[Stpgagnon]

The Machine is a Niigata SPN50 with a 16-M Fanuc Control, and today the operator was running a piece that we do often. At is second piece, suddenly the Z axes crashed bruttaly in the piece. Like if he loose is position for a moment. Someone here told me that about 10 years ago, a problem like this happens and he think thats like if the program would have skip some lines and that causes the crash... Pretty strange. The program was not running in drip feed, and we recheck the program in the controller and everything is ok. The only error that we have is Z Excess (overload)... could it be the encoder? We redo the same program in slowmotion and everything was ok... All the position are good in the 5 Axes. The H1 for the tool was at the good dimension (before the crash)

So my question is, did someone here have an idea or have already a problem like this before? Or any suggestion. Is there is something i can try with the controller to test it?

As i said before, some guys here think that sometimes the controller skip some line in the programs? alerady see that?

We restart the machine after a mechanical check, and position check, etc... but i want to solve that problem.... We scrap a tool, a jig, and the vise on the block! And the operator began to be afraid of his machine.




I

[fuzzyracing1967]

First off I don't know that machine or control but have had some strange things like that happen.We have a old cinninati mill that will jump .100 up in y from time to time,(never realy crashed anything but has scaped a few parts along the way) what happens is the encoder reads a "tape" if you will and sometimes a chip will get on it and make it jump.Anouther machine we have (a comet vmc) will do something like that allso.I have done this once or twice if you stay up 2.000 to run through a program and at some point stop and take the tool down to the work surface to get quik look at somthing,( is the tool in the right place kind of thing) and you don't put it back in the same z postion it was in,and finish running through your program, what will happen when you go back to start the program to make a part it will think it is at .1 above the part but realy it is -2.00 . It's not pretty when this happens,but then again it helps keep the old reflexes working hitting that big red button .

[HuFlungDung]

I'd be scared of the machine too

Could it be due to something like a bad bit of memory? Suppose it somehow did not see "+" and went "-" or something? Maybe even something corrupting memory and perhaps it needs to be wiped somehow and start over? Don't ask me how.

[padobranac]

That happened to me too, on vetical mill with Fanuc 0M, Z axes with no reason falls down and hits table with tool, and alarm is "Z axis excess error", nothing more.

Could that be some problem with Z axis brake?

[Dan Fritz]

Crashes like this are very rare with Fanuc controls. If the program became corrupted in memory, you should be able to run that same program again and see it crash again. If you have a bit of bad memory, you should get a PARITY alarm, not a crash.

A servo drive problem can cause a crash if the servo can "run away". This is pretty rare also, because the machine should shut down the servos if the axis moves out of position on its own. It can happen, but it would require a failure of both the servo amplifier and the feedback device. If this is your problem, then just leaving the machine sit idle with the servos enabled might cause a runaway and a crash. No program operation is needed.

There are inputs from the operator's panel that can cause a crash. Do you have a "MLK" or "Machine Lock" button? If you do, then pressing it while the program is running will cause the coordinate system to "shift", maybe causing a crash. DON'T TOUCH THIS BUTTON unless you want to test-run the program without moving the machine. I know some people who cut the wires from the back of the MLK switch.

The DRN, or "Dry Run" button can cause all the feed moves to run at rapid, and will let you control all the feed overrides with the "Jog" override switch. By turning on DRN while the machine is running, you may start zipping around in rapid rather than moving at cutting feedrates.

Did the machine crash right away (at the begining of the program) or did it run the part OK up to the point of the crash? If it crashed right away, it could have been caused by a shifted coordinate system (and easy mistake) or a machine that has not been properly zeroed out before running the part. If the crash happened partway through the program, the coordinate system was probably established OK.

This is a very sensitive subject, but it must be mentioned: Is your operator well trained on this machine? Do all the crashes seem to happen on the same shift, or with the same operator? In my years as a field service engineer, I've seen problems that were the result of poor operator training, and I've also seen deliberate sabotage to avoid a particular job. We all hate to think that this kind of thing can happen, but it does sometimes, and we can't ignore the possibility.

[Mitsui Seiki]

The Machine is a Niigata SPN50 with a 16-M Fanuc Control, and today the operator was running a piece that we do often. At is second piece, suddenly the Z axes crashed bruttaly in the piece. Like if he loose is position for a moment. Someone here told me that about 10 years ago, a problem like this happens and he think thats like if the program would have skip some lines and that causes the crash... Pretty strange. The program was not running in drip feed, and we recheck the program in the controller and everything is ok. The only error that we have is Z Excess (overload)... could it be the encoder? We redo the same program in slowmotion and everything was ok... All the position are good in the 5 Axes. The H1 for the tool was at the good dimension (before the crash)

So my question is, did someone here have an idea or have already a problem like this before? Or any suggestion. Is there is something i can try with the controller to test it?

As i said before, some guys here think that sometimes the controller skip some line in the programs? alerady see that?

We restart the machine after a mechanical check, and position check, etc... but i want to solve that problem.... We scrap a tool, a jig, and the vise on the block! And the operator began to be afraid of his machine.




I

I had the same error in my Mitsui Seiki(Fanuc16M).
What happens is ,when you get this error(Ithink it's a 414 alarm)the machine axis loose it's brake power and instead of stopping when the alarm occurs it keeps going for a while.That's why it crashes.

The reason you get this error is because the Z axis is sluggish.Bad lubrication maybe.

[mwood3]

I am pretty sure this Z excess error fault is just a result of the interferance with the jig to the Z axis servo.

[Mitsui Seiki]

I am pretty sure this Z excess error fault is just a result of the interferance with the jig to the Z axis servo.

Could be,but the reason I got it on my machine was bad lubrication.