CNC machine tool is a very complex system which involves many application subjects. In addition, there are many kinds of CNC systems and machine tools, and their functions are different. It is impossible to find a general diagnosis method suitable for all CNC machine tools and all types of faults. Here we only introduce some common general methods. These methods are related to each other. In the actual fault diagnosis, these methods should be used comprehensively.
1. Self diagnosis function method although the modern CNC system has not reached a high degree of intelligence, it has a strong self diagnosis function. It can monitor the working condition of hardware and software of CNC system at any time. Once any abnormality is found, the alarm information will be displayed on CRT immediately or the general cause of the fault will be indicated by LED. Using the self diagnosis function, the state of the interface signal between the system and the host can also be displayed, so as to judge whether the fault occurs in the mechanical part or the CNC system part. This method is one of the most effective methods for maintenance work.
2. Functional program testing method The so-called function program testing method is to use manual or automatic programming method to compile a function test program for common and special functions of CNC system, such as linear positioning, arc interpolation, spiral cutting, fixed cycle, user macro program, etc., and input it into the CNC system, and then start the CNC system to run, so as to check the accuracy of the machine tool in performing these functions And then determine the possible causes of the failure. This method is a good way to judge whether it is a programming error or an operation error, or the cause of machine failure when the NC machine tool is idle for the first time when it is started up for a long time, and when the machine tool processing causes waste products but there is no alarm.
3. Isolation method is to disconnect some control loops, so as to narrow down the fault area. For example, in the jog mode of a machining center, the feed is stable, but the automatic is abnormal. First of all, it is necessary to determine whether it is the NC fault or the servo system fault. First, disconnect the servo speed given signal and use the battery voltage as the signal. If the fault remains, it means that the NC system has no problem. Further inspection shows that the y-axis clamping device is faulty.
4. After long-term operation, the components of the local temperature rising CNC system will be aged, and the performance will be worse. When they are not yet completely damaged, the faults that occur can become sporadic. At this time, a heat blower or an electric iron can be used to locally heat up the suspected components to accelerate their aging, so as to completely expose the faulty parts. Of course, when using this method, we must pay attention to the temperature parameters of components, and do not burn out the original good devices.
5. Knocking method when the fault of CNC system appears sometimes, it can be used to check the location of the fault. This is because the CNC system is composed of several printed circuit boards, each board has many solder joints, and the boards or modules are connected by connectors and wires. Therefore, any false welding or poor contact may cause failure. When the insulation is used to gently tap the suspected points with false soldering and poor contact, the fault will certainly repeat. If it occurs, the tapping point is likely to be the fault location.
6. In order to adjust and maintain the printed circuit board (PCB), a number of detection terminals are designed in the printed circuit board (PCB). The user can also use these terminals to compare the difference between a normal printed circuit board and a faulty printed circuit board. The voltage and waveform of these measuring terminals can be detected, and the cause and location of the fault can be analyzed. Even sometimes, it can artificially create "faults" for normal printed circuit boards, such as disconnection of wires or short circuits, removal of components, etc., so as to determine the cause of real faults. Therefore, the maintenance personnel should accumulate the correct waveform and voltage value of the key parts or easily broken parts of the printed circuit board under normal conditions. Because CNC system manufacturers often do not provide relevant information.
7. Using alarm number to diagnose fault is one of the main methods for fault diagnosis of CNC machine tools. If there is a fault in the machine tool and there is an alarm number displayed on the CRT, the corresponding analysis and diagnosis should be carried out according to the content of the alarm number. Maintenance personnel can analyze the phenomenon according to the alarm number, narrow the scope of inspection, and purposefully carry out a certain aspect of inspection. Alarm number (error code) generally includes the following aspects of fault (or error) information: (1) programming error or operation error; (2) memory work is not normal; (3) servo system fault; (4) programmable controller fault; (5) connection failure; (6) temperature, pressure, liquid level and other abnormal; (7) travel switch (or proximity switch) status is not correct. In addition to the above commonly used fault inspection and testing methods, there are also board pulling method, voltage deviation method, open-loop detection method and so on. Including the diagnosis methods mentioned above, all of these inspection methods have their own characteristics. According to different fault phenomena, several methods can be selected at the same time to flexibly apply and conduct comprehensive analysis on the fault, so as to gradually narrow the fault range and quickly remove the fault. Once the fault location is found, but there is no replaceable spare parts on hand, the transplantation borrowing method can be used as an emergency measure to solve the problem.
On 2018-08-08 11:45:46
