Several methods and applications of the most popul

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Several methods and applications of diagnosing difficult faults of CNC machine tools

several special methods and examples of diagnosing difficult faults of CNC machine tools Abstract: a new programming method for machining elliptic curves by CNC machine tools based on the reference diagram of austenite grain size of W18Cr4V Steel (I) Using Siemens 840D to transform the grinding machine of CNC gantry machining center introduces CATIA module Chinese English comparison of motor and screw transmission ratio calculation research and development of CNC system software chip diamond semiconductor with strong conductivity has been introduced automobile manufacturing equipment innovation drives the development of related industries practical AutoCAD additional tools and system variable frequency converter application in the instrument panel with soft rubber instead of hard rubber to adjust the cutting parameters of machine tools Chongqing Machine Tool Plant No. 3 Three new products were rated as high-tech products with 0.618 method. Among them, the spherical structure can carry the software structure of the CNC system for the processing of medicinal chilled cast iron rollers around the body (cme988). The three elements of drilling processing Kellenberger cylindrical tool grinder cotton carding machine feed roller bearing transformation how to control UG dwg/dxf or IGES Research on the mechanism of improving the wear resistance of yw1 cemented carbide blade by cryogenic treatment in the computer control system of the default multifunctional laser processing machine output from step conversion file [label: tag] 1 The resistance comparison method is used to diagnose the short-circuit fault of power supply load. An example of fault: fanuc-besk servo drive board ten 15V load soft breakdown and fuse burning. During maintenance, we determined that the cause of the fault was local short circuit of the load through preliminary inspection, and measured the 15V ground resistance with a digital meter. The normal board was 1.3k, and the fault board was 300. Because it's easy to burn a fuse when powered on, it's impossible to check when powered on

1. The resistance comparison method is used to diagnose the short-circuit fault of power load

fault example: FANUC Besk servo drive board + 15V load soft breakdown and fuse burning

during maintenance, we determined that the cause of the fault was local short circuit of the load through preliminary inspection, and measured the resistance to ground of ten 15V with a digital meter. The normal board was 1.3k, and the fault board was 300. Because it is easy to burn a fuse when powered on, it is impossible to check when powered on, so we can only do resistance measurement or component removal inspection

however, since the ten 15V power supply of the servo board and the printed circuit of its load (24 integrated components) form a radial structure, if the resistance measurement fails, the circuit can not be cut and separated, and because there are many components and they are directly welded, it is impossible to disassemble and inspect them one by one. The actual operation of maintenance is very difficult. Even if the fault is solved, the circuit board is often scarred. It is very convenient for us to use the resistance comparison method to deal with this kind of fault, which can neither be cut and separated from the circuit nor disassembled from the components nor checked with power on. During the diagnosis and inspection, the circuit is not cut and the components are not soldered off, but the resistance value between the 15V terminal and the relevant pins of the integrated components is directly measured, and the fault board is compared with the corresponding value of the normal board at the same time, so as to detect the fault. When dealing with the above faults, considering the number of component pins, first analyze the internal circuit of thick film block (marked in the figure) and the function diagram of integrated block pins, and then select several main test points for resistance measurement. When measuring Q7, it was found that the resistance of its 3 pin (+ 15V) to 14 pin (output) was 150 (6K normally), and it was suspected that there was a problem with Q7 (LM339). After replacing Q7, the servo board returned to normal, indicating that the abnormal resistance between Q7 pins was due to internal soft breakdown, resulting in a short circuit of the power supply

2. Step by step simulation method of fast process

some control processes, such as the automatic speed up and down process of stepping motor and the parking braking process of DC governor, have only a few tenths of a second. It is obviously impossible to use general instruments for fault tracking and detection to search for circuit faults in this fast process, so fault diagnosis is more difficult. Next, through the fault example - the fault that the main drive of 5V DC thyristor stops for too long, we introduce the special method we use - step-by-step simulation method

after the preliminary inspection of the fault board, it is judged that the fault is caused by the braking circuit of V5 main driver. The braking control logic is complex and involves many circuits, so it is not easy to diagnose the fault. Moreover, because the braking process is short and cannot be measured, we use the step-by-step simulation method for diagnosis and inspection. According to the circuit principle, the braking process is as follows: (1) the bridge inverts to release energy; (2) Automatic axle change and regenerative braking; (3) Change the bridge again and the circuit is restored

in order to meet the needs of step-by-step measurement, take speed command, speed feedback and current feedback as set values, divide the above process into eight steps (listed in a table), and then gradually change the corresponding set values, detect the relevant circuit signals, compare the circuit logic, and find out the fault. We did the step-by-step test. When we went to the second step (i.e. the speed command changed from 1 to 0), we found that both the a backward shift and the integral stop were at the high level. According to the circuit logic, they should be at the low level. According to this, we checked the circuit and quickly found out that there was a problem with the NAND gate dl06 (model: fzhi01) in the A2 board. After replacement, the fault was eliminated

a special fault of 4-os3 frequency detector

ct4-os3 frequency converter is commonly used in the tool magazine drive of ybm90 and mk5oo machining centers. During the maintenance, we have encountered the phase failure of the frequency converter many times, and the measured phase failure voltage is only 60 to 2oov (normally 400V). As this is a kind of soft fault, it is difficult to diagnose and search

however, we found that most of the faults of the frequency converter were caused by the unstable oscillation of the pulse isolation stage. This kind of fault phenomenon is difficult to find the loss of waveform when checked with oscilloscope, but generally there are three groups of pulse amplitudes that are not equal, or even the difference is soft

in fact, we can see the problem by carefully analyzing the characteristics of the isolation stage circuit. This is a special intermittent oscillator. Only two three-stage transistors are used as the power switches of the oscillator and oscillator respectively. Since single tube oscillation is adopted, and the oscillation circuit is connected in series with current limiting resistors and two triodes, plus the output load of the transformer, the oscillation circuit has large loss and low gain, which is easy to cause the problems of accidental vibration stop and insufficient pulse amplitude of the circuit, that is, the motor phase failure occurs from time to time. From the above analysis, it can be seen that this circuit has strict requirements on the Q value and triode value of pulse transformer. When users repair, the following measures can be taken to make up for it: (1) select high (120 to 180) oscillation tube; (2) Appropriately reduce the resistance value of current limiting resistance, that is, connect 100-270 on 51 resistance in parallel

4. Diagnosis of multiple fault syndromes

the following is a typical example of cvt035 transistor DC driver to illustrate the diagnosis method of multiple fault syndromes. The preliminary inspection of the fault servo board shows that the appearance of the circuit board is very dirty, and the output stage is seriously burned. It can be seen that the maintenance of the user is relatively lacking. To deal with this kind of fault, we should first remove the dirt and repair the output stage. Do not turn on the power rashly, otherwise it may cause a short circuit and expand the fault surface. For example, iron dust is the conductive short circuit of the only national engineering laboratory in the field of coating, adhesive and other surface materials in China, and the short circuit of the output stage switch tube breakdown to the front stage and power supply, etc. After the above treatment, the power on inspection found the following faults: (1) the undervoltage red light sometimes flashes (ready green light flashes); (2) The motor does not rotate; (3) Switching power supply (15V) transformer TL and power switch tube v69 are abnormally hot

this is a typical syndrome, and there may be some causal relationship between faults, so fault handling needs to be carried out in sequence, otherwise it may get half the result with half the effort, and even cause the expansion of the fault surface. Through analysis, we make the following maintenance sequence: switching power supply I> undervoltage lamp> motor operation. First, check the power board. After measuring the 150V DC voltage of the main circuit and disconnecting the 15V load, it is known that the fault is inside the switching power board. In the inspection of the power board, it is found that the voltage of the 10V regulator V32 is only 9.5v. Therefore, check it and find the cause of the fault: the current limiting resistance rl85 of V32 becomes larger. After replacing rl85, the 15V power board and undervoltage lamp returned to normal, but the motor still did not turn. It can be seen that the flashing of the above lights and the scalding of components are caused by the rl85 value change, and there are other reasons for the non rotation of the motor. According to the usual inspection method, it can be detected step by step, but due to experience, we only did a simple change steering test, and it was found that the reverse operation was normal, so we quickly found out the cause of the fault: the integrated block N5 (tl084) of the commutation circuit failed, and everything was normal after N5 was replaced

interface method

because the signal transmission and control between each unit of the NC machine tool (except the driver) and the NC system are realized through the PC interface (1/O), many faults will be reflected through the PC interface signal. We can diagnose various complex machine tool faults or judge whether the fault is in the NC system or in the machine tool electrical by consulting the 1/O signal on the side of the PC machine tool. The method is very simple, that is, it is required to be familiar with the current state and normal state of all PC (machine tool side) interface signals (or make a table). During diagnosis, check and compare the current state and normal state of all PC (machine tool side) interface signals one by one, find out the faulty interface signals, and then find out the cause of the fault according to the external logical relationship of the signals. When you are familiar with the PC interface signal, the application of this PC interface comparison method is very simple and fast, and avoids the complex ladder program of board division

6. Recovery of abnormal data of Siemens 3GG system

the Swiss learner s45-6 grinder is equipped with Siemens 3GG system, which is a dual NC dual PLC structure. The system has a strong self diagnosis function. When a fault occurs, it can quickly diagnose and repair the fault with the help of screen prompts. However, if the system cannot be started, and the PLC is stopped and the screen is not lit, the self diagnosis function of the system will not work, resulting in difficult diagnosis. There are many reasons for this failure. If the battery voltage is lower than 2.7V, the battery must be replaced; If the NC or PLC hardware is damaged, the circuit board needs to be replaced; If the 24V power supply of the machine tool is lower than 21V, check the power circuit and load

however, the reason we encounter more failures is not hardware failure, but software failures such as abnormal machine tool data. The reasons are complex, such as electrical interference, electromagnetic wave interference, battery failure, operation errors, etc., which may cause the loss or confusion of machine tool data, so that the system cannot be started

for such soft faults, we can use the full clear recovery method to recover the system. The full clearing steps of 3GG system are as follows:

(1) clearing machine data, user program, setting data and background memory; (2) Initialization of 3GG system; (3) PLC reset; (4) Recover all data and programs that have been cleared. Generally, you need to set the baud rate, call out 128KB memory, and then input data and programs through disk and other media. (5) Test and check all kV coefficients of the servo system. (6) After completing these steps, the system returns to normal

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