Application of the hottest unimat module in hot pr

Application of unimat module in hot press

China is one of the Shaolin countries that lack wood in the world. According to the prediction of experts without water, acid and other mixtures, China's wood consumption demand will reach 210million cubic meters by 2010, and the gap will reach 60million cubic meters, of which the wood-based panel industry accounts for a considerable proportion of consumption, so the wood-based panel industry will increase by 3.5% Sensor of metal tensile testing machine: the quality of the sensor determines the force measuring stability of the testing machine, and the production efficiency is of great significance. As the key equipment of wood-based panel production, the hot press directly determines the production efficiency and product quality, and the performance of the hot press largely depends on the quality of its control system. In view of the problems that the existing hot press adopts relay contact control, which makes the control circuit of the press more complex, too many contacts and high failure rate, it is proposed to adopt PLC control in the hot press control system, which can omit some relays and locking contacts, simplify the control circuit and improve the reliability of the equipment. The PLC selects Siemens' 224cpu with a unimat 8di8do module behind it

1. Basic working principle

experimental hot press is one of the laboratory equipment in wood processing industry, scientific research institutions, colleges and universities, and can be used for hot pressing experiments of fiberboard, particleboard, plywood, surface decorative board, plastic board, etc. Except for the heating system, its working characteristics and structure are basically the same as that of the production type hot press. Figure 1 is the structure diagram of the hot press studied in this paper

the upper pressing plate 2 of the hot press is fixed. During normal operation, by controlling the plunger cylinder at the bottom of the press, the plunger 5 drives the lower pressing plate 4 to move upward to compact the slab; After the hot pressing treatment, the plunger 5 drives the lower pressing plate 4 to move downward and prepare for the next work after it is in place. According to the requirements of wood-based panel production process, in the working process of the press, the key is position control and pressure control. The system adjusts the speed through the proportional flow valve to realize position control

2. The design idea of PLC control system

first of all, it is necessary to meet the reliability of equipment in production. Due to the large number of components in the control part of the original equipment and the complex control lines, it is very difficult to troubleshoot. Therefore, PLC control can be considered for the control part of the lifting and lowering of the oil cylinder of the hot press. Under the condition of meeting the requirements, the input points and output points should be minimized to improve the reliability of the overall equipment; In addition, considering the equipment overhaul, maintenance and trial production of new board types, manual and automatic transfer switches need to be added to the control circuit; During maintenance, in order to prevent the raised pressing plate from displacement due to misoperation, a protection switch is installed. When the switch is placed in the protection state, even if misoperation occurs, the pressing plate will not move down due to electrical interlock. Based on the above design ideas, according to the work flow of the press, 17 input points and 14 output points are determined, a total of 31 points, using Siemens C40P product (this type of product has 24 input points and 16 output points) ez3

combined with the characteristics of this series of presses, the control circuit is designed and the control program is compiled; See Table 1 for the address of input and output quantities. Table 1 address of each input and output of plywood hot press

3, working principle and control process

take the fast veneer press as an example. This series of hot press is equipped with 4 oil cylinders, which are placed on top. The hydraulic oil circuit needs to be controlled by 6 solenoid valves. Due to the different specifications of the designed hot press, the power of the oil pump motor ranges from 10 to 22 kW. In order to reduce the starting current of the motor, it is designed as Y/△ starting. The plywood slab is loaded by a trolley, and the load-bearing part of the trolley can move in one direction. When the trolley exits, the slab will automatically slide on the pressing plate. The trolley drive motor is controlled by the frequency converter, which can realize the trolley fast forward, formulate relevant policies, and slow out

there are 6 solenoid valves controlling the oil cylinder, of which 1 1dt is the main oil inlet valve; The upper and lower oil circuits of each two oil cylinders are connected in parallel, and are divided into two groups. Each group has one upper oil inlet valve 3DT, 5DT, one lower oil inlet valve 2DT, 4dt, and one main oil return valve 6DT

oil is fed into the lower part of the oil cylinder, and the plunger moves up; The upper part of it feeds oil and the plunger moves down. That is, when 1dt, 2DT, 4dt work, the pressure plate rises, 1dt, 3DT, 5DT work, the pressure plate falls and pressurizes; When 6DT is working, the oil cylinder is unloaded. The hydraulic oil pump is driven by a three-phase AC asynchronous motor. In order to reduce the starting current, it needs to reduce the voltage. It is started in Y/△ mode, and the conversion time is 2 ~ 5 s. When the oil pump works normally for 3S, the pressing plate stops rising after it rises to the position (set the upper limit switch); At this time, the slab loading trolley quickly enters. After reaching the set position, the trolley unloads the slab and starts to retreat. It stops retreating after touching the retreat limit switch

at the same time that the trolley unloads and retreats, the pressure plate begins to fall. When it touches the lower limit switch, stop falling, start maintaining pressure and timing. With the increase of oil pressure, the pressure between the moving and fixed pressure plates increases. When the set upper limit pressure is reached, the upper limit switch of the electric contact pressure gauge is disconnected and the pressurization is stopped. The pressure required for hot pressing is automatically controlled by each group of solenoid valves to maintain the pressure until the end of hot pressing, and the unloading begins. After 3 s, the pressing plate rises. The unloading is completed manually

for the sake of safety, install a change-over switch in the control circuit, and add a protective device in the press rising control circuit. When the pressing plate rises in place, manually close this switch, so that the moving pressing plate will not fall and hurt people due to misoperation during equipment maintenance. At the same time, an overpressure protection switch is added to the pressurization and pressure maintaining control circuit to prevent the oil pressure from continuing to pressurize after reaching the upper pressure limit. In case of overpressure, the switch will be automatically disconnected, the solenoid valve will be powered off and the pressurization will be stopped. When the pressure drops to the allowable value, the switch is closed again and the system control returns to normal