CNC machining equipment is a set of technology-intensive and knowledge-intensive mechatronics products of CNC machining centers. Its technology is advanced and intelligent, the control system is based on integrated circuits, the structure of the CNC machining center is cumbersome, the long-term operation of the CNC machining equipment is complex, and the maintenance is difficult. The fault diagnosis and maintenance of CNC machining equipment is an important link in its use process, and it is also one of the factors that limit its full function. The fault types of CNC machining equipment are generally divided into two categories: display content and non-display content.

The working principle of CNC machining equipment

CNC machining equipment is mainly composed of input and output equipment, numerical control equipment, servo drive equipment, machine tool electrical logic control equipment and orientation detection equipment. Its working principle is: in the process of processing, the processing size and processing data are input into the numerical control processing program according to the code and format specified by the system, input into the numerical control equipment through the input and output equipment, and the data is processed by the program to convert various processing information. And the instructions are output to the electrical logic control equipment and servo drive equipment of the machine tool, and then control the transmission equipment to make the machine tool cooperate with the cutting process of the workpiece. In this process, the servo drive equipment not only receives the instructions of the numerical control equipment, but also exchanges information and signals with the electrical logic control equipment of the machine tool, so that the cutting precision of the workpiece is higher. In the CNC machining process, the orientation detection equipment detects and monitors the data of each moving part, and feeds back the data and monitoring results to the CNC equipment in real time, which is convenient for the data operation and accurate control of the CNC equipment, and then forms a useful semi-closed loop control for the CNC equipment. . CNC machining equipment has many faults in operation, and the types of faults corresponding to different types of CNC systems are also different. However, they can be divided into two types: system failure manifestations and system failure manifestations. The two faults are briefly described below.

2. System failure

(1) Servo drive failure.

Fault phenomenon: A CNC lathe (type: CKA6136) adopts FANUC OTC system. When the CNC system starts, the alarm number is 401: "servo X axis vrdy disconnected"; 403: "X axis CNV low voltage DC link", the processing program cannot run, and all parts of the equipment cannot run.

Fault analysis and inspection: According to the FANUC maintenance manual, the 401 alarm description is as follows: the CNC system is not servo controlled, and the signal is ready; 403 alarm description: the DC voltage of the servo drive is reduced. After checking the electrical schematic diagram of the machine tool control system, it was found that the contactor KM1 of the servo drive power supply was not pulled in. The KM1 is controlled by a servo system. Check whether the 220 V DC 24 V input and output of the power supply module is normal, check whether the DC 24 V voltage drop of the servo drive power module is normal, and measure whether the servo drive power plug has no DC 24 V output. Further check if one of the power wires in the CXA19B plug shown in Figure 3 is disconnected, resulting in no DC 24V input to the servo drive, so the normally open point of the module CXA29 in Figure 1 cannot be closed. Therefore, after the servo start command is issued, the contactor KM1 coil in Figure 1 cannot be energized, resulting in the power failure of the servo drive, resulting in a malfunction. The principle is shown in Figure 1 and Figure 2. Troubleshooting: Re-solder the disconnected power cord of the CXA19B plug of the servo drive for trial operation. The system alarm is lifted and the equipment operates normally.

(2) The encoder is faulty.

Fault phenomenon: R560 drilling and milling CNC machining center using Mitsubishi 60s system (Mitsubishi system) suddenly stopped working during the normal operation of the machine tool, showing: Z70 0001Y; SO1 PR 0018Y alarm clock.

Failure analysis and inspection: Check the maintenance instruction Z70 0001 Y alarm, saying that the Y-axis servo motor is invalid, the certain orientation encoder S01 PR 0018 Y alarm, saying that the Y-axis servo motor certain orientation signal cannot be executed, it is composed of two kinds of alarm messages, which are basically determined A certain orientation is the origin orientation caused by the abnormality of the Y-axis servo motor encoder. According to the principle analysis, the possible reasons for the abnormal origin orientation are: the servo motor encoder plug is dropped, the servo drive is damaged, the digital quantity