Diagnosis and analysis of common faults in CNC machine tools - News - Global IC Trade Starts Here.

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First, find out the fault phenomenon

When the numerical control equipment fails, first understand the fault phenomenon, understand the situation of the first fault, and observe the process of the fault when possible, and observe under what circumstances the fault occurs. How does it happen? What caused the consequences. Only by understanding the first-hand situation will it be beneficial to eliminate the fault and clear the fault process, and the problem will be solved halfway. After clearing the fault phenomenon, and then according to the working principle of the machine tool and the numerical control system, the problem can be quickly diagnosed and the fault can be eliminated, so that the equipment can be restored to normal use.

Now the self-diagnosis capability of the CNC system is getting stronger and stronger, most of the faulty CNC systems of the equipment can be diagnosed, and corresponding measures, such as shutdown, can be used to generate an alarm display. When the numerical control device fails, sometimes an alarm message is displayed on the display, and sometimes there is an alarm indication on the numerical control device, the plc device, and the driving device. At this time, the alarm information should be analyzed according to the manual. Some alarms can directly confirm the cause of the fault. As long as the contents of the alarm information are clarified, the fault of the numerical control device can be eliminated.

The alarm information of other faults does not reflect the root cause of the fault, but reflects the result of the fault or other problems caused by it. At this time, careful analysis and inspection are required to determine the cause of the fault.

Second, to use the PLC status display function of the CNC system

Many CNC systems have PLC status display functions, such as PCSTATUS under the PC menu of Siemens 3 system, PLCSTATUS function under the DIAGNOSIS menu of Siemens 810 system, and PMC status display function of DGNOSPARAM function of FANUC 0T system, which can be displayed by these functions. The immediate status and contents of the PLC's inputs, outputs, timers, counters, etc. According to the working principle of the machine tool and the electrical schematic diagram provided by the machine tool manufacturer, some faults can be diagnosed by monitoring the corresponding state.

Third, we must use the PLC ladder diagram provided by the machine tool manufacturer

Most of the faults that occur in CNC equipment are checked by the PLC device. The mechanism of PLC fault detection is to run the PLC ladder diagram (ie program) programmed by the machine tool builder for a specific machine tool, and make logic judgment according to various input and output states. If a problem is found, an alarm is generated and an alarm message is generated on the display. Therefore, for some PLCs to generate alarm faults, or some faults without alarms, you can diagnose the faults by analyzing the ladder diagram of the PLC, and use the ladder diagram display function of the NC system or the off-machine programmer to track the operation of the ladder diagram online. Diagnose the speed and accuracy of the fault.

The above method is very effective for detecting the machine side faults, because these faults are nothing more than detection of switches, relays, solenoid valve damage or mechanical execution structure problems, these problems can basically be based on the PLC program, by detecting their corresponding state Confirm the point of failure. In the case of some system failures, sometimes the situation is more complicated. The following methods and detection principles can be used to quickly confirm the fault point.

For some faults involving the control system, it is sometimes not easy to confirm which part has a problem. To ensure that there is no further damage, replacing the suspected control panel with the standby control board is an effective way to accurately locate the fault point. Sometimes the control panel interchange with the same type of control system on other machine tools will diagnose the fault more quickly (in this case, it will ensure that the good board will not be damaged).

Check the fault should be based on the principle of internal and external, first mechanical and electrical, first simple and complex, first static and then dynamic, first public, special, first check the software and then check the hardware. For more complex faults in CNC equipment, especially when it comes to control systems, applying these principles simplifies the fault diagnosis process and avoids detours.