How to quickly and accurately diagnose CNC equipment failures - Solutions - Huaqiang

Photocoupler

1. Observation

This is the most basic method. Maintenance personnel carefully observe various parts of the system, such as light, noise, sparks, smell, etc., to carefully view various parts of the system, and reduce the fault range to a printed circuit board or a module.

Example: A sudden shutdown occurs during the machining of a CNC machine. Open the CNC cabinet and check that the main circuit of the Y-axis motor is burnt out. After checking the components related to the Y-axis, it is found that the power line of the Y-axis motor is worn out, and it is placed on the bed, causing a short circuit. After the power line is replaced, the fault is eliminated. The machine tool returned to normal.

2. Parameter check

When the CNC equipment fails, check the parameter table for changes in time. System parameters are a guarantee of machine operation. They are stored in the bubble memory or CMOS RAM. Once the battery is insufficient or due to external interference, the individual parameters will be lost or changed, and the machine will not work properly. By checking, the parameters can be corrected to eliminate the fault.

Example: CK300 CNC machine tool, using FANUC OTC system, each part can not work, CRT does not have any alarm information. Check all parts of the machine and find that the connection system of the system and system and each interface is good. The analysis is caused by the external data causing the data stored in the bubble memory. Therefore, the storage contents are completely cleared and then re-entered. Parameters, the machine returns to normal.

3. CNC system self-diagnosis function The self-diagnosis function of the CNC system is an important indicator of its performance. It can display fault alarm information on the CRT or use diodes to indicate the general cause of the fault.

Example: AX15Z CNC machine tool configuration FANUC TOTEF system display

FS10TE 1399B

ROM TEST: ENO

RAM TEST:

This indicates that the ROM test passed and the RAM test failed. The RAM test failed, not necessarily the RAM failure. It may be that the parameters in the RAM are lost or the battery is not in good contact. The cause of the fault is that the newly replaced battery is defective, so it will malfunction when it is turned on.

4. Principle analysis

According to the composition principle of the numerical control system, the logic level and characteristic parameters of each point are logically analyzed, and the analysis and judgment are started from the working principle of each component of the system to determine the maintenance method. This requires the maintenance personnel to have a clear and deep understanding of the circuit principles of the entire system.

For example, the PNE710 CNC lathe has a Y-axis feed out of control. Whether it is jog or program feed, once it moves, it does not stop until it is stopped by an emergency. According to the basic principle of the position control of the numerical control system, it can be determined that the fault is on 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 zero, the position error can never be eliminated, and the machine feed is out of control. The position measuring device pulse encoder is removed for inspection and found in the encoder. The filament is broken, resulting in no feedback input signal. After replacing the Y-axis encoder, the fault is eliminated.

5. Functional program test

The function program test method is to program the functions of the numerical control system, such as linear positioning, circular interpolation, thread cutting, fixed cycle and other manual/automatic programming and methods into a functional test program, send it to the numerical control system, and then make it run. To check the accuracy and reliability of performing these functions, and to determine the cause of the failure.

Example: Using a CNC machine tool of FANUC6M system, the crawling phenomenon occurs when the workpiece is subjected to curve processing. With the self-programming function test program, the machine tool can smoothly run various predetermined actions, indicating that the machine tool and CNC system work normally, so The curve processing program used is checked. It is found that the 3661 command is used during programming, that is, the in-position stop check is performed once for each processing, so that the machine tool is crawled. After the G61 command is replaced with the G64 command, the crawling phenomenon is eliminated.

6. Spare plate replacement

In the case of analyzing the general cause of the failure, the spare printed circuit board, the template integrated circuit chip or the component is used to replace the suspected portion, thereby narrowing the fault range to the printed circuit board or chip level.

Example: The TH6350 center rotary table is rotated after lifting, and there is no deceleration, no alarm signal appears. This kind of failure may be caused by the failure of the simple position controller of the rotary table. In order to further confirm the fault location, considering that the simple controller of the tool magazine of the machining center is basically the same as the turntable, the exchange method is used for inspection. After exchanging the position controller of the tool magazine and the turntable, and resetting the magazine position controller according to the setting of the rotary table position controller, after the exchange, the tool magazine rotates, and the turntable runs normally, confirming the fault. It does come out on the position controller of the turntable.

In addition to the several inspection methods described above, there are other methods. During maintenance, the fault phenomenon should be used flexibly, comprehensive analysis, and the scope of the fault should be gradually reduced to achieve the purpose of troubleshooting.