[Keywords] side wall gantry double-head spot welding machine, single-sided spot welding, PLC control [ Abstract] Through the early import of large equipment side wall gantry double-head automatic spot welding machine for electrical system transformation, using MED controller for spot welding parameter cycle control, with Fuji G9 series inverter for gantry operating system The speed is controlled, and the whole system is controlled by the programmable controller C200H. The practical operation proves to be an effective method for improving equipment utilization and operation reliability. 1 Purpose and task The side wall gantry double-head automatic spot welding machine was introduced from East Germany in the early 1980s for automatic spot welding of side wall panels and side wall columns of railway vehicles. Due to the long running time of the equipment, the serious loss of components and the lack of spare parts, the failure rate is continuously improved, which directly affects the normal production process. Therefore, it is decided to redesign the electrical system while maintaining the mechanical system of the equipment, and adopt advanced technology. The programming controller PLC controls the operation of the entire system. 2 control system components 2.1 Welding device Figure 4 I/O module distribution of C200H modular PLC Table 1 Input signal allocation table effect effect 3 system control software design After the technical transformation of the imported automatic side wall double-head gantry spot welder with C200H programmable controller, and proven to be used for more than two years, the work is reliable and the performance is excellent. And the replacement of the components after the transformation is easy and convenient, and the user responds well. It is proved that the transformation of some early imported equipment's electrical control system with a highly reliable and easy to program PLC is an effective method to improve the efficiency and utilization of equipment. â– Author : Yu Yousheng (Wuhan Jiaotong University, Hubei, 430063) references: [1] Zhao Yuhua. Pressure welding, Beijing: Mechanical Industry Press. 1989
Article ID: 1001-2303(2000)02-0019-04
Figure 1 shows the distribution of solder joints between the side wall panels and the side wall columns. The main function of the equipment is to realize the continuous automatic welding process of all solder joints. The figure shows the running step of continuous automated welding of all solder joints.
The mechanical device of the device adopts a gantry structure, and the entire gantry frame can be longitudinally run along a rail installed on the floor of the workshop. When the gantry frame is longitudinally stepped in the direction shown in Fig. 1, the pillars of the side wall can be realized one by one. Sequential welding. The gantry is equipped with a horizontally-operated trolley, which has two resistance welding transformers and welding electrodes and hydraulic lifting devices. Two soldering-resisting transformers can realize two points of time-division welding. When the trolley is stepped in the direction shown in Figure 1 (ie, along the direction of the side wall column), all the solder joints on each side wall column can be realized. Secondary welding. The trolley is driven by a 1.5kW deceleration brake motor through the drive shaft.
The welding control device is composed of a welding transformer, a welding electrode, a main power circuit and a spot welding controller. The welding transformer was supplied by the former East German Sealindorf, model number VPA2×160. Single-sided spot welding technology. Each transformer is equipped with two electrodes, a welding pole and an auxiliary electrode (blind pole), which are respectively driven by hydraulic devices.
The welding circuit principle of a transformer is shown in Figure 2, where V1 and V2 are the main power switches. The welding cycle and welding specifications are controlled by Shanghai's Medweld.200S resistance welding controller, which is a single-phase resistance welding controller controlled by Z180 microprocessor. It not only has excellent control performance, but also provides start-up welding (300). -01, 300-02), welding end (902), fault/alarm (903) and other signals, and easy to interface with PLC input / output.
2.2 Gantry operating system
The original Dongde's gantry operating system adopts DC motor speed regulation, and the circuit is complicated. The modified gantry operating system adopts Fuji G9 series inverter to drive a four-pole three-phase asynchronous motor, and then through the reducer and bevel gear to the gantry. On the side of the drive working shaft, stepless speed regulation can be carried out through the output of the frequency converter. There are currently three speeds set: fast (50 Hz), slow (30 Hz) and slow (20 Hz).
Figure 3 is a circuit schematic diagram of the gantry operating mechanism. In the figure, FRENIC 5000G9S inverter provides easy interface with PLC input and output, with forward (302), reverse (303), speed selection 1 (304), speed selection 2 (305), inverter fault/alarm and The inverter runs (J5) and other signals.
2.3 Other auxiliary devices
Includes hydraulic controls, cooling water, fan systems, fault detection and protection systems. The hydraulic control unit consists of a three-position four-way solenoid valve, double check valve, pressure relay, pressure reducing valve and pressure gauge. Its task is to control the electrode lift and adjust the electrode pressure.
The cooling water and fan system are used to cool the welding transformer and the main power devices V1 and V2, and use the flow sensor to detect the water quantity signal. Only when these signals are normal, automatic welding is allowed.
The fault detection signal includes inverter fault, PLC fault, welding control system fault, etc., and any one of the faults will cause the termination of the automatic welding procedure.
2.4 PLC control system
According to the original function of the equipment and the newly added functions after the transformation, the control system has 70 input points and 42 output points, so the C200H modular programmable controller of Japan OMRON (Lishi) is selected and matched with input and output. Module. A C200H CPU module can expand two expansion units. The motherboard unit is divided into ten slots, eight slots and five slots. The system can provide up to 480 input/output points. There are nine types of relay units inside the C200H system, 3536 internal auxiliary relay units and 512 timing/counters. Ladder programming is used. The instruction system is rich and easy to program. It also has data processing and operation instructions.
According to requirements, the PLC system consists of a 10-slot motherboard, a CPU module, 5 ID212 input modules (16 points each), 2 OC225 relay output modules (16 points each), and 1 ID212 transistor OC gate. The output module (16 points) and one OC224 unique contact point (not 8 to each other, a total of 8 points) of the output module of the relay output, the distribution of each module in the motherboard as shown in Figure 4. The address of each module is related to the location of the motherboard slot, which can be interchanged. The type and address arrangement of each module (channel number + sequence number in the channel), and the type and function of the external device are shown in Table 1 and Table 2.
The input models of all the input modules in Table 1 are ID212. Among the 005 channels, the gantry track selection switch has two choices according to the distance of the side wall column. It is essentially the photoelectricity of one of the step distances of the gantry. The switch performs position detection. The trolley trajectory selection is matched with the number of solder joints to select the number of solder joints required for each side wall post. The detection of the stepping distance of the trolley is composed of two sets of proximity switches. When the upper track is selected, one of the proximity switches is actually selected for position detection. At this time, the number of optional solder joints is 40 and 32; when the lower track is selected, the number of solder joints is 44, 36, and 28 dots. Channel number Input signal type 005
(00~15) switch Wall panel selection, gantry trajectory selection, welding point selection, manual selection, trolley trajectory selection, etc. 006
(00~15) power switch button Manual gantry fast, slow, start and stop; manual oil pump, water pump, fan start and stop; manual car start and stop; automatic start and stop, etc. 007
(00~15) Travel switch, pressure and thermal relay contacts The front and rear limit position of the gantry, the left and right limit position of the trolley, temperature, pressure, flow and other signals 008
(00~15) Photoelectric switch proximity switch Stepping distance of gantry, photoelectric switch trolley stepping distance of step trajectory, proximity switch of step trajectory 009
(00~06) Relay contact The output of the inverter of the gantry operating system and its operating status, fault signal, its operating status and fault alarm signal output by the two MED spot welding controllers
Table 2 output signal allocation table Channel number Module model and output point type Output device type 000
(00~15) OC225
Relay contact Indicator light,
led Operating status indications for gantry, trolley, oil pump, water pump, fan, water temperature, frequency converter, Meida controller, etc. 001
(00~15) OC225
Relay contact Relay coil Intermediate relays such as left and right trolleys, fans, oil pumps, pumps, and electrodes running up and down 002
(00~11) OD212
Transistor OC gate Digital Tube Number of solder joints per workpiece (four total)
Number of weldments (four in total) <display> 003
(00~06) OD224
Relay single point Relay coil Welding start of two Meida controllers, inverter speed selection, forward and reverse control signals
According to the requirements of the system, through analysis, the operating state of the PLC control system of the side wall gantry double-head automatic spot welding machine can be divided into three states: manual, automatic and fault. Due to the many interlocking relationships in the system, the action cycle process is more complicated. Through in-depth analysis of its principle and action sequence, the PLC control software design of the whole system can be divided into five modules: manual, automatic, fault processing, display drive and integrated output drive. The relationship between the modules is shown in Figure 5.
The manual part is mainly used for pre-weld adjustment. Its main functions include the left and right rows of the trolley, the slow movement of the gantry frame, the fast movement of the gantry, the electrode lifting, the pump and the fan operation.
The fault part is mainly used when a certain part of the welder fails. First, the automatic welding procedure is locked, so that the welding process is not possible, and some manual functions are allowed to operate, so that the corresponding debugging and maintenance can be performed to make the troubleshooting more convenient.
The display driver module is the user's instruction interface. Its main function is to display the number of solder joints and the number of workpieces welded.
The integrated output module is the final drive module for the manual function and the automatic function. The program function of the manual function and the automatic function uses the internal resources of the PLC as an intermediate relay to memorize various intermediate states of the program operation. The output of the integrated output module is refreshed in each scan cycle based on the state of these intermediate relays.
The automatic function is the most complicated part of the whole control software, and is also the focus of the entire software design. Figure 6 shows the state flow chart of the automatic function simplification. The main action sequence is characterized in that the stepping cycle of the gantry includes the cycle of the stepping operation of the trolley to realize the automatic welding process of the side wall columns and the welding points one by one. The end condition of the fully automatic welding is that the gantry is quickly returned to its original position after the gantry has reached the extreme position of the forward row.
4 Conclusion
Zou Yuheng ((Wuhan Kaiqi Company)
[2] Zheng Yuping. Programmable Controller. Beijing: Aerospace University Press. 1995
[3] Li Kangbao et al. Discussion on the quality of spot welding of microcomputer controlled resistance. Electric welding machine, 1987 (5)
[4] Ren Changfu. RWC-8404 Constant Current Spot Welding Controller. Electric Welder, 1986(5)