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IndustryArena Forum > MetalWorking Machines > Dyna Mechtronics > DM2800 5 amp breaker tripping
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  1. #1
    Join Date
    May 2005
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    39

    DM2800 5 amp breaker tripping

    I was happily machining away today when for no obvious reason the 5 amp
    breaker inside the cabinet tripped and the spindle and axes stopped (this
    breaker is located underneath the V Bus Pre-Regulator board).

    So, twice I reset everything, restarted the program, and about 4 minutes into
    the program trips.

    I think the V Bus Pre-Regulator is part of the spindle motor control
    electronics, but couldn't explain it's function. I checked the spindle
    (free turning) and confirmed the motor spins free with the belt off. And that's where my unguided diagnosing skills end.

    Any ideas?

    mp-

  2. #2
    Join Date
    May 2005
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    39
    Additional info:

    The machine seems to be low on spindle power. The spindle will bog noticeably (before breaker trips) running a reasonably small cutter: .19" dia, 3fl, Al specific cutter, 10K RPM, 36 ipm, .17 deep, full slot.

    I don't know what the hp requirement would be for that cut, but seems like a 1.25 hp spindle motor would handle that.

    Roberto at Dynamechtronics gave me some things to check, hopefully it's a simple problem.:drowning:

    mp-

  3. #3
    Join Date
    Oct 2005
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    672
    It may be possible the breaker is too sensitive from age? I have little experience with those machines but the three big power draws are the power supply for the boards, power supply for the axes and spindle amp.

    How often does it happen? Is it repeatable?

  4. #4
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    May 2005
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    39
    Quote Originally Posted by Caprirs View Post
    It may be possible the breaker is too sensitive from age? I have little experience with those machines but the three big power draws are the power supply for the boards, power supply for the axes and spindle amp.

    How often does it happen? Is it repeatable?
    Not sure on the breaker sensitivity, I could try to dream up some way to test it's trip current.

    The problem is definitely repeatable. Both the spindle and the axes stop together when the breaker trips, and it seems to happen faster when I'm running faster feeds/speeds (higher chip load).

    So there's one power supply for the spindle and axes, and one for the boards?

    mp-

  5. #5
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    Oct 2005
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    672
    There were (I think) two different spindle amps used over the years. One required an external power supply, the other used direct 220VAC wall power as I remember. It's been over a decade since I've seen one of those 2800s. There should be a power supply that provides 5VDC/12VDC/24VDC and another that provides 48V?

    If it is repeatable, try running the program in air, no cutting and see if the problem persists. If it still trips with no cutting load, run the program again in air with the spindle off. If the problem is with an axis, the breaker should trip even with no cutting load.

  6. #6
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    May 2005
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    39
    The problem is easy to duplicate, all I have to do is try to run a .188 endmill, .18 deep at 24 ipm in 6061. The spindle slows significantly as it goes into full slotting, gets maybe 10 inches then the breaker trips. Run the program without a tool and it runs straight through.

    I tried to stall the axes motors while running the program in air, putting much more resistance on the axes than a dinky .19 em, and the machine breaker did not trip. I think this indicates the current draw problem lies with the spindle control electronics.

    I believe you're right about the power supplies.

    The machine came with a couple spare spindle amps, and by the looks I think one is still new. I'm going to throw that at it and see what happens.

    Thanks,

    mp-

  7. #7
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    May 2005
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    39
    No change with the new spindle amp.(chair)

    According to my machining consultant program, this cut would require about .2 HP. Doesn't seem right that it wouldn't be able to take that cut without overloading the electrical.

    mp-

  8. #8
    Join Date
    Dec 2003
    Posts
    24216
    It seems to me a 5amp breaker would be too small for all but the very smallest of spindles, unless it feeds a power supply for example, although if it only trips when in a cut???
    Is it possible to trace what the breaker is Actually feeding?
    I assume this is a single phase machine? Otherwise I would have said you may have one phase out on an SCR drive?
    What type of spindle motor is it?
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  9. #9
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    May 2005
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    Quote Originally Posted by Al_The_Man View Post
    It seems to me a 5amp breaker would be too small for all but the very smallest of spindles, unless it feeds a power supply for example, although if it only trips when in a cut???
    Is it possible to trace what the breaker is Actually feeding?
    I assume this is a single phase machine? Otherwise I would have said you may have one phase out on an SCR drive?
    What type of spindle motor is it?
    Al.
    I think the breaker protects both the spindle amp, and the power supply for the stepper drivers, though I couldn't tell you how schematically.

    It is a single phase machine. The spindle motor is brushless DC.

    mp-

  10. #10
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    May 2005
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    New info- After another phone consultation with Roberto at Dyna, I ran a test where I observed the LED monitor lights on both the spindle amp and the V-bus pre-regulator board while rapidly turning the spindle speed down and up (under local control). The light on the spindle amp stayed green throughout, and the light on the V-bus board flickered on-off indicating it's (supposedly) working correctly.

    Current thought is that the motor magnets may be weak, causing a high current situation. Don't ask me the specifics on how that works..

    Motor repair (new motors not available) is $655 flat rate. Or, I can possibly adapt another type of motor/and drive, using newer technology.

    At the end of my last conversation Roberto suggested checking to see that the spindle encoder is clean. I'm not holding out hope on that one, though I have solved a hunting speed issue before by blowing out the dust... We'll see.

    mp-

  11. #11
    Join Date
    May 2005
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    39
    I confirmed that the current is exceeding the breaker capacity by checking current draw on power wire to the spindle amp.

    After searching a bit for alternative motors, I decided to go the most economical route which it to send the motor to Rockwell Automation for rebuild ($655). A company called SEM (UK) will custom build a motor to spec for $1750, but then I'd need to spend another $250 with Dynamechtronics to get a couple custom cables and to have them 'tune' the system.

    The worst part about this experience is having to wait 4-6 weeks for the motor rebuild.

    mp-

  12. #12
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    Oct 2005
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    672
    Glad you found the problem. Knowing what is wrong is a big step.

    For what it's worth, that sounds like a cheap fix. One of my DM4400M mills needs the servo amp repaired. Mitsubishi quoted me about $2100 not including shipping. Replacement with a refurbished unit was over $4K.

  13. #13
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    May 2005
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    Well, I (and Roberto) *think* the motor is the problem. I know little about servo motors and their controls, so I'm nervous pinning the problem on a part that 'works'. The motor would still start, spin up to set RPM, and stop as expected, just didn't have much power (and would trip the breaker). Maybe weak magnets, maybe the windings were shorting to each other under load, or who knows what else could go wrong with an otherwise simple electric motor.

    As for the price, you're right, I will be getting off easy by comparison to what some industrial components can cost. What's troubling is that this particular motor probably cost a couple hundred new, back in the day. In fact I found a very similar motor (not similar enough to use however) that sold new for $350 in 2005.

    Enough crying. Let the waiting begin.

    BTW, Caprirs, I really appreciate reading your posts regarding Dynamechtronics machines, the company, etc. Are you still in contact with anyone in the company (in San Jose)? I haven't seen any new products in years, the website hasn't been updated since forever. Any idea where the company is headed? Do they have so many older machines in the field that they can continue on the revenue generated by parts and service?

    mp-

  14. #14
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    Oct 2005
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    672
    I don't think Dyna knows they have a web site. It has not changed since I worked for them over a decade ago.

    Dyna is still doing decently internationally. They sell full size VMCs to South America and Asia. Machines are assembled in Taiwan and/or China then shipped directly to the customer. There are numerous models available not shown on the web site.

    I usually have some reason to call and talk with them a few times a year. There are about 5 people in the San Jose office.

  15. #15
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    May 2005
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    Motor back from Rockewell

    Rockwell did a great job getting the motor back to me, less than a week!

    Too bad the breaker still trips. I was afraid of this outcome. :tired:

    Not sure what to throw at it next. Perhaps some gasoline, and a match.

    mp-

  16. #16
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    Oct 2005
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    That's not good. I wish I could be more help but I am just not familiar with these machines.

    However, there are only a finite number of components. You have replaced the spindle amp and the spindle motor and get the same results. You have confirmed there is sufficient current going into the amp to trip the breaker.

    Is the spindle amp running off the incoming 220VAC? Or is there a separate power supply?

  17. #17
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    May 2005
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    Just for kicks, I swapped out a presumed good Dyna spindle amp interface board and no change.

    The machine is running off 110V, I'll have to check to see from where the amp is powered.

    Anyone care to look at a scan of the wiring diagram?

    mp-

  18. #18
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    May 2005
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    39
    I see power coming from the transformer, through the magnetic contactor, 5 amp circuit breaker, bridge rectifier, and then to the AMC amplifier.

    mp-
    Attached Thumbnails Attached Thumbnails backup of wiring diagram.jpg  
    Attached Files Attached Files

  19. #19
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    Oct 2005
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    Thanks for the schematic. That helps. Does the machine use 110VAC or 220VAC from the wall? I thought these were 220VAC machines?

    The incoming wall voltage goes through the bridge rectifier to convert it to DC. It goes to the VBUS regulator to get stepped up to (I think?) 160VDC. That 160VDC goes to the AMC amp to power the spindle motor. The two resistors shown coming off the VBUS regulator are for regenerative braking for the spindle motor. When the spindle is commanded to stop, the spindle motor is kind of switched to be a generator and the voltage/current is dumped across those resistors which helps slow the motor quicker.

    Since you've replaced the motor and tried a spare amp, the problem must be the bridge rectifier (converts the incoming AC to DC) or the VBUS regulator. I haven't a clue how to diagnose those. Sorry.

  20. #20
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    May 2005
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    These machines can run either 110V or 220V, I have this one running 110V from the wall.

    I replaced the Bridge Rectifier, no change. I'm not sure how the Vbus Regulator could be causing a current spike, but I'll call Dyna tomorrow to ask them about that.

    At one point I was advised to make sure the encoder is clean, which I did. I guess bad feedback can create unusual problems. I'm wondering if the encoder could be going flaky, or maybe I've got a bad cable...

    Rockwell (motor repair facility) does not give any information about what they test, or what they replace. As near as I can tell they replaced nothing on my motor (no 'new' looking parts). I hope they didn't miss the problem.

    mp-

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