6MB Problems (Mazak Microcenter V)

[ma85562]

Hey folks,

I recently purchased a 1981 Mazak Microcenter V, and during the initial shakedown ran into some issues. While trying to move the head (w axis) up and down using the front panel switch (which wasn't working, BTW) , something happened and all hydraulics and other mechanical items stopped functioning. The control itself still functioned properly, just none of the hardware. I can still manually activate the individual contactors for the various systems, but the mechanicals won't "latch" at startup, almost like one of the e-stops were on. Diagnostic 701 actually said that an e-stop condition is in effect. On startup, the control simply did the bubble check, and went straight to the "not ready" screen. All other screens could still be accessed normally.

AS IF THAT WASN'T BAD ENOUGH...

While doing some very basic troubleshooting re: the above problem, I accidentally shorted the +5v block to the 0v block on the power supply when my probe slipped. The control shut down like it was supposed to, so I cycled the main power switch, pressed the "on" button on the ops panel, and waited. My heart sank when it went directly from the bubble check screen to a sad-looking screen stating "system error 901". +5v and +24v are still good, but now the third (from left) green LED in the middle of the motherboard is on, when I don't remember it being this way before... and I have no idea what it's meaning is anyway. My yellow Fanuc operators manual says that a 901 alarm is a BMU error (sorry, I can't remember which one at the moment). I am extremely sad that I might have damaged the BMU.

If anyone can offer some insight into either/both issue(s) I would be eternally grateful. I know the first problem is likely not actually a controller malf, but there are alot of bigbrains here, so who knows?

AND, if anybody is able to make available to me a Mazak Microcenter wiring diagram, I would be perpetually indebted... My 26-year-old machine seems to have had a fair number of "quick fixes" performed on it and I would like some OEM info to steer me straight.

Many thanks in advance,
Michael

[Dan Fritz]

The bubble memory alarm (901) might clear up if you try the bubble memory initialization procedure. Try this:

Note: this procedure will likely erase all your parameters, part programs, tool offsets, and PC parameters. I sure hope you have these recorded somewhere. If not, maybe another forum member with the same machine has them recorded and can e-mail you some files.

1) With the power off, remove the bubble memory board and look for a sticker that gives a bunch of 3-digit numbers. These are "Defective loop" numbers for that board's bubble device. Depending on how big of a memory you have, you may have anywhere from 1 to 4 separate bubble devices, so there may be more than one set of numbers. Write down all the numbers for device 1, device 2, etc. and reinstall the board.

2) Hold the minus (-) and the decimal (.) point button while you turn the power on. That should pop up an "IL" mode screen with 6 choices

3) Press "4" for "Bubble", then "2" for "Write by manual". You will get a message "Make BMU switch on".

4) On the main "master" board, look for a toggle switch labeled "BMU Free mode" and turn it on.

5) You should then be able to enter the 3-digit numbers for "device 1", pressing INPUT each time. When all the numbers for device 1 are entered, press the START key to write those numbers to the device. If you have more than one bubble device, you will then be able to enter the numbers for each device in turn. Each time you press START, there may be a several second delay while the control writes to the bubble device

6) If any alarms happen while performing this procedure, press RESET and you can start over. After all the defective loop data is entered, you will have to power down, power back up again, then you'll have to reload all your bubble data (Parameters, tool offsets, part programs, PC parameters, etc.)

If the BMU initializes OK, that will at least get you past the "901" alarm condition. Be sure to turn off that BMU free mode switch!

Now, for the W axis E-stop:
Each axis will have a pair of limit switches that will put the control into E-stop if the control were to run past the normal overtravel alarm switches. These are extra "Safety" switches to prevent the servo from damaging the ballscrew if the servo should go nutty and run away. Look for a loose wire to one of these switches, or look for a broken wire inside a cable duct. The fact that this alarm happened while you were moving the W axis tells me that one of these switches is actuated, filled with coolent, or that you maybe have a broken or loose wire. The E-stop circuit in the system 6 is one long "chain" circuit, with a lot of things in the chain. All the axes have safety overtravel switches, and you probably have other switches or relays that can put the control into E-stop (besides the big red button). ANY ONE of those things break the +24v E-stop chain and will shut down the servos. On many machines, it turns off the hydraulics as well.

You can take a voltmeter and check for +24v at every safety switch. You should see +24v on both sides of the switch if the switch is closed. If you see nothing on either side, then the chain is broken "upstream" somewhere. Finding out what all the things are in the chain (and in what order) would require the schematics for your machine from Mazak.

Good luck!

[ma85562]

Dan,

Thanks for your reply; I have seen your other Fanuc 6-series posts and was hoping that you'd be the one to respond.

I don't really like the idea of a complete bubble format, because I don't have a copy of the machine or PC parameters. This is sad, indeed. I suppose I will need to canvass other owners for parameter lists. There are still a few Microcenters around, so maybe I'll get lucky.

Regarding the e-stop condition: The w-axis didn't even move when I used the up-down switch on the front panel. I could hear what I think was the motor brake releasing, but there was no axis movement. It was only after I held the switch on for maybe five seconds that everything shut down, like in an overload condition. The axis moves fine when manually pushing the contactor button. The w-axis is just a plain old acme screw (driven through a worm up top) on this unit; it's only used to rough position the head. The various limit switches were nowhere near the dogs, but perhaps the switches are no good as you have suggested.

I thank you for your help!! I'll try to find some fellow Microcenter owners who would be willing to help me out with parameter lists. Maybe I'll fire off an e-mail to Mazak to see what documentation they have for me as well. I hope it's not too dear, as my machine is basically for hobbies and I don't want to spend a fortune on support docs...

Cheers,
Michael