How to solve the problem of secondary damage in th

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How to solve the problem of secondary damage in the maintenance of CNC machine tools

this paper expounds the concept of secondary damage in the maintenance of CNC machine tools, analyzes the types of secondary damage, the main causes and hazards, and puts forward the maintenance methods to prevent the secondary damage of CNC machine tools

I. Introduction

with the rapid economic development, especially the recovery of machinery manufacturing industry, the number of CNC machine tools is increasing, and its maintenance has become a hot spot for users. However, the CNC machine tools produced in the early stage have reached their service life, and the CNC system is aging. Many early CNC systems are no longer produced, and the maintenance of machine tools has become ten difficulties. CNC machine tools involve mechanical, electrical, hydraulic, pneumatic, optical, computer technology and other fields of knowledge, especially the maintenance of CNC machine tools involves fault diagnosis, condition monitoring, digital testing and other related technologies. Therefore, its maintenance is very different from ordinary equipment in theory, method and means. Moreover, the users of CNC machine tools are diverse, and they lack a certain understanding of the working conditions and maintenance of machine tools, which makes machine tools frequent failures in the process of use

due to the lack of CNC equipment maintenance professionals in the enterprise, the existing maintenance personnel do not understand the professional knowledge enough. When carrying out maintenance operations on the machine tool, the software and hardware settings of the machine tool are changed or inappropriate operation methods are adopted, resulting in improper matching between the modules of the machine tool and even damage to the hardware equipment, causing secondary damage to the CNC machine tool

types of secondary damage

secondary damage is mainly divided into machine tool parameter damage, circuit board jumper or knob position damage, circuit board physical damage and other forms of damage

machine tool parameter damage refers to the artificial modification of the factory parameters of the CNC system, which makes the machine tool unable to work normally. For Siemens 810 CNC system, there are hundreds of setting data, mainly including general machine tool data, servo feed axis data, spindle data and machine tool data bits. Changing any of these data will affect the working state of the machine tool

machine tool parameter damage often occurs in the maintenance process, and the change of machine tool data is easy to be forgotten by maintenance personnel. When this repair fails, it will bring great trouble to subsequent maintenance. The maintenance of such damage is relatively simple. After finding out the cause, reset the data to restore the system

the CNC system is composed of independent functional modules, and there are many switches, jumpers and knobs on each module to meet different functional requirements. For example, there is a knob in the servo drive board to adjust the open-loop gain and zero drift of the system. When the function of such a knob is unknown, adjusting the position of any knob will damage the CNC system. Moreover, such damage is not easy to find and will cause obstacles to subsequent maintenance

physical damage of circuit board mainly refers to the phenomenon of artificial damage to electronic devices and circuit board fracture in the component level maintenance of circuit board

modern numerical control systems are composed of large-scale integrated circuits. During maintenance, integrated circuits are very sensitive to the release of high-voltage static electricity. Various synthetic fiber materials such as rubber soles, artificial floors, carpets, etc. will generate thousands of volts of static electricity on the human body, which will cause damage to CMOS devices or loss of CMOS RAM data. It has ultra light weight, super elasticity The advantages of good flame retardancy and other properties that can become an ideal choice for various uses even cause the wires of printed circuit boards to burn. In addition, due to the needs of large-scale integrated circuits, the circuit boards of CNC systems are often made into four or even higher layers of circuit boards. Frequent installation and adjustment of circuit boards when using replacement method for maintenance will bend the circuit boards and cause the inner wires to break. The maintenance of this kind of fault often requires professional testing equipment to complete, which increases the difficulty of maintenance

in addition, other forms of secondary damage, such as loose wiring, solder joints, component installation dislocation, should also be very vigilant in the maintenance of CNC machine tools

secondary damage real-time display the severity of the water volume curve

the consequences of secondary damage are often very serious, difficult to troubleshoot, long cycle and heavy workload

for example, in the late 1980s, China spent a lot of money in batches to introduce many Italian Mandelli pentahedral machining centers. The CNC system, which was independently developed by Mandelli in the early stage and centered on industrial minicomputers, is no longer produced. When the system runs abnormally, there is often no better solution. For example, after the CNC system of this type of machine tool in an enterprise is started, the screen is blank, but other parts such as the relay cabinet can be started normally after being powered on. When operating the system keyboard and the machine tool control panel, the machine tool has no reaction. After asking the maintenance personnel of the enterprise, we learned that the machine tool has been repaired many times by the enterprise's own maintenance personnel and other enterprise maintenance personnel, and the problem still exists. After the author's comprehensive inspection, it was found that the system power supply was faulty. After replacing the components of the power circuit board, the power supply was normal, but the system still could not start normally. Due to the lack of complete data, the hardware structure of the host of the CNC system had to be dissected and checked. It was found that the output end of the daisy chain interrupt system of the host was shorted. Combined with the hardware characteristics of small computers, the characteristics of computer interrupt working mode and the characteristics of CNC machine tools after startup, it is preliminarily judged that the short circuit is "artificially" short circuited. Restore the correct jumper position, and resume normal operation after the system is restarted. The problem is eliminated

the CK6150 CNC lathe used by an enterprise broke the safety tube circlip on a circuit board of the CNC system, and the mechanical vibration during the operation of the machine tool caused poor contact of the safety tube. The machine tool stopped intermittently, damaging the processed workpiece. The machine tool has been repaired for many times, but the fault has not been eliminated. Repeated maintenance made the wiring of the control system disordered, the external PLC program was lost, the servo system was damaged, and the secondary damage was serious. After replacing the servo system, re programming the PLC program and wiring, and replacing the fuse device, the system returned to normal. However, the workload of maintenance is greatly increased, and the maintenance lasts for a long time, which also has a certain negative impact on the production of enterprises

IV. prevention of secondary damage

the main method to prevent secondary damage in the maintenance of CNC machine tools is to divide the maintenance level reasonably. For example, the maintenance of numerical control machine tools is divided into mechanical structure maintenance, peripheral equipment maintenance of numerical control system, module level maintenance of numerical control system and component level maintenance of circuit board of photochromic material system successfully developed from known compounds, and the scope of relevant maintenance personnel is formulated. For example, such things have gradually evolved from the original viewing function to the current application field. The maintenance of peripheral equipment is limited to the operation of auxiliary parts such as limit switches, buttons, sensors, connecting cables and connectors. In addition, regular preventive maintenance of various maintenance levels is also an effective means to prevent CNC machine tool failures

as for the specific maintenance process, the maintenance personnel should strictly follow the maintenance regulations. Proper maintenance tools, maintenance sites and clothing should be selected to prevent all kinds of damage caused by static electricity and tools. During the maintenance process, attention should be paid to making maintenance records, recording various switch conditions, jumper conditions, etc. before maintenance. Once the maintenance fails, the original system state should be restored as far as possible. Take full charge of the working principle and device characteristics of the object to be repaired, and draw relevant drawings. During the maintenance process, the wiring should be standardized, and after the maintenance, detailed description materials should be prepared, archived and properly kept

v. summary

with the deepening of China's industrialization and the improvement of production specialization, enterprises can no longer maintain and repair equipment at the level of large and comprehensive maintenance personnel. The focus of production enterprises is mainly on the production and sales of products. Therefore, manufacturing enterprises should strengthen the joint maintenance of CNC equipment with professional CNC equipment maintenance enterprises or universities and scientific research institutes, which is very beneficial to the production and development of enterprises

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