DM2800 5 amp breaker tripping

[mp-]

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-

[mp-]

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.

mp-

[Caprirs]

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?

[mp-]

Originally Posted by Caprirs 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?

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[Caprirs]

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.

[mp-]

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-

[mp-]

No change with the new spindle amp.

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.

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[Al_The_Man]

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.

[mp-]

Originally Posted by Al_The_Man 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.

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[mp-]

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-

[mp-]

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.

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[Caprirs]

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.