CNC machine tools can adapt to the automatic processing of different parts. When changing the processing parts, you only need to change the NC program instead of the special process equipment such as the cam, the mold, the template, or the drill die. It has the features of high production efficiency, high processing precision and stable processing quality. Economical CNC machine tools are widely used in small and medium-sized enterprises due to their low investment, quick results and simple system structure. However, due to the limitations of CNC machine tools, especially the most economical CNC machine tools have been transformed from old CNC machine tools. The failure rate of this machine tool is also high during use. According to statistics, the faults of CNC lathes occurred in the electrical system (27.74%) turret or tool post (18.41%), CNC system (10.0%), chucks, fixtures and other machine tool accessories (10.02%), power supply (7.39%) , servo unit (6.35%) and other parts. Obviously, in the CNC machine tool components and subsystems, the most frequent fault is the machine tool electrical system. The typical failure analysis of the machine tool's electrical system during the use of the CNC machine is summarized as follows: 1 Typical failures and troubleshooting The lost or sudden stop of the Z-axis feed is equipped with a model of the BKC2-III type CNC system produced by Jinan. CNC machine tools, when processing parts, appear Z axis stepper motor occasional lost or sudden stop feed failure, so that the Z-axis stepper motor running, everything is normal. For this reason, the control panel was found to have no error information and no abnormal display in the Z-direction. Initially, it was determined that the mainboard had no problem. Check the Z-axis driving part, high-power tube, and the corresponding circuit of the interface board, and find that the Z-axis always fails when it is processed to a position close to the spindle box. Therefore, it may be estimated that a strong vibration occurs during the processing of the workpiece to make the Z-axis of the CNC system. Part of the link caused by poor contact. Carefully inspect the Z-axis control section and find that the root connection between the interface board and the driver board is a dummy weld. The failure disappears after re-welding. Sudden slowing of the feed rate in the X direction, abnormal display on the control panel is still a certain CNC machine equipped with a BKC2-III type CNC system manufactured by Jinan. In the process of use, “the feed rate suddenly slows down and the control panel displays Abnormal fault: Due to the abnormal display of the control panel, check the motherboard first, and find that the CPU of the system is a 280 chip, and all the integrated boards of the motherboard are provided with sockets, instead of being directly soldered on the printed board, so it may be judged that there may be poor contact of electrical components. Phenomenon, the CPU, EPROM, RAM chip re-plugged one by one, when the RAM chip is removed and re-inserted into the socket after the test machine, found that the failure disappeared.The machine data and processing program loss after shutdown phenomenon is equipped with a German TRAIN system HIDENHAIN TNC155 The imported Italian CNC milling machine, when used in winter in a certain year, the CNC system of the newly replaced battery often suffers from the loss of machine data and machining programs after shutting down: sometimes when the machine tool is being processed automatically, the program suddenly interrupts and the CNC system crashes. After the winter, the trouble disappeared naturally, and later it was winter or rainy. The barriers reappeared frequently, and sometimes the machine parameters were lost due to shutdown, and when the data was re-entered, the CNC system crashed.According to the occasional power-on operation, and the phenomenon of this failure phenomenon was less frequent in the summer, this may be due to The changes in temperature and humidity caused some poor connection of the connectors.We turned off all interference sources that could cause interference, and checked all the ground cables and external plugs for no problems. After the chassis was opened, the bus slot was found to be plugged in. Of the three circuit boards that were connected, one of them had been bent due to moisture, which caused the circuit of the printed circuit board to be broken or poorly connected.After the board was fixed and plugged in, the power test machine failed and the X axis stepping occurred. The motor suddenly stopped feeding, and the feedback signal was disorderly. In the production process, an economical CNC lathe that was transformed by the old ordinary lathe in a certain factory, the X-axis stepper motor suddenly stopped feeding, and the feedback signal of the control panel was disorderly. Turn off all interference sources that can cause interference and the failure of the retry machine has not been eliminated. A detailed examination of the "axis control part was found to be due to the transverse movement motor (X-axis stepping motor) mounted on the carriage. When the processing tool holder was removed from the workpiece, the guard plate was moved along with the carriage to expose the X-axis stepping motor. Come out and cause the cutting fluid to wet the motor and infiltrate into the cable plug. Dry and re-connect the cable, the test machine failure is eliminated. This is mainly because the Z-axis stepper motor has two cables. One is power supply and the other is signal feedback. When the cable enters the water, the feedback signal is disorderly and the system will reflect it, resulting in machine failure. 2 The prevention and maintenance of electrical systems refer to all electrical components except the CNC system and the power supply and their wiring connections, which are usually referred to as the strong parts. It includes buttons, switches, proximity switches, relays, solenoid valves, sensor elements, etc. It is scattered in various parts of the electric control cabinet and the machine body. In the production site where the machine tool is subject to high vibration, dust and heavy dust, and the climate is humid, electronic components, connecting lines, and fuses of the electrical system are prone to poor contact, damage to components, and broken fuses. This is the main reason for the frequent failure of the electrical system of CNC machine tools. Therefore, careful prevention and maintenance must be performed during use. In the production process, the waterproof (oil) and dustproof CNC machine tools are usually installed outside the processing area during the production process, but the execution components, detection components and related cables of the CNC system, such as servo motors, travel limit switches, The zero return switch and so on are close to the processing area, and the coolant should not be opened too much during processing, causing the coolant to splash wet and cause the machine to malfunction: usually the numerical control device of the numerical control machine tool adopts certain dust-proof measures. However, the machine tool use environment is different, if the environmental conditions are too bad, oil mist, dust is serious, such as when machining iron castings, the CNC system must be added to a certain degree of protection, because the CNC circuit board printed circuit board line is very dense, processing The flying dust will fall on the printed circuit board. Adding oil mist will make it firmly adhere to it. As time passes, it will cause a short circuit and cause a failure. Regular maintenance, careful use of some CNC machine tools, its numerical control device on the protective door, each time the switch protection door numerical control device's cable will then be bent, long-term, it will lead to the cable or its joints part of the broken and virtual connection and cause failure : Some CNC machine tools, the cables connected to the servo motor are exposed outside and moved along with the carriage, or dragged on other parts. The cable breaks down and fails for a long time. Therefore, CNC machine tools must be regularly inspected and maintained, especially cables, and they should be replaced if they are found to be damaged, broken or falsely connected to prevent malfunctions. In addition, the servo motors used in CNC machine tools are different from ordinary motors in that they are equipped with pulse encoders and position detectors, which are consumable parts. In particular, pulse encoders are glass and they are bonded with epoxy resin. fragile. Therefore, for the servo motor, do not use the hammer to beat the assembly: use prohibited parts, rough and other heavy objects collide or placed on it.
