Common troubleshooting methods for CNC machine tools - Solutions - Huaqiang

Single chip microcomputer STM32L151CCU6

Brand AVX TPSE226M035R0125 Low impedance tantalum capacitor AVX 22

Electronic scale crystal oscillator 3.2*2.5mm 3225 16M (16.000MHZ) 12PF 10PPM 20PPM 30PPM

SMD aluminum electrolytic capacitor

L0504-Murata muRata common mode inductor 90Ω 150mA

Because the CNC machine tool fault is more complicated, and the CNC system self-diagnosis ability can not test all the components of the system, it is often an alarm number indicating a large number of fault causes, making it difficult for people to start. The following describes the troubleshooting methods commonly used by maintenance personnel in production practice.
1. Visual inspection method The visual inspection method is to observe the abnormality of various light, sound and taste when the fault occurs, and determine the fault range. The fault range can be reduced to a module or a circuit board, and then Exclude. Generally includes:
a. Inquiries: Ask the fault site personnel carefully the process of the fault, the fault image and the consequences of the fault;
b. Visual inspection: Overall check whether the working status of each part of the machine tool is in a normal state, whether there is any alarm indication for each electronic control device, partial inspection for burnout, component burnt, cracking, wire and cable falling off, and the position of each operating component is correct. Or not, etc.
c. Touch: Under the condition of power failure, you can touch the installation status of each main circuit board, the plugging status of each plug, the connection status of each power and signal wires, and touch and shake the components by hand, especially Large volume of resistive capacitance, semiconductor device with or without the sense of looseness, in order to detect some broken feet, virtual soldering, poor contact and other faults;
d. Power-on: Refers to the power-on analysis in order to check for smoke, fire, abnormal sound, odor, and presence or absence of overheating of the motor and components. If there is a catastrophic failure, it must be excluded before powering up.
Example: After a CNC machining center is running for a period of time, the CRT display suddenly shows no display failure, and the machine can continue to run. After the shutdown, it will be turned on again and everything will be normal. It has been observed that a fault can occur whenever vibration occurs during operation of the equipment. The initial judgment is that the components are in poor contact. When the display panel is inspected, the CRT display suddenly disappears. Check that two pins with one crystal are loose soldered. After re-welding, the fault is eliminated.
2. Initial reset method In general, due to system alarms caused by transient faults, hardware reset or power to the switch system can be used to clear the fault. If the working memory area of ​​the system is confusing due to power failure, plug-in circuit board or battery undervoltage, the system must be initialized and cleared. Before copying, pay attention to making data copy records. If the fault cannot be eliminated after initialization, perform hardware. diagnosis.
Example: When a CNC lathe is pressed, the microcomputer refuses to execute the machining program, and does not display the fault self-test prompt. The display screen is in the reset state (only the menu is displayed). Sometimes the manual and editing functions are normal, the user program is checked, and various parameters are completely correct. Sometimes, due to memory battery failure, battery replacement, etc., the system displays oversize or oversize in all directions (display size exceeds the machine tool) The maximum size that can be processed by the jin or exceeds the maximum size that the system can recognize. Remedy: Use the initial reset method to reset the system to zero (usually use a special combination or password).
3. The self-diagnosis CNC system has a strong self-diagnosis function and can monitor the working status of the hardware and software of the CNC system at any time. The self-diagnosis function can display the status of the interface information between the system and the host, thereby judging whether the fault occurs in the mechanical part or the numerical control part, and displays the general part of the fault (fault code).
a. Hardware alarm indication: refers to various status and fault indicators on various electrical devices including numerical control system and servo system. Combined with the indicator status and corresponding function description, the indication content and the cause of the failure and the elimination method can be obtained. ;
b. Software alarm indication: The system software, the plc program and the fault in the machining program usually have an alarm display. According to the displayed alarm number, the corresponding fault description and troubleshooting method can be obtained by comparing the corresponding diagnosis manual.
4. Function program test method The function program test method is to program the G, M, S, T, F functions of the numerical control system into a functional test program by programming method, and store them on the corresponding media, such as paper tape and tape. Run this program during troubleshooting to quickly determine the likely cause of the failure.
Functional program testing is often used in the following situations:
a. The machine tool processing causes waste and cannot be determined at the moment whether the programming operation is improper or the CNC system is faulty;
b. The numerical control system has a random failure. It is difficult to distinguish between external interference and system stability.
c. When the CNC machine tool with a long idle time is put into use or when the CNC machine tool is regularly inspected.
Example: A vertical milling machine of the FANUC9 system crawls when machining a curved part automatically, and the surface roughness is extremely poor. When running the test program, there is no crawling during linear and circular interpolation, thus determining the cause in programming. Careful inspection of the machining program revealed that the curve consisted of many small arcs, and the C61 command was used to check the correct positioning. The G61 in the program is canceled, and after the G64 is used, the crawling phenomenon is eliminated.
5. The spare parts replacement method replaces the bad circuit board with a good spare part. That is, in the case of analyzing the general cause of the failure, the maintenance personnel can replace the suspected part with the spare printed circuit board, integrated circuit chip or component. This reduces the fault range to the printed circuit board or chip level. And do the corresponding initialization start, so that the machine tool is quickly put into normal operation.
For the maintenance of modern CNC, more and more cases use this method for diagnosis, and then replace the damaged module with spare parts to make the system work normally. Do as much as possible to reduce the downtime. Use this method to ensure that the operation must be carried out in the power outage state. Also check the version, model, various marks, and jumpers of the circuit board. If they are not the same, they cannot be replaced. Marks and records should be made when the line is removed.
Generally, do not easily replace the CPU board, memory board and electric ground. Otherwise, the program and machine parameters may be lost, and the fault may be expanded.
Example: A CNC machine tool using Siemens SINUMERIK SYSTEM 3 system, its PLC Chuanchuan S5-130w/B, when a fault occurs, the R parameter input through the NC system PC function does not work during processing, can not be changed plus The value of the R parameter in the program. Through the analysis of the working principle and fault phenomenon of the NC system, it is considered that there is a problem with the motherboard of the PLC, and after being replaced with the motherboard of another machine tool, the problem of the PLC motherboard is further determined. After repair by professional manufacturers, the fault was eliminated.
6. Cross-transposition method When a faulty board or a faulty board is found and there is no spare part, the same or compatible two boards in the system can be interchanged, for example, two coordinate command boards or The exchange of the servo board determines the faulty board or the faulty part. This cross-transposition method should pay special attention to not only the correct exchange of hardware wiring, but also a series of corresponding parameters exchange, otherwise it will not only achieve the purpose, but will generate new faults and cause confusion, must be considered in advance. , design a good software and hardware exchange program, and then exchange and check accurately.
Example: A CNC lathe has a normal X-direction feed, and the Z-direction feed has vibration, noise, and precision. This is also the case when using manual and manual pulse feed. Observing the brightness of the indicator light of each driver board and its change is basically normal. It is suspected that the Z-axis stepping motor and its lead open circuit or Z-axis mechanical failure.换 Change the Z-axis motor lead to the X-axis motor, the X-axis motor runs normally, indicating that the Z-axis motor lead is normal; and the X-axis motor lead is changed to the Z-axis motor, the fault remains; it can be concluded that the Z-axis motor is faulty or Z-axis mechanical failure. The motor leads were measured and an open phase was found. Repair stepper motor, troubleshooting.
7. Parameter check method The system parameter is the basis for determining the function of the system. If the parameter is set incorrectly, it may cause the system to malfunction or a function is invalid. When a fault occurs, the system parameters should be checked in time. The parameters are usually stored in the bubble memory or stored in the CMOS RAM to be held by the battery. Once the battery is low or due to external interference, the individual parameters are lost or changed, and confusion occurs. Make the machine not working properly. At this point, the fault can be eliminated by checking and correcting the parameters.
Example: A CNC milling machine uses a measuring cycle system. This function requires a background memory. This function cannot be realized during debugging. The check found that the data bit existing in the background memory was not set, and the function was normal after being set.
Another example: a CNC lathe CNC tool holder has a sudden failure, the system can not automatically run, in the manual tool change, it will take a while to change the knife again.遂 Check the parameters such as the tool compensation, and find that the parameter P20 that is not described in the manual becomes 20, and the relevant data P20 is the tool change time parameter of the tool holder, which is cleared and the fault is eliminated.
Sometimes due to user program and parameter errors can also cause downtime, you can use the system's program self-diagnosis function to check and correct all errors to ensure its normal operation.
8. Measurement comparison method
When designing printed circuit boards, CNC system manufacturers designed some test terminals on the printed circuit board for adjustment and maintenance. The maintenance personnel can check whether the working state of the circuit is normal by measuring the voltage or waveform of these detection terminals. However, before using the test terminals for measurement, you should be familiar with the function of these test terminals and the circuit or logic relationship of the relevant parts.
9. Knocking method When the system failure is manifested as sometimes normal and sometimes abnormal, it can be basically determined that the component is in poor contact or the solder joint is open. When using the tapping method, when hitting the faulty part of the virtual welding or poor contact When the fault occurs.
10. After the long-term operation of the local temperature-increasing numerical control system, the components are all aging and the performance is deteriorated. When they are not completely damaged, the failure will sometimes be absent. At this time, the suspected component is locally heated by a soldering iron or a hair dryer, which causes a rapid failure. When operating, pay attention to the temperature parameters of the components, etc., be careful not to damage the good components.
11. Principle analysis method According to the composition principle of the numerical control system, the logic level and characteristic parameters of each point, such as voltage value and waveform, can be logically analyzed, and the instrumentation is used for measurement, analysis and comparison to determine the fault location.
In addition to the above commonly used fault detection methods, the plug-in board method, the voltage pull-off method, the open-loop detection method, and the like can also be used. In short, according to different fault phenomena, several methods can be selected at the same time for flexible application and comprehensive analysis, in order to gradually narrow down the fault range and eliminate faults faster.