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Troubleshooting and treatment methods for Fanuc CNC machine tool maintenance

Contributed by Xinyuehai 2019/12/27 9:19:38

0 Popularity: 1

  • Keywords: Fanuc CNC machine tool maintenance
  • Abstract: NC machine tool is a highly efficient automatic machine tool with a high level of integration of machine, electricity and instrument. It integrates new technological achievements in various fields such as computer technology, automation technology, servo drive, precision measurement and precision machinery. Is an emerging industrial control technology. Although different numerical control systems have differences in structure and performance, they have common features in fault diagnosis. Now let's talk about the general methods of fault analysis and maintenance of numerical control systems based on the actual work.

NC machine tool is a highly efficient automatic machine tool with a high level of integration of machine, electricity and instrument. It integrates new technological achievements in various fields such as computer technology, automation technology, servo drive, precision measurement and precision machinery. Emerging industrial control technology. Although different numerical control systems have differences in structure and performance, they have common features in fault diagnosis. Now let's talk about the general methods of fault analysis and maintenance of numerical control systems based on the actual work.

NC system fault repair is usually carried out in accordance with the three major steps: on-site fault diagnosis and analysis, fault measurement and repair troubleshooting, and system commissioning.

1

The following principles should be mastered in the fault diagnosis of CNC machine tools:

1.1 outside first then inside
The reliability of modern CNC systems is getting higher and higher, the failure rate of CNC systems themselves is getting lower and lower, and most of the failures are caused by non-system reasons. Since the CNC machine tool is a machine tool that integrates mechanical, hydraulic, and electrical functions, the occurrence of its failure will also be reflected by these three. Maintenance personnel should first carry out inspections one by one from the outside to the inside. Try to avoid unsealing and disassembling at will, otherwise the fault will be enlarged and the machine tool will lose accuracy and reduce performance. The failures outside the system are mainly caused by problems with detection switches, hydraulic components, pneumatic components, electrical actuators, and mechanical devices.
1.2 Mechanical and Electrical
In general, mechanical faults are easier to detect, but the diagnosis of CNC systems and electrical faults is more difficult. Before troubleshooting, first pay attention to remove mechanical failures.
1.3 Static first and then dynamic
Before the machine tool is in a static state, through understanding, observation, testing, and analysis, it can be confirmed that the fault will not be enlarged and an accident will occur after the power is turned on. In the running state, perform dynamic observation, inspection and testing to find faults. However, if a destructive failure occurs after power is applied, the danger must be eliminated before power can be applied.
1.4 Simple first then complicated
When multiple faults are intertwined with each other and there is no way to start, you should solve the easy problems first, and then solve the more difficult problems. Often, simple problems are solved, and difficult problems may become easy.

2

Fault diagnosis technology of CNC machine tools

NC system is a high-tech intensive product. To quickly and correctly pinpoint the cause and determine the location of its fault, it is necessary to use diagnostic technology. With the continuous development of microprocessors, diagnostic technology has also evolved from simple diagnosis to multi-functional advanced diagnosis or intelligence. CNC数控系统性能的一项重要指标。 The strength of the diagnostic capability is also an important index for evaluating the performance of the CNC system. The diagnostic technologies of various CNC systems currently used can be roughly divided into the following categories:
2.1 Startup diagnosis
CNC系统每次从通电开始,系统内部诊断程序就自动执行诊断。 Start-up diagnosis means that every time the CNC system starts from power-on, the system's internal diagnostic program will automatically perform the diagnosis. The diagnostic content is the most critical hardware and system control software in the system, such as CPU, memory, I / O and other unit modules, as well as MDI / CRT units, tape readers, floppy disk units and other devices or external equipment. Only after all items are confirmed to be correct is the entire system ready for normal operation. Otherwise, the fault information will be indicated on the CRT screen or light-emitting diode by an alarm. At this time, the startup diagnosis process cannot be ended, and the system cannot be put into operation.
2.2 Online diagnosis
CNC系统的内装程序,在系统处于正常运行状态时对CNC系统本身及CNC装置相连的各个伺服单元、伺服电机 、主轴伺服单元和主轴电动机以及外部设备等进行自动诊断、检查。 Online diagnosis refers to the built-in programs of the CNC system. When the system is in a normal operating state, each servo unit, servo motor , spindle servo unit, spindle motor, and external equipment connected to the CNC system itself and the CNC device are automatically diagnosed and checked. As long as the system is not powered off, online diagnostics will not stop.
0、1来显示其状态。 Online diagnostics generally include thousands of status displays for the self-diagnostic function, often using binary 0s and 1s to display their status. For positive logic, 0 indicates the off state and 1 indicates the on state. With the status display, you can determine the location of the fault. Commonly used interface status and internal status display, such as the use of I / O interface status display, combined with PLC ladder diagram and strong current control circuit diagram, using inference and exclusion methods can determine the true location of the fault point. Most of the fault messages appear in the form of alarm numbers. Generally it can be divided into the following categories: overheating alarms; system alarms; storage alarms; programming / settings; servos; travel switch alarms; connection failures between printed circuit boards.
2.3 offline diagnosis
Offline diagnosis is that when the index control system fails, the CNC system manufacturer or professional maintenance center uses special diagnostic software and test equipment to perform shutdown (or offline) inspection. Strive to locate the fault to the smallest possible extent, such as narrowing it down to a certain functional module, a certain part of the circuit, or even a certain chip or component, this fault localization is more accurate.
2.4 Modern Diagnostic Technology
IC和微机性价比的提高,近年来国外已将一些新的概念和方法成功地引用到诊断领域。 With the development of telecommunication technology, the cost-effectiveness of IC and microcomputer has improved. In recent years, some new concepts and methods have been successfully used in the field of diagnosis abroad.
1)通信诊断 ( 1) Communication diagnosis
CNC系统和专业维修中心的专用通讯诊断计算机通过连接进行测试诊断。 It is also called remote diagnosis, that is, the use of a telephone communication line to test and diagnose the faulty CNC system and the special communication diagnostic computer of a professional maintenance center. For example, Siemens uses this diagnostic function in CNC system diagnosis. The user connects the dedicated "communication interface" in the CNC system to the ordinary telephone line, and the dedicated data diagnosis computer in the maintenance centers of the two subsidiaries' data phones. It is also connected to the telephone line, and then the computer sends a diagnostic program to the CNC system, and the test data is returned to the computer for analysis and conclusion, and then the user is notified of the diagnostic conclusion and treatment.
The communication diagnostic system can also perform regular preventive diagnosis for users. Maintenance personnel do not need to visit the site. They only need to perform a series of operation inspections on the machine at a predetermined time. Analysis of diagnostic data in the maintenance center can find hidden faults so that they can be early. Take measures. CNC系统必须具备远程诊断接口及联网功能。 Of course, such CNC systems must have remote diagnostic interfaces and networking capabilities.
2)自修复系统 ( 2) Self-repair system
CNC系统的软件中装有自修复程序,当该软件在运行时一旦发现某个模块有故障时,系统一方面将故障信息显示在CRT上,同时自动寻找是否有备用模块,如有备用模块,则系统能自动使故障脱机,而接通备用模块使系统能较快地进入正常工作状态。 That is, a backup module is set in the system, and a self-repair program is installed in the software of the CNC system. When the software is found to be faulty when a module is running, the system displays the fault information on the CRT and automatically searches for it Whether there is a backup module. If there is a backup module, the system can automatically take the fault offline, and turning on the backup module enables the system to enter the normal working state relatively quickly. This solution is suitable for unattended automated workplaces.
It should be noted that in the actual use of the machine tool, there are also some failures that have neither alarms nor obvious phenomena. In this case, it is not easy to handle them. In addition, after this equipment fails, there is not only no alarm information, but also the lack of relevant information for maintenance. The diagnosis and treatment of this kind of failure must be carefully checked according to the specific situation, and the actual causes of the phenomenon shall be analyzed by analyzing the tiny points of the phenomenon. To find out the cause of this kind of failure, you must first find its real failure phenomenon from various surface phenomena, and then find out the cause of the failure from the confirmed failure phenomenon. A comprehensive analysis of a failure phenomenon is an important factor in determining whether it is correct. Before looking for the cause of the fault, you must first understand the following: Does the fault occur in normal work or just after the machine is turned on; Is the frequency of the occurrence of the fault the first time or has it occurred repeatedly? Confirm the correctness of the machining program; other people

3

Common troubleshooting methods for CNC machine tools

Because the failure of CNC machine tools is more complicated, and the self-diagnostic ability of the CNC system cannot test all the components of the system, an alarm number often indicates many failure causes, making it difficult for people to get started. The following describes the troubleshooting methods commonly used by maintenance personnel in production practice.

3.1 visual inspection method

The visual inspection method is that maintenance personnel determine the fault scope based on the observation of various abnormal phenomena such as light, sound, and taste when the fault occurs. The fault scope can be reduced to a module or a circuit board, and then eliminated. Generally includes:
A. Inquiry: Ask the staff at the fault site to inquire about the process, appearance and consequences of the fault;
B. Visual inspection: overall check whether the working status of each part of the machine tool is normal, whether there is an alarm indication for each electrical control device, partial inspection for insurance blowout, burnt components, cracks, and wires and cables falling off, and the position of each operating element is correct and many more;
C. Touch: When the machine is powered off, you can touch the installation status of each main circuit board, the connection status of each plug socket, the connection status of each power and signal wire, and touch and shake the components by hand, especially the large volume Resistance and capacitance, whether the semiconductor device feels loose, so you can check for some broken legs, false soldering, poor contact and other faults;
D. Power-on: In order to check for smoke, sparks, abnormal sounds, odors, and the presence of overheating motors and components when touched, power-on analysis will be performed immediately if found. If there is a destructive fault, it must be removed before applying power.
CRT显示器突然出现无显示故障,而机床还可继续运转。 Example: After running a CNC machining center for a period of time, the CRT monitor suddenly shows no display failure, and the machine tool can continue to run. After shutting down, everything is normal. Observation found that during the operation of the equipment, failure may occur whenever vibration occurs. The preliminary judgment is that the components are not in good contact. When checking the display board, the CRT display suddenly disappeared. Examination revealed that both pins of a crystal oscillator were loosely soldered. After re-soldering, the fault is eliminated.

3.2 Initial reset method

In general, the system alarm caused by a transient fault can be cleared by hardware reset or switching the system power on and off in turn. If the system's working storage area is chaotic due to power failure, plug-in circuit board, or battery undervoltage, the system must be initialized and cleared, and a data copy record should be made before clearing. If the failure cannot be ruled out after initialization, perform hardware diagnosis.
Example: When a CNC lathe presses the auto-run key, the microcomputer refuses to execute the processing 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, check the user program, and various parameters are completely correct; sometimes because the memory battery fails, replace the memory battery, etc., the system shows that the size in one direction is excessive or the dimensions in all directions are the most (the displayed size exceeds the actual machine The maximum size that can be machined can exceed the maximum size that the system can recognize). Remedy: Use the initialization reset method to reset the system to zero (usually use a special combination key or password).

3.3 Self-diagnostics

The CNC system already has a strong self-diagnostic function, and can monitor the working status of the hardware and software of the CNC system at any time. Using the self-diagnostic function, the status of the interface information between the system and the host can be displayed, so as to determine whether the failure occurred in the mechanical part or the numerical control part, and the general part of the failure (fault code) is displayed.

A. Hardware alarm indication: refers to the various status and fault indicators on various electrical devices, including numerical control systems and servo systems. Combining the status of the indicators and corresponding function descriptions can be used to learn the content of the instructions and the causes and troubleshooting methods;
B. Software alarm indication: The faults in the system software, PLC program and processing program are usually provided with alarm display. According to the displayed alarm number, you can learn the possible fault causes and troubleshooting methods by referring to the corresponding diagnostic instruction manual.

3.4 Functional program test method

G、M、S、T、F功能用编程法编成一个功能试验程序,并存储在相应的介质上,如纸带和磁带等。 The function program test method is to program the G, M, S, T, and F functions of the CNC system into a function test program and store it on the corresponding media, such as paper tape and magnetic tape. Run this program during fault diagnosis to quickly determine the possible cause of the fault.
The functional program test method is often used in the following situations:
A. Machine tool processing causes waste products and it is impossible to determine whether the programming operation is improper or the CNC system is faulty;
B. Random failure of the CNC system makes it difficult to distinguish between external interference and good system stability;
C. CNC machine tools that have been idle for a long time before being put into use or during regular maintenance of CNC machine tools.
FANUC9系统的立式铣床在自动加工某一曲线零件时出现爬行现象,表面粗糙度极差。 Example: A FANUC9 system's vertical milling machine has a creep phenomenon 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, so it is determined that the reason is in programming. After careful inspection of the machining program, it is found that the curve consists of many small arcs, and the C61 instruction was used to check the correct positioning outside the programming. After canceling G61 in the program and using G64, the creep phenomenon is eliminated.

3.5 spare parts replacement method

Replace bad circuit boards diagnosed with good spare parts, that is, in the case of analyzing the approximate cause of the failure, maintenance personnel can use spare printed circuit boards, integrated circuit chips or components to replace suspected parts, thereby narrowing the scope of failure Down to the printed circuit board or chip level. And do the corresponding initialization and start, so that the machine tool is quickly put into normal operation.
For modern CNC maintenance, more and more cases are diagnosed with this method, and then the damaged module is replaced with spare parts to make the system work normally. Minimize downtime as much as possible. When using this method, be sure to perform it in a power outage during operation. Also carefully check whether the version, model, various marks, and jumpers of the circuit board are the same. If they are not consistent, you cannot replace them. Mark and record when disconnecting.
CPU板、存储器板及电地,否则有可能造成程序和机床参数的丢失,使故障扩大。 Generally do not easily replace the CPU board, memory board, and electrical ground, otherwise the program and machine parameters may be lost and the fault may be enlarged.
SINUMERIKSYSTEM3系统的数控机床,其PLC采川S5—130W/B,一次发生故障时,通过NC系统PC功能输入的R参数,在加工中不起作用,不能更改加上程序中R参数的数值。 Example: A CNC machine tool using Siemens SINUMERIKSYSTEM3 system, its PLC adopts Sichuan S5-130W / B. When a failure occurs, the R parameter input through the PC function of the NC system does not work during processing and cannot be changed and added to the program. The value of the R parameter. Based on the analysis of the working principle and failure phenomenon of the NC system, it is considered that there is a problem with the main board of the PLC. After swapping with the main board of another machine tool, it is further determined that the problem is the main board of the PLC. Repaired by a professional manufacturer, the fault was eliminated.

3.6 Crossover

When a faulty board is found or one can determine whether it is a faulty board and there are no spare parts, the two boards in the system that are the same or compatible can be interchanged and checked, such as the exchange of two coordinate command boards or servo boards, from which Determine the fault board or fault location. This cross transposition method should pay special attention to not only the correct exchange of hardware wiring, but also a series of corresponding parameters. Otherwise, it will not only fail to achieve the purpose, but will also cause new failures and confusion of thinking. It must be considered in advance. , Design a good software and hardware exchange program, and then perform an exchange check without error.
X向进给正常,Z向进给出现振动、噪音大、精度差,采用手动和手摇脉冲进给时也如此。 Example: A CNC lathe has a normal X-feed, and a Z-feed has vibration, noise, and poor accuracy. This is also true when manual and manual pulse feeds are used. Observe that the brightness of the indicator lights of each drive board and their changes are basically normal. It is suspected that the Z-axis stepping motor and its lead wire are open or the Z-axis mechanical failure. Then change the Z-axis motor lead to the X-axis motor, the X-axis motor is operating normally, indicating that the Z-axis motor lead is normal; and then change the X-axis motor lead to the Z-axis motor, the fault remains; it can be concluded that the Z-axis motor is faulty or Z axis mechanical failure. Measure the motor leads and find that one phase is open. Repair stepper motor, troubleshooting.

3.7 Parameter check method

System parameters are the basis for determining system functions. Incorrect parameter setting may cause system failure or a function to be invalid. CMOSRAM中,一旦电池电量不足或由于外界的干扰等因素,使个别参数丢失或变化,发生混乱,使机床无法正常工作。 When a failure occurs, the system parameters should be checked in time. The parameters are generally stored in the magnetic bubble memory or in the CMOSRAM that needs to be maintained by the battery . Once the battery power is insufficient or due to external interference and other factors, individual parameters are lost or changed, resulting in confusion. The machine does not work properly. At this time, the fault can be eliminated by checking and correcting the parameters.

Article from: Machine Plus Little Zhuge

Review editor (Wang Jing)
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