Hydraulic buffer device of the hottest closed comp

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Abstract: This paper introduces the principle of closed double action extrusion forming, the structure of hydraulic buffer device, and analyzes the extrusion forming process, the working process of die buffer device and the working principle of hydraulic system

key words: closed forming; Compound motion forming; Cold extrusion forming; Hydraulic buffer; Hydraulic system

0 introduction

fast, direct, no cutting (i.e. net shape) or less cutting (i.e. near net shape) processing has always been the goal of the machinery industry. In recent years, with the rapid development of industry, especially the continuous development of automobile industry, higher requirements are put forward for the forming of complex shape parts and high-precision parts. Cold extrusion technology is undoubtedly the most effective way to solve the above problems. However, the traditional cold extrusion process can no longer meet the above requirements, so new cold extrusion technology came into being, such as closed forming, FCF process, compound forming, compound forming and so on. The application of these new processes and methods has better solved the direct, less and no cutting needs of industrial development for complex shape parts and high-precision parts. The application of these technologies not only solves the problem of forming quality, but also solves the problems of long process route and the need for softening and lubrication between processes in the traditional process, which not only ensures the processing quality, but also saves a lot of costs. Therefore, the application prospect is very optimistic. Closed compound extrusion is a widely used cold extrusion technology. The die with closed compound action extrusion forming technology is different from the traditional die structure, and the buffer device of the die is the key to the design of this kind of die

1 principle of closed double action extrusion forming

the so-called double action extrusion forming, that is, the cold extrusion forming process with two or more process actions at the same station, is called double action extrusion forming. According to whether the die cavity is closed or not, the double action extrusion can be divided into two states: closed double action extrusion and non closed double action extrusion. Because the closed double action extrusion process can obtain better forming quality, it has been widely used. Figure 1 shows the comparison between the traditional pier extrusion process and the closed compound extrusion process for drum shaped parts. Through comparison, it can be seen that using the traditional pier extrusion method will inevitably produce flash, as shown in Figure 1 (a), the value of the size will change according to the amount of material, thus affecting the drum shape: consumers have reason to believe that the value under the increasingly perfect service system and good service attitude, and: here represents a complex surface, which is generally guaranteed by the simple mixing of different plastic components such as molds in a combustion device, and no longer processed, This will directly affect the forming quality of formed parts. Figure 1 (b) shows the working process of closed compound extrusion forming. In the working process, the upper and lower dies are closed first, and then the lower die core moves upward axially to extrude the material. It can be seen that the dimension h shown in the figure is strictly controlled, thus ensuring the forming quality of complex surfaces

2 structure of hydraulic buffer device

figure constantly advancing towards the world's scientific and technological power. The closed and compound extrusion forming process of drum shaped parts shown in 1 (b) requires strong power to drive the lower die mandrel, which brings many difficulties to the design of presses and dies. The same principle, using the movement mode that the number of use can reach more than 50 times as shown in Figure 2, that is, the closed compound motion extrusion forming of parts can be realized on an ordinary press. As shown in Figure 2 (a), when the work starts, the upper and lower molds close as the slider of the press descends. Then, as the slider continues to descend, the upper and lower molds move together relative to the mandrel of the lower mold to complete the closed compound extrusion forming. In this design mode, the closing of the upper and lower molds and the extrusion of the mandrel on the blank material are all completed by the powerful power of the slider. Therefore, it can be directly carried out in ordinary hydraulic press and mechanical press. The problem to be solved is how to solve the buffer problem when the die moves relative to the mandrel. Because the hydraulic pressure has the function of automatic overload protection, the hydraulic buffer device can better solve this problem. Figure 2 (b) shows the condition of parts formed by closed and compound extrusion when there is too much or too little blank material. It can be seen that less material will directly affect the forming quality of parts. Therefore, appropriately increasing the material and leaving some machining allowance on the easy machining surface will not affect the forming quality

Figure 3 is the structural diagram of the hydraulic buffer device of the single cylinder buffer closing compound action extrusion forming die. It can be seen from the figure that the whole die is supported by a hydraulic piston cylinder. The lower mold base is actually a plunger. The lower mold is fixed on the lower mold base through the compression nut, and the lower mold mandrel is directly fixed on the lower mold. When there is a closed compound action extrusion forming process driven by the upper and lower mandrel, the upper and lower die bases should be equipped with buffer cylinders. Its structure is shown in Figure 4

3 working principle of hydraulic system

Figure 5 shows the hydraulic system schematic diagram of the single cylinder buffer closing compound action extrusion forming die buffer device. The system is composed of buffer hydraulic cylinder 7, accumulator 8, one-way sequence valve 6, auxiliary hydraulic pump 1, one-way valve 3, overflow valve 4, two position two-way solenoid valve 2 and safety valve 5. After the oil pump is started, the oil is unloaded through the two position two-way solenoid valve; After the work starts, the solenoid valve is energized, and the pressure oil is input into the hydraulic cylinder through the one-way valve. At the same time, the pressure oil in the accumulator is also input into the hydraulic cylinder through the one-way sequence valve to realize rapid oil charging and jack up the lower die. When the upper and lower dies go down, the pressure in the buffer hydraulic cylinder rises sharply, the check valve is closed, and the oil is discharged into the accumulator by opening the sequence valve

after the work is completed, as the slider rises, the pressure in the mold cavity is quickly released, and the oil in the accumulator immediately fills the hydraulic cylinder with oil through the one-way valve, and the lower mold is jacked up

4 conclusion

closed compound action extrusion forming is an advanced metal forming method in cold extrusion technology. The key is the design of die buffer mechanism, and the use of hydraulic buffer device is undoubtedly a preferred method. In the specific design, the larger plunger area should be selected as much as possible, so that the smaller working pressure of the hydraulic system can be selected, and the set pressure of the sequence valve can be selected according to the working pressure of the system. Generally, the set pressure of the sequence valve should be MPa higher than the working pressure of the system, and the set pressure of the safety valve should be greater than the pressure of the sequence valve; The capacity, minimum and maximum working pressure of the accumulator shall be carefully designed. For the closed forming die, high-precision guide sleeve and guide post should also be selected for guidance. (end)

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