CNC reformation of g-type rut Dongguan Institute of Technology (Guangdong 523IU6) Liqi CNC machine tools are increasingly used in the machining industry. The development of CNC machine tools is full-featured and high-performance on the one hand; on the other hand, it is a simple and practical economical CNC machine tool with basic functions of dynamic machining and convenient operation and maintenance. The economical numerical control system usually uses an open-loop stepping control system. The stepping motor is a driving component and has no detection feedback mechanism. The positioning accuracy of the system is generally up to ±(0.01~0.02)mm, which can meet the processing parts of the C6M6 lathe. The accuracy requirements. After several overhauls, the horizontal lathe has a large change in the size of its components. The main transmission parts have been replaced and adjusted, and the failure rate is still high. It is difficult to meet the overhaul acceptance standard with traditional repair solutions, and the cost is high. . Therefore, the rational selection of the CNC system is the main link for the success of the transformation. The transformation of CNC machine tools requires the machine to be stable and reliable with the lowest possible failure rate. The horizontal lathe is modified by a microcomputer control system to improve the process level and product quality and reduce the labor intensity of the operator. The microcomputer control system will be used to summarize and analyze the C6146 lathe transformation process. 1. Selection of Microcomputer Control System At present, there are many types of CNC systems on the market. Before choosing, the first step should be to fully understand the functions of the CNC machine tool to be modified. The CNC system can be selected according to the principle of reasonable price, advanced technology and convenient service. In the case of economic ability, try to use brand-name products. Such numerical control system has strict screening of parts and reliable manufacturing process specifications, and has excellent preventive effect on equipment failures caused by failure of electrical components or premature failure. And pay attention to the function selection of the CNC system. The high-performance index of the CNC system should not be pursued purely, which is very important for achieving a high performance-price ratio. The functions of the numerical control system should be matched with the functions of the CNC machine tool that is ready to be modified, and the excessive numerical control function should be minimized. Because of the excess function of the numerical control system, on the one hand, it is a waste of funds, on the other hand, it may also lurk under the hidden trouble of the increase of the failure rate due to the increase of the complexity of the numerical control system. Therefore, the machine control system of the machine tool was selected according to the structure, performance and precision of the machined parts. That is the GSK/928T type CNC system. The control computer uses a high-speed microcomputer processor, a semiconductor memory, and a parallel interface circuit. The driving part adopts transistor PWM drive circuit, the whole system belongs to open-loop control, the structure is simple, the driving force is large, the price is low, the anti-interference performance is strong, the quality is stable and reliable, the installation and debugging is convenient, especially the teaching programming function is directly to the operator, very Suitable for medium and small batch production. In order to give full play to the technical performance of the GSK/928T numerical control system, it is ensured that the modified lathe is repeatedly positioned under the system control, the microcomputer feeds without creeping, the service life is long and the appearance is beautiful, and the mechanical part is made/modified as follows. In order to make the modified machine tool have higher starting rate and precision retention, in addition to reducing electrical and mechanical failures as much as possible, the wear resistance of machine parts should be fully considered, especially the wear resistance of machine tool guides. a large size of the former domestic and foreign CNC machine tools, such as ordinary cast iron. The guide rails are made of hardened alloy steel, which has a wear resistance 5 to 10 times higher than that of ordinary cast iron guide rails. According to this, the old bed is used in the transformation, and the GCR15 bearing steel is hardened to 65-degree guide rail, and fixed on the cast iron bed with screws and adhesives. The working surface of the guide rail before bonding is ground, surface roughness The main motion mode requires a very wide range of shifting speeds as in the case of conventional machine tools to ensure a reasonable cutting speed during processing, resulting in higher productivity and quality of the agricultural surface. According to the specific conditions of the original headstock shifting, the 16 kinds of spindle shifting S functions provided by the numerical control system in the coding mode are effectively utilized, and only the double gears of the 56 and 51 on the I axis and the 34 and 39 on the shaft are provided. Divided into two, on the 56 and 51 each installed DLM3 command to complete two kinds of speed regulation, other speed group adjustment, can use the system to stop the start command, using the original manual mechanical shifting to complete. The transmission of the M part of the modification section is shown in the drawing. g(3) The object directly controlled by the saddle bed saddle system, whether it is point control or continuous control, the final coordinate accuracy of the machined part will be affected by the accuracy, sensitivity and stability of the saddle movement. For the application of stepper motor for mechanics ((cold machining) 2 (m year 11th technical exchange dragging the iF ring system is especially good because the command issued by the numerical control system only makes the position detection and signal when the saddle is moving Feedback, so the actual movement value and the system command value will cause machining error if there is a difference. Therefore, in addition to the high accuracy requirements of the saddle and its accessories, the following measures should be taken to meet the transmission accuracy and sensitivity requirements. The reduction gearbox is used to improve the transmission torque and transmission accuracy (resolution is 0.01mm). The transmission ratio calculation formula is: P screw pitch, mm 8 pulse equivalent (ie resolution), mm in gear transmission, to improve The anti-transmission accuracy must eliminate the transmission gap between the mating gears as much as possible. There are two methods, the flexible adjustment method and the rigid adjustment method. The flexible adjustment method refers to the method that the gear backlash can be automatically compensated after adjustment. In the case of differences in tooth thickness and pitch of the gear, there is still no backlash engagement, but it will affect the smoothness of the transmission, and this adjustment method Compared with the complex P, the transmission stiffness is low. The rigid adjustment method refers to the adjustment method that the gear backlash cannot be automatically compensated after adjustment. It requires strict control of the tooth thickness and pitch error of the gear, otherwise the flexibility of the transmission will be affected. The gear transmission adjusted by this method has better transmission rigidity, and the structure is relatively simple. The matching gear backlash method applied in the equipment transformation is the rigid adjustment method. The ball screw is used instead of the original sliding screw to improve the transmission sensitivity. Reduce the power slaughter, stepper motor torque damage fire tool change device, two feet in a machine tool 12 - secondary clamping complete multi-step plus 1: and application GSK / 928T CNC system T function, after many investigations and trials Finally, the WZD4 automatic tool holder is used. This tool holder can not only replace the horizontal lathe manual tool holder, but also can be used as the microcomputer control component of the CNC machine tool. The tool holder is small in size and has high repeatability and is suitable for powerful turning and safety. M is reliable. Remove the original slide box and use this position to install a new slide box. In addition to the nut of the fixed ball screw, the new slide box is internally provided with a storage tank and a hand pump for lubricating the screw pair. : The hanging wheel box and the feed box are removed. In these two positions, the spindle pulse encoder for controlling the thread processing, the power stepping motor for the saddle axial servo element and the reduction gear box are respectively installed. Make the modified machine tool look beautiful and reasonable. After the transformation, the start and stop of the machine tool are completed by the numerical control system, so the original machine tool joystick, the levers such as the turning bar and the vertical shaft are removed. After the modification of the lathe, not only the original machine tool spindle transmission part has a wide range of shifting speed, but also can be programmed and controlled by the programming language in the machine motion control. The operator can automatically generate the ISO code during the system teaching state. The ft-moving of the next part has proved that the machine is easy to operate, reduces the labor intensity of the operator, improves the quality of the product, and creates favorable conditions for the next process. The cost of the transformation is only the purchase of the price of the simple CNC lathe. half. (Received period) Taiwei Caofu Dandong 518 Internal Combustion Engine Parts Factory (Liaoning 1 18009) Yao Guangying Teng Haiping The machine table is a turntable type. There are two fixed cylinders on the turntable, and the cylinder liner is pressed from above. During operation, one cylinder presses the cylinder liner, the honing head hones the inner hole, and the other cylinder is released. The operator removes the cylinder sleeve from the clamp and measures it. If the size is not acceptable, you need to reinstall the fixture for honing. Since the cylinder liner must be removed from the fixture, often a cylinder liner is clamped several times, affecting the machining accuracy. To this end, we have designed a cylinder holder that works well. The structure of the fixing frame is shown in the drawing, the cylinder is fixed on the cylinder support 1, and the cylinder support 1 is fixed on the cylinder support frame 3 by screws and positioning pins, and the adjustment center rail 2 is used to ensure the center line of the cylinder and the honing head. The center lines coincide. The cylinder support frame 3 is spanned on the ground on both sides of the table where the table is connected to the bed, and is fixed by anchor bolts. When working, when the cylinder liner is turned to the cylinder support, the cylinder is pressed against the workpiece, the machine tool begins to honing the cylinder liner, and the other cylinder sleeve to be processed is placed in the positioning ring. When the workpiece is honed, the table rotates 180°, and the cylinder sleeve to be processed is turned to the machining position. The finished cylinder sleeve can be directly measured without moving the cylinder liner. It avoids the detection method of taking out the cylinder sleeve from the clamp cylinder 2. Iron rod 3. Cylinder support frame, which improves the inspection quality and reduces the labor intensity, and is welcomed by the operators. () - Mechanical workers (cold processing) (Finish)
The insulation breakdown accident often occurred in generator. It includes interphases short circuit, inter-turn short circuit and ground fault.
The interphase short circuit: the generator windings ends will be greatly impacted by electric power and may make the coil end deformed under two-phase or three-phase short circuit and differential protection tripping happening.
Inter-turn short circuit: Generator outlet blasting, if it continues a long time, the stator copper wire will be melted. When no-load run, the generator three-phase voltage will be imbalance.
Ground fault: Generator breakdown location is in the linear portion or notch position and stator ground protection act. The insulation resistance value between stator ground and ground is zero or minimum.
The fundamental reason of generator insulation breakdown is that the stator coil insulation is weak or there is a corona etching in notch in run time. The treatment method is to find the point of breakdown and reworked and reinforced insulation. At the same time, eliminating the corona etching in a maximum extent is important.
III. A large noise or vibration with generator
The reasons of a large noise or vibration with generator are:
1. Foundation bolts loose, or STG subsidence. Treatment: fastening bolts. Recalibration concentricity.
2. Generator rotor and Steam Turbine shaft are misalignment. Treatment: calibration concentricity.
3. Bearing wall worn or damaged under short oil. Treatment: repaired bearing or replace a new bearing with same model.
4. There is a friction between the stator and rotor. Treatment: find the friction location and reason, and then eliminate it.
5. Fan or other fasteners loose. Treatment: Tighten fan and fasteners.
6. Rotor coil partial short circuit, two points grounding or wiring errors. Treatment: please inspect the insulation of slip ring and the rotor coil to the ground. Or connect to the DC power source and check the voltage drop of each coil, winding direction and wiring method. So we can identify the cause of the malfunction and eliminate them.
7. Brush is too hard, or the pressure is too large. Treatment: adjust the pressure or replace the same type of brush.
8. Three-phase current are severe asymmetry. Treatment: please investigate that the three-phase current imbalance is in the allowable range or not. If it is not in the allowable range, please adjust three-phase load or reduce the load.
9. Stator winding short circuit or ground. Treatment: Find out the fault and repair it.
10. External fault or lightning strike. Treatment: if the vibration time is too long, please stop the STG and inspect.
Typical
cases:
This is a 15 MW generator from a Shandong customer. The vibration of generator is reached to 0.12mm in running. After inspection the generator, we found that rotor dynamic AC impedance upheaval 12% in 2400-2700 and the dynamic inter-turn short circuit is serious. It destroys the balance of the magnetic field and causes the electromagnetic force uneven of generator rotor. After removal of the rotor retaining ring and treatment the rotor inter-turns, we start the STG. The vibration is about 0.01mm.
IV. The temperature of a generator is too high.
Generally the temperature of a generator will be in the allowable value, if the generator running normally and the current, voltage, frequency, power, excitation current and power factor are all within the allowable fluctuation range. If a generator stator, core and other parts temperature are too high, please consider the following cases:
1. Generator overload operation and exceed the allowable time. Treatment: Please reduce the generator load to the rated load or under rated load as soon as possible.
2. Three-phase current are serious imbalance. Treatment: please find out the reason of imbalance. If it is the voltage causing, please check if it is the generator inter-turn short circuit. If it is load causing, please adjust the load and make it balance.
3. The ventilation cooling system of generator is poor. For example, the temperature is too high, the air duct or exhaust duct are blocked, the coil and its ends are serious fouling. Treatment: please reduce the load suitability, improve ventilation, and remove fouling.
4. The stator winding portion short circuit or ground. Treatment: Find out the short circuit or ground point and repair them, and then eliminate short circuit or ground risks.
5. Insulation of the stator core may be partially damaged and short circuit, so there is a vortex and overheat. Treatment: please reduce the load suitability. If the generator reduces its efficiency obviously, please repair the generator stator core.
6. The bearing is short of lubricating oil. The oil number is wrong. The oil quality is bad. The bearing is installed with a wrong way or the bearing is damaged. Treatment: please find out the reason and then replace the oil or clean, adjust or replace bearing.
V. Generator rotor ground
Symptom: Generator grounding one point or two points grounding light plate light.
Fault Analysis: Generator rotor winding insulation damage, coil deformity and severe dust and greasy attached in the ends seriously are all leading to the grounding of the generator rotor windings. When the generator rotor winding grounding in one point, there is electrical current pass as the ground does not constitute an electrical circuit.
However, after one point grounded, it is easy of leading another grounding point. If any part in excitation circuit ground, it can form ground fault of two or more points ground. It is very dangerous.
After the failure, the rotor windings are short-circuited. Because of the small winding DC resistance, the excitation current will increase. So the magnetic field of generator is out of balance, and main magnetic flux reduces largely. So the STG will vibrant strongly. Meanwhile the power factor of the generator will be increased significantly and get into leading phase running (absorption of reactive power from the grid).
The stator field becomes in the frond and the rotor field becomes in the back. It will make the stator current increases. If the watcher notice that there is no excitation varying but the excitation current and stator current suddenly increases, and the excitation voltage and AC voltage are all suddenly drop, and power factor meter indicates increasing or leading phase, it means the generator rotor grounded or inter-turn short circuited. You should shut down the STG and blow-out magnetic. Please inspect the excitation system and rotor windings, and find out the short circuit point and treat it.
VI. Excitation upgrading and generator test
Excitation system upgrading, brushless exciter changes into the SCR excitation and make the generator maintenance easily. And it removes the disadvantage of brushless excitation dynamic adjustment slowly. The generator test includes stator insulation resistance test, the absorption ratio test, the iron loss test, leak test, AC and DC voltage withstand test, the rotor high speed balancing and overspeed test, dynamic and static AC impedance test, the generator no-load test, short circuit test, temperature rise test, residual pressure measurement, axis voltage measurement.
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