[crobox]

I have spent quite a bit of time today with this frustrating machine.

I re-soldered some .016 wire into the "flag" fuses, thus repairing the three that had blown. So far they have not blown again. But this also did NOT clear up the ongoing problem. For good measure, I tested all the fuses for continuity, and all the "signal" third blades, for an open state. All good.

I discovered, sort of by accident, that manually pushing the overtravel limit switches for X and Y can SOMETIMES clear the servo overload alarm (but not for long; see below).

Today the machine was sort of randomly slipping in and out of a few different states.

In one state, the machine is in the servo overload (01) alarm state, and nothing seems to change that.

In another state, the servo overload alarm (01) state can sometimes be over-ridden with either the overtravel limit switch on X or Y, or sometimes with the Reset button on the pendant. Usually, this is as far as it gets, because the "not ready alarm" message continues to flash at the bottom of the screen, and nothing else is possible. Sometimes, however, both the overload alarm message AND the "not ready alarm" message will go away for a moment, and when that happens, after a time-lapse of about three seconds, the contactors on both the X and Z (but not Y) velocity control boards will "blip" closed for a second. During this second, one or more servo-motors sound like they are in a "stall." Then, the servo overload (01) alarm message comes back on, sometimes accompanied by the VRDY OFF (02) alarm message.

Once, today, I was holding the jog toggle switch for X while the contactors "blipped", and amazingly enough the X axis actually moved about 1.100" before the alarm messages came back on and the machine became frozen again. I have not been able to replicate that movement.

Also, the spindle now turns on and off.

It all seems really random to me.

Does all this mean anything to anyone?
Are there still qualified service personnel for a machine like this?
Should I start saving up for a new controller, or a new mill?

Thank you,
Christian

[WGoyer]

Christian,

I looks like at some point in the past the machine has been phased incorrectly. Now, if the spindle is running the correct direction, that problem is solved. Fanuc SCR drives dislike two things more than anything else:

1) Being run with reversed phasing (They blow fuses or sometimes scr's when phased incorrectly, even for a few seconds).
2) Being run on a phase converter.

I've been following this thread for awhile, but without re reading it all again, I'm not sure if you've mentioned if you have good three phase here or a phase converter.

This is a good control, and these are good drives. Parts are still out there.

Hang in there.

Warren
www.uptimecorp.com

[crobox]

Well, the machine was in fact phased incorrectly. I was confused by the fact that it currently has a reverse-helix end mill in it. Anyway, that is sorted out now.

But it didn't change anything.

And, it IS running on a phase converter. However, I have now tried it on two different phase converters, with identical results. Both phase converters put out voltages that vary across a pretty wide range.... I could spend a bunch of cash on a new one that puts out more even voltages, but I am very hesitant to do that without knowing that it will solve anything.

For now, I am out of ideas.

[WGoyer]

Christian,
Well, the phase converter is the culprit here. Your machine has SCR drives. SCRs, by nature need near perfect sine waves (like your utility would furnish) to operate properly. In your case, they need to be spaced 120 degrees apart, and they need to be either running at a 50 or 60 Hz. There is a jumper on the drive that selects this.
Phase converters work well for powering 3 phase induction motors and all kinds of inverter drives that are not very particular about the phase spacing. Even so, due to their imperfect output, an induction motor cannot be run at its full capacity. Usually, that is not an issue. Phase converters use the two legs of your 220V single phase (which are 180 degrees apart) and attempt to create a third phase spaced somewhere in between. Induction motors can function. Inverters that just use the 3 phase to pump up a capacitor bank could care less. SCRs care, A LOT!
There really isn't a good solution here, except to replace the SCR units with PWM type drives (such as those made by Advanced Motion, www.a-m-c.com) The old motors would work OK.
It might be good to just consider trading up to a newer machine that isn't phase sensitive.
Call me if you want to discuss it more. I've been through this many, many times.

Warren
www.uptimecorp.com

[Al_The_Man]

Even so, due to their imperfect output, an induction motor cannot be run at its full capacity. Usually, that is not an issue. Phase converters use the two legs of your 220V single phase (which are 180 degrees apart) and attempt to create a third phase spaced somewhere in between.

They are 180deg because you are only looking at single phase, when you introduce a 3 element, the reference point is shifted to create the 120deg phase angle between each.
This is a pic of home made RPC.
Al.

[crobox]

I'm slightly confused....

Al, are you saying that Warren is not correct in his thinking about the phase converter?

It IS true that I successfully powered up this exact mill using the exact same phase converter, when living in Los Angeles about seven years ago. So that does call Warren's theory into question.

It is also true, however, that the utility power I get here in rural northern New Mexico sucks insofar as it goes out pretty frequently, and is typically quite high (between 243 VAC and 258 VAC, more or less). For all I know, the power might suck in other more subtle ways, too.

If Warren is correct in his theory about the SCR drives not being able to tolerate the phase converter (possibly exacerbated by the crappy power), then that is significantly bad news for me. It's bad news because, while my cash-flow was pretty good back when I paid $6K for this mill back in LA seven years ago, my cash-flow is next to nothing now. I was hoping to get this mill running as a way to start generating a little cash. But I certainly can't imagine dumping this mill for a grand or two and paying upwards of $5K for a better one. I certainly won't get a tool changer on that budget!

Are there better phase converters that might work?
Are there power-conditioning transformers (or something like that) which might make the SCR drives happier?
What kind of costs are involved in swapping to PWM drives?
Another option, I suppose, is a new controller, but there's that whole cost issue again....

Thanks for your help everyone...
I very much appreciate it.
-Christian