Discussion on the problem of secondary damage in the maintenance of CNC machine tools

I. Introduction

With the rapid development of the economy, especially the recovery of the machinery manufacturing industry, the number of CNC machine tools is increasing, and its maintenance and maintenance has become a hot spot for users, but the early production of CNC machine tools has reached the end of its life, the CNC system is aging, and many early CNC systems. It is no longer produced, and machine maintenance and repair becomes ten difficult. CNC machine tools involve mechanical, electrical, hydraulic, pneumatic, optical, computer technology and other fields of knowledge, especially CNC machine tool maintenance related to fault diagnosis, condition monitoring, digital testing and other related technologies, therefore, its maintenance in theory, method, means There is a big difference between them and ordinary equipment. Moreover, the users of CNC machine tools are diverse, and they lack a certain understanding of the maintenance and maintenance of machine tool working conditions, which makes the machine frequently fail during use.

Due to the lack of professional personnel in CNC equipment maintenance, there are insufficient knowledge of professional knowledge of existing maintenance personnel. When the maintenance operation of the machine tool is changed, the software and hardware settings of the machine tool are changed or improper operation methods are used, which makes the matching between the modules of the machine tool improper or even caused The hardware equipment is damaged, causing secondary damage to the CNC machine.

Second, the type of secondary damage

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

Machine tool parameter destruction is an artificial modification of the factory parameters of the index control system, so that the machine tool can not work normally. In the case of the Siemens 810 CNC system, there are hundreds of setting data, including general machine data, servo feed axis data, spindle data and machine data bits. Changing any of these data will have an impact on the working state of the machine.

Machine parameter destruction often occurs during maintenance, and changes in machine data are easily forgotten by maintenance personnel. When this repair fails, it will cause a lot of trouble for subsequent repairs. Maintenance of such damage is relatively simple. After identifying the cause, reset the data to restore the system.

The CNC system consists of independent functional modules, each with a number of switches, jumpers and knobs to suit different functional requirements. For example, there is a knob for adjusting the system open loop gain and zero drift in the servo drive board. In the case where such a knob is unknown, adjusting the position of any of the knobs will cause damage to the CNC system. Moreover, such damage is not easy to find and will cause obstacles to subsequent maintenance.

The physical damage of the circuit board mainly refers to the phenomenon of electronic device damage and circuit board breakage caused by human beings in the component level maintenance of the circuit board.

Modern CNC systems are composed of large-scale integrated circuits. The integrated circuits in maintenance are very sensitive to the release of high-voltage static electricity. Various synthetic chemical materials such as rubber soles, artificial flooring, carpets, etc. will generate several thousand volts of static electricity on the human body, which will cause Damage to CMOS devices or loss of CMOS RAM data can even cause printed circuit board traces to burn out. In addition, due to the needs of large-scale integrated circuits, the circuit boards of numerical control systems are often made into four or more layers of circuit boards. When the replacement method is used for maintenance, the circuit boards are frequently installed and adjusted, which will force the circuit board to bend. Causes the inner conductor to break. Maintenance of such faults often requires professional testing equipment to complete, and the difficulty of repair increases.

In addition, other forms of secondary damage such as poor wiring, solder joints, and component misalignment should be very vigilant in the maintenance of CNC machine tools.

Third, the severity of the second damage

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

For example, in the late 1980s, China introduced a number of Italian Mandelli pentahedron processing centers in batches. The CNC system was developed by Mandelli in the early stage of industrial small computers. It is no longer produced when the system is running. When it is not normal, there is often no better solution. For example, after the CNC system of this type of machine is started, the black screen, but the relay cabinet and other parts can be started normally after being powered. There is no reaction to the machine keyboard and the machine control panel. Inquired about the maintenance personnel of the enterprise that the machine tool has been repaired many times by the company's own maintenance personnel and other enterprise maintenance personnel. The problem still exists. After thorough investigation, I found that the system power supply is faulty. After replacing the power circuit board components, the power supply is normal, but the system still cannot start normally. Due to the lack of complete data, the hardware structure of the CNC system host was examined and found that the output of the host daisy chain interrupt system was shorted. Combined with the characteristics of the small computer hardware and the characteristics of the computer interrupted working mode and the characteristics of the CNC machine tool after booting, it is preliminarily judged that the short wiring is short-circuited by "man-made". Restore the correct jumper position, resume normal operation after the system restarts, and the problem is eliminated.

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