
    Smdh, that worked..well over 40hrs messing with it.
    Thanks!

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