1. Intuitive method: maintenance personnel carefully observe various parts of the system through the observation of various abnormal phenomena such as light, sound, and smell when the fault occurs, and narrow the fault range to a module or a printed circuit board.
Example 1: During the machining process of the CNC machine tool, there is a sudden shutdown. Open the CNC cabinet and check that the main circuit fuse of the Y-axis motor is burned out. After careful observation, check the components related to the Y-axis. Finally, it is found that the outer skin of the Y-axis motor power line is scratched by a hard object, and the damage touches the machine shell, causing Short-circuit blown fuse, after replacing the Y-axis motor power line, the fault is eliminated, and the machine tool returns to normal.
2. Self-diagnosis function method: The self-diagnosis function of the CNC system has become an important indicator to measure the performance characteristics of the CNC system. The self-diagnosis function of the CNC system monitors the working status of the CNC system at any time. Once an abnormal situation occurs, immediately display the alarm information on the CRT or use the light-emitting diode to indicate the approximate cause of the failure, which is the most effective method in maintenance.
Example 2: AX15Z CNC lathe, equipped with FANUC1 0TE-F system, fault display:
FS10TE 1399B
ROM TEST: END
RAM TEST:
The display of the CRT indicated that the ROM test passed and the RAM test failed. The failure of the RAM test is not necessarily a RAM failure. It may be that the parameters in the RAM are lost or the parameters of the battery are in poor contact. After inspection, the cause of the failure is that the battery is in poor contact after replacing the battery, so the above failure phenomenon occurs as soon as the power is turned on.
3. Function program test method: The function program test method is to compile the common functions and special functions of the CNC system into a function test program by manual programming or automatic programming, send it to the CNC system, and then let the CNC system run the test program , in order to check the accuracy and reliability of the machine tool to perform these functions, and then determine the possible cause of the failure.
Example 3: A CNC milling machine using the FANUC 6M system has a crawling phenomenon when the workpiece is processed in a curve. With the self-compiled function test program, the machine tool can run smoothly and complete various predetermined actions, indicating that the machine tool CNC system is working normally, so Check the curve processing program used, and found that the G61 command was used in programming, that is, each processing section must be checked once until it does not stop, so that the machine tool crawls, and the G61 command is changed to G64 (continuous cutting mode) command. After the replacement, the crawling phenomenon is eliminated.
Fourth, the exchange method: the so-called exchange method is to use spare printed circuit boards, templates, integrated circuit chips or components to replace the suspicious parts, so as to reduce the scope of the fault to printed circuit boards or chips. level one.
Example 4: The rotary table of the TH63 50 machining center rotates continuously after being lifted, without deceleration, and without any alarm signal. For this kind of failure, it may be caused by the failure of the simple position controller of the rotating workpiece table. In order to further confirm the fault location, it is considered that the simple position controller of the tool magazine of the machining center is basically the same as that of the turntable. Therefore, the exchange method is used for inspection. After the position controller of the tool magazine and the turntable is exchanged, the position controller of the tool magazine is reset according to the setting of the position controller of the turntable. After the exchange, the tool magazine rotates continuously, and The turntable operates normally, which confirms that the fault is indeed in the position controller of the turntable.
5. Principle analysis method: According to the composition principle of CNC, logically analyze the logic level and characteristic parameters of each point, analyze and judge from the working principle of each component of the system, and determine the maintenance method of the faulty part. The application of this method requires maintenance personnel to have a clear and deep understanding of the working principle of the entire system or each component, so that it is possible to locate the fault location.
Example 5: PNE710 CNC lathe has Y-axis feed out of control, whether it is jogging or program feeding, once the guide rail moves, it cannot stop until the emergency stop is pressed. According to the basic principle of the position control of the numerical control system, it can be determined that the fault lies in the position loop of the X axis, and it is likely that the position feedback signal is lost. In this way, once the numerical control device gives the command position of the feed amount, the actual position of the feedback is always If the position error is zero, the position error cannot be eliminated all the time, which leads to the loss of control of the machine tool feed. The pulse encoder of the position measuring device is removed for inspection, and it is found that the filament in the encoder is broken, resulting in no feedback input signal. After replacing the Y-axis encoder, the fault is eliminated.
6. Parameter inspection method: When the CNC system finds a fault, it should check the system parameters in time. The change of the system parameters will directly affect the performance of the machine tool, and even cause the machine tool to fail to work normally. If a fault occurs, the parameters are usually stored in the magnetic bubble memory or maintained by the battery. In the CMOSRAM, once the external interference or insufficient battery voltage will cause the system parameters to be lost or changed, causing confusion. By checking and correcting the parameters, the fault can be eliminated.
Example 6: G1 8CP4 CNC grinding machine, the CNC system is FANUC1 1M system, the failure phenomenon makes the machine tool unable to work, and the CRT display does not have any alarm information. Checking all parts of the machine tool, it is found that the CNC device and the connection units between the CNC and each interface are all good. Finally, the analysis is caused by the confusion of the stored data in the magnetic bubble memory caused by external interference. Therefore, the storage content of the magnetic bubble memory is completely After clearing and re-entering various parameters of the CNC system according to the manual, the CNC machine tool will return to normal. In addition to the several inspection methods described above, there are also measurement comparison method, percussion method, local heating method, voltage pulling method and open-loop detection method. Several methods are adopted and used flexibly to comprehensively analyze the fault and gradually narrow down the scope of the fault, so as to achieve the purpose of troubleshooting.