PMC problem, the machine naturally does not work
In the Fanuc system, PMC is more like "the machine's brain logic layer”. Buttons can be pressed, emergency stop has not been triggered, the hydraulic station should be activated, the door is not closed can move the axis, these are not CNC interpolation in the pipe, but the PMC in a line by line judgment.
Therefore, the essence of 950 PMC System Alarm is not "a failure of an action”, but: PMC itself found that: now this logic state is not right, I can not go on. Once it can't, the safest thing to do is to shut down the system.
The most common cause of 950 alarms is actually in the I/O
We have dealt with many 950 alarms, and in the end, we found that the problem does not lie in the system board itself, but in the I/O Link or external signals. For example, the
I/O module suddenly loses power; the I/O Link wire is a little loose; the machine vibrates for a long time and the terminals are oxidized; or even an external module starts up a little slow.
PMC in the start or run, found that "the signal did not come” "inconsistent state”, will directly give you a 950. so you will see a typical phenomenon: some machine tools are 950 as soon as the machine is turned on, and some are running suddenly 950. So you see a typical phenomenon: some machines start up with a 950 and some run with a sudden 950.
Some situations are "data level” problems
There is another type of 950 that occurs after a sudden power outage, frequent power jumps, or UPS instability. The PMC's program and status data are supposed to be read and written in a relatively clean environment. Once the power is forcibly disconnected while writing data, the next time the power is turned on, the PMC realizes that the logical data does not match up, and again, the alarm will be raised directly.
In this case, you will find: there is no external abnormality in the machine, and the wires have not been moved, that is, as soon as the machine is powered up, it will be 950. At this time, those who have backed up the PMC are very comfortable; those who have not backed up will be very passive.
Main board or PMC hardware failure, but not so much
Many people see "System Alarm”, immediately suspect that the CNC main board, PMC board bad. But to be honest, the percentage of PMC hardware failure is not that high. Of course, the old machine, long-term high temperature, humid environment, PMC memory, logic circuit aging, may indeed lead to the repeated occurrence of 950.
It's just that this situation is usually characterized by one thing: how you deal with external signals, how to reboot, the alarm is unstable, or even more and more frequent. At this point, it doesn't make much sense to keep trying on the machine.
How do we usually determine the direction of the 950?
When assisting on-site or remotely, we usually start by asking a few questions: did the alarm go off right after powering on the machine, or during operation? Has the electrical cabinet, I/O, or external wiring been touched recently? Is there any abnormal power failure or power jump? When the alarm appears, is it accompanied by other I/O or system prompts?
These questions, not a set of words, but in order to determine: this is a "signal problem”, or "system problems. If the direction is right, the processing speed will be much faster.
About prevention, in fact, just a few small things
PMC alarms are seldom "sudden and unresolved”, but more of a long-term accumulation.
Stable power supply, clear wiring, regular checking of the status of I/O modules, and backup of PMCs and parameters are just some of the basic things that can minimize 950 alarms.
One last thing
Fanuc 950 PMC System Alarm is not the same as system scrapping. It tells you that the information received by the PMC is no longer a "state it can trust”. As long as you patiently follow the line of I/O → external signals → data → hardware, most 950s can be located and solved.
If you have checked the field wiring, signals, data, or repeated 950, then you need to take out the PMC or motherboard, in a controlled environment to do professional testing. songwei in the daily work, often help customers deal with Fanuc PMC alarms, system board testing and repair, to avoid endless trial and error in the machine tool, but also can significantly reduce downtime. If you have any problems in this area, please feel free to consult our
Songwei team.
