: Introduce the electrical transformation of the milling machine and the application of the programmable controller on the milling machine.
The 2mx7m gantry milling machine is the original Soviet-made product in the 1970s. The equipment has been idle for many years, the electrical components and electrical systems have been damaged, and the technical data has been lost. The original system cannot be repaired. In order to re-work the equipment, electrical renovation must be carried out. .
1 Reconstruction plan After the mechanical action mapping, the electrical schematic is redesigned. The control system adopts OMRON programmable controller, and the action is controlled by the logic of the PLC program. The vertical milling head mast rotation is driven by a 55kW DC motor. The DC speed control system is driven by a Siemens 6RA70. The side milling head sleeve is driven by a 30kW AC motor. The feed movements of the vertical milling head, side milling head and table are driven by 4 sets of KSA23 DC speed control systems. The sleeve inlet and outlet and the slide lift of the side milling head are controlled by a system controlled by a solenoid valve.
2Electrical principle The control power supply of the machine tool adopts isolated 220V, and the operating circuit uses DC 24V power supply to ensure the safety of operators. The main power supply adopts three-phase 4-wire system, and the input end is added with leakage protector to ensure equipment and personal safety. The DC speed control system is equipped with a power contactor, so that the system can be connected to the main power supply when it is ready. In the fault state, the main circuit power can be quickly cut off.
The operation of the machine tool is controlled by PLC, which simplifies the operation of the line and improves the control accuracy. The PLC input uses 7 16-point input cards of ID 212 type, sharing 99 input points. The output uses three 32-point transistor output cards of the model OD213. Share 84 output points.
Both the input and output modules require a DC 24V power supply, the output module is a transistor output unit, and the module power supply is connected according to the polarity of the module.
The output point has a maximum capacity of 16 mA, so each output point has a small intermediate relay, and the intermediate relay controls other electrical components. The CPU of the PLC selects CQM1H-CPU21, which can be up to 256 points, and the program capacity is 3.21 dry words, which can support RS232 interface.
First, draw an electrical schematic based on the electrical components required for the machine. Determine the address of the electrical component in the PLC, and then based on the action and working principle of the machine tool, draw the ladder diagram of the PLC (ie PLC working program) in the computer, and compile the PLC program using ORMON's SYSMAC-CPT program development platform. Offline programming and online debugging.
In the design of the ladder diagram, in order to protect the safety of the machine tool and the system, the control loop and the speed control system are equipped with power transmission contactors, and the machine must first control the power transmission before working. In order to prevent the machine from malfunctioning, all the selector switches can be controlled to transmit power when they are in the “zero†position. Similarly, the main drive and each feed system send power, and each control switch needs to be in the "zero" position before the power transmission operation can be performed. After the system is powered, the preparations for the machine start to work. If the hydraulic pump is started, the clamping block is loosened, the excitation is powered, etc., all the conditions are available, ready to be powered, and the indicator light on the operation panel is on, and the positive and negative motion operations can be performed. In the process of movement, in order to prevent the machine from being stopped due to misoperation, self-locking is used in the control, so that changing the direction of movement, shifting, etc., must be performed after the movement is stopped. The main drive is stopped in two cases. One is that the main drive works separately, and is executed immediately when the main drive is stopped. In another case, when the main drive is working, the feed motion is also working. When the main drive is stopped, the feed motion is stopped first, and the main drive delays after 1 d. This design is to prevent the knife from being used when parking.
The clamping and loosening work of the vertical milling head ram and the slide is more complicated. When the ram is selected, the hydraulic motor starts to work. The hydraulic oil pushes the clamping block through the hydraulic cylinder to relax. When the seat is relaxed, the relaxation limit action signals and the hydraulic pump stops working. . When the skateboard is not selected, the ram needs to be clamped. First, the hydraulic pump starts to work, the clamping solenoid valve is energized, and the hydraulic oil pushes the hydraulic cylinder in the opposite direction to drive the clamping block to clamp the ram. In order to reliably clamp the ram, the hydraulic pump stops for 15d, the clamping solenoid valve is de-energized, and the clamping process ends. The clamping and relaxation process of the vertical milling head slide is the same as the movement of the ram. Since the ram and the slide can work at the same time, the ram and the slide can be clamped and relaxed separately. You can also clamp and relax at the same time. Since the slide plate and the ram share a hydraulic pump, the hydraulic pump is started and the hydraulic pump is stopped after the end of the clamping and relaxation operation. The clamping and relaxing action of the ram and the skateboard can work both alone and at the same time. In order to realize this process, in the design of the ladder diagram, the intermediate relay is used to preset, and the internal time relay is used to control the action time, and the logic control of the PLC is used to realize this process.
Special fault handling of high voltage secondary circuit Wang Weiyinqiang: Introduce the analysis and treatment of the secondary fault of the secondary circuit of 6kV power supply system.
After the transformation of the power supply system of our bureau, the 6kV system was put into trial operation. During the trial operation of more than one year, the secondary circuit has repeatedly failed, and the staff often checks the conventional faults such as circuit disconnection, terminal connection, contact sticking, and component burning. Due to the special structure of some components, the faults exhibited are also unique. From the careful analysis of the principle structure and working characteristics of electrical components, we should analyze and judge faults, which will greatly help us deal with faults. Now we will introduce the faults and processes we have encountered as follows.
Test, after there is no syntax error, connect to the computer and transfer the PLC program to the CPU. You can perform online debugging by switching the working status to monitoring. The on and off of each unit in the ladder diagram is visually displayed on the computer screen. It is also possible to force the continuity of each unit when needed, so that the program can be smoothly carried out during commissioning. The program debugging can detect the logic relationship of the program, whether the machine wiring is correct, and whether the electrical action meets the design requirements. When the program error is found, it can be modified offline, and then modified and then connected to the PLC.
After all the programs have been debugged, the machine is linked to the test. Adjust the detection components and control components of each part of the machine tool to match the movement of the machine tool. When the mechanical action is in place, send a signal to the PLC. After receiving the signal, the PLC controls the machine tool movement according to the program.
The main drive motor of the vertical milling head is a 55kW DC motor. The drive unit uses Siemens 6RA7081-6DV62 DC speed control system. The system adjustment is all set by parameters. First set the system incoming power parameters (to ensure the stability of the system power supply, a three-phase compensation type power regulator is installed at the incoming power supply to ensure stable power supply). The main power supply and the excitation power supply are set to 380V. Then the motor parameters are set. The motor parameters to be set are P100~P113, and then the motor working mode parameters P81, P82, P83 and P741 are set. After the parameter settings are completed, the system is automatically optimized. Automatic parameter optimization is divided into current loop optimization, speed loop optimization and excitation optimization. In the optimization process, the system automatically detects the motor performance and optimizes the configuration of relevant parameters.
After the optimization is completed, the system can work normally. Start the spindle to see if it can meet the working requirements. If not, adjust the parameters P303 and P304 to change the system rise and fall ramp functions. After the operation of the actual air blower motor overcurrent relay, the air blower motor cannot be self-protected. The air blower motor has an unexplained fault during the test run. The accident notice signal is not displayed, and the check notice signal is faulty. After the motor is started for a few days, the motor does not know the cause of the fault and jumps. After careful inspection and analysis, it is found that when the overcurrent relay is activated, the pre-announcement signal is set to 0.5 = to meet the working requirements.
3 Effects After the electrical transformation of the machine tool, all electrical components are new series products. The advanced technology is reliable and the failure rate is extremely low. The performance parameters of the machine tool have met the work requirements. The vertical milling head mast rotation is smoothly adjusted from 10r/min to 650r/min, and the table feed varies from 10mm/min to 3000mm/min, which can meet the requirements of low speed feed and high speed tool setting. The workbench also has a fast moving function driven by an AC motor. When the workbench is fed at a low speed, the communication is started quickly, and the workbench can be quickly operated in the fast direction of the selected communication. After the stop is fast, the workbench resumes the original feed motion. The rams and slides of the vertical milling head and the slides of the horizontal milling head are selected from the KSA23 DC speed control system. The speed ratio is 1000, the low speed performance is very good, and the machine meets the requirements of the low speed feed of the machine. All kinds of processed workpieces are tested and qualified.
4 Conclusion With the continuous development of science and technology, many new technologies are more and more widely applied to factory electrical automation. The 2mx7m gantry milling machine uses PLC program control technology, and the DC speed control system uses thyristor rectification technology. The thyristor speed control system realizes digitization, and the control precision and machining accuracy of the machine tool are greatly improved.
Received from the end of November, 2003, æ›° Fan Dongsheng, Xu Bin: Wang Yongtang, engineer of heavy equipment repair factory of Yizhong Group Co., Ltd., assistant engineer of heavy equipment repair factory
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