Technical transformation of hydraulic system of Y32- 200T hydraulic press

The structure of Y32-200T four-column hydraulic press machine is shown in Figure 1. Its main technical parameters: nominal force 2000kN; ejection force 240kN; slider stroke 800mm; ejection stroke 200mm; table effective area (1000×900) mm; slider empty stroke speed 90mm/s; slider working stroke speed 7～14mm / s; the return speed of the slider is 60mm/s; the maximum distance between the slider and the table is 1000mm, and the working fluid pressure is 25MPa.

Figure 1——Schematic diagram of multi-directional die forging hydraulic press machine

According to the transformation requirements, two blank holding hydraulic devices are added to the original foundation. The blank holding device is installed under the upper beam. The main technical parameters are as follows: blank holding force 500kN; blank holder maximum working stroke 200mm; blank holder working Stroke speed 7～14mm/s; slider return speed 40mm/s; the maximum distance between the blank holder and the table is 850mm.

Taking into consideration the effective area of the original hydraulic press machine working table and the forming force range of the multi-directional die forging for testing, the technical parameters of the one-sided side forming device are as follows: nominal force 1000kN; slider working stroke 300mm; slider working stroke speed 7～14mm/s; the center height of the lateral forming cylinder is 550mm.

(1) Overview of hydraulic cylinder structure design

The hydraulic cylinder structure design includes the type, size, and support method of the hydraulic cylinder. This is because the hydraulic cylinder is the actuator of the hydraulic press machine, the output power bears the load, and it is also a component that is easy to fail in the hydraulic press machine. Choosing the proper cylinder structure, specifications and support methods of the hydraulic cylinder can not only ensure the accurate action of the hydraulic cylinder, but also extend the service life of the hydraulic cylinder. When designing the hydraulic cylinder structure, the choice of its structural form generally depends on the support mode of the hydraulic cylinder on the hydraulic press machine, and the specifications and models of the hydraulic cylinder are calculated and determined according to the total working pressure of the hydraulic press machine.

(2) Structure design of blank holder

Due to the limitation of the main structure of the Y32-200T hydraulic press machine, the blank holder hydraulic cylinder cannot be fixedly installed on the upper beam, so we choose to install a 150mm thick steel plate on the movable beam, and process through holes on the steel plate. Together, the cylindrical surface of the outer wall of the hydraulic cylinder is installed in cooperation with the through hole in the steel plate. Because it is a small hydraulic press machine, the piston cylinder is used as the blank holder.

1) Calculation of the inner diameter of the blank holder. As known from formula ①, the inner diameter of the hydraulic cylinder is determined by the nominal pressure of the blank holder and the hydraulic fluid pressure of the hydraulic system. The nominal pressure F is 500kN, the hydraulic pressure P = 20MPa, and the calculated D1 is 180mm.

D1 = √4F / πP ①

2) Calculation of the piston diameter of the blank holder. The relationship between the piston diameter of the blank holder and its inner diameter is shown in formula ②, where the quasi is related to the working pressure P. When the working pressure P is greater than or equal to 20 MPa, the quasi = 2.3, so the piston diameter d = 0.75D1, d is rounded to 135mm.

d = D√Φ-1 / φ ②

3) Calculation of the outer diameter of the blank holder. It is known that the inner diameter of the hydraulic cylinder D1 = 55mm. Because the hydraulic cylinder material uses the 35th cylinder, the allowable stress of the material is σ = 200MPa, and the outer diameter of the hydraulic cylinder calculated by formula ③ is 210mm.

D2 = D1√σ / σ-√3P ③

4) Check the return force of the blank holder. The hydraulic cylinder needs to overcome its own gravity, friction and other factors when returning. The general return force is 10% to 20% of the nominal pressure. The return force of the blank holder calculated by formula ④ is 247kN, which meets the design requirements.

F1 = π (D1²-d²) P / 4 ④

(5) Determination of other dimensions of blank holder. Wall thickness: δ = (D2-D1) / 2 = 15mm, cylinder bottom thickness: t1 = (1.5～2) δ, take t1 = 30mm, flange thickness: t2 = (1.5～2) δ, take t2 = 30mm .

(3) Structural design of the lateral forming cylinder

The lateral forming cylinder adopts the symmetrical setting of the piston cylinder and adopts the tie rod to support the connection, the cylinder body is fixed on the lateral support base, and the lateral support base is connected with the hydraulic press machine base. The nominal pressure of the lateral forming cylinder is 1000kN, and the hydraulic pressure is 25MPa. The relevant technical parameters of the lateral forming cylinder can be obtained from the above hydraulic cylinder parameter calculation formula. The technical parameters of the blank holder hydraulic cylinder and the lateral forming cylinder are shown in Table 1.

Table 1——Technical parameters of blank holder and side forming cylinder

The design of the hydraulic system includes two parts, one is the hydraulic system design in the vertical direction composed of the blank holding cylinder and the main cylinder and the ejecting cylinder, and the other is the hydraulic system design of the lateral forming hydraulic cylinder.

(1) Hydraulic circuit design of double-acting hydraulic press machine

Due to consideration of retaining the hydraulic system of the original Y32-200T hydraulic press machine, two hydraulic circuits of blank holder cylinders are added to the original system to form the hydraulic circuit of the double-acting hydraulic press machine.

The working process of the hydraulic press machine in the vertical direction is as follows: The empty stroke of the master cylinder is quickly downward. When the blank holder slides close to the blank, the master cylinder descends slowly. The blank holder provides variable blank holder force and the blank is completed. After that, the system releases the pressure and the main cylinder drives the movable beam back, which rises to a certain distance after the blank holder returns, and then ejects the cylinder to eject the product, completing a working cycle.

1.4.7. Filter 2. Motor 3. Cooler 5. Variable piston pump 6.8.21. Check valve

9.22. Overflow valve 10.11.12.13.15.18.19. Directional valve 14.16.23.24. Filling valve 17. Hydraulic control check valve 20. Balance valve

Figure 2——Vertical hydraulic circuit of hydraulic press machine

It can be seen from Figure 2 that the hydraulic system uses an electro-hydraulic proportional control system and PLC programming control. According to the displacement signal set by the system, it sends out corresponding commands to control the sequential actions of each actuator in the vertical direction. The hydraulic pump is a single variable plunger pump, which also satisfies the working conditions of the low-pressure rapid ejection cylinder and the high-pressure slow speed of the main cylinder and blank holder cylinder, saving system energy. In order to reduce the vibration and impact of the system during commutation, an overflow valve 22 is added for overflow and pressure relief. The reversing and stopping of the blank holding device are controlled by the two central functions of valve 11 and valve 12, which are O-type three-position four-way reversing valves. When filling.

(2) Design of hydraulic system of lateral forming hydraulic cylinder

The lateral forming device is mainly used for the forming of multi-directional hot die forging. Because in the multi-directional hot die forging process, the temperature of the blank has a great influence on the force during forming and the flow line of the metal product after forming, so when forming the hot die forging product, the lateral hydraulic system is required to be able to Quick work to complete the extrusion of the blank, and must have the function of holding pressure. At the same time, due to the different shapes of the left and right sides of the hot die forging parts, the required force and forming time are also different, so the hydraulic system is required to be able to drive the left and right cylinders independently, and the pressure is opposite, Adjustable speed.

The working process of the hydraulic press machine in the horizontal direction is as follows: the left and right hydraulic cylinders are quickly advanced-extruded parts-holding pressure-releasing pressure-the hydraulic cylinders on both sides are retracted simultaneously.

Figure 3 is the hydraulic system diagram of the lateral forming device. It can be seen from the figure that the left and right hydraulic cylinders are independently driven by their variable pumps, and their speed can be adjusted by the flow of the variable pump; Limit the maximum pressure of the hydraulic system of the left and right cylinders; during the return stroke, in order to reduce the impact during commutation, relief valves 8 and 17 are installed on the return stroke respectively. The left and right cylinders can work independently and release pressure, or they can be connected by switching the directional valves 21 and 22 to achieve synchronization of work and pressure relief.

1.11. Filter 4.13. Cooler 2.12. Variable piston pump

3.7.15.18. Check valve 6.8.16.17. Overflow valve 9.10.19.20.21.22. Solenoid directional valve

Figure 3——Lateral device hydraulic circuit

From the design of the hydraulic system, it can be seen that in the multi-directional die forging forming process of the hydraulic press machine, the following three forming processes can be selected according to the process requirements: first, the vertical direction is formed, then the horizontal direction, and finally the mold is opened up and down, left and right Ejection; second, the horizontal direction is formed first, and then the vertical direction is formed, and then the mold is ejected; third, the horizontal direction and the vertical direction are formed together, and the mold is ejected.

(1) According to the main technical parameters of the Y32-200 T hydraulic press machine, the technical parameters of the blank holder and lateral forming device are determined on the basis of maximum use of the original equipment.

(2) On this basis, select the type of the corresponding hydraulic cylinder and calculate its main specifications and model parameters.

(3) According to the requirements of working conditions, the hydraulic system diagram of the vertical molding direction and the hydraulic system diagram of the lateral molding direction are designed, and three process plans for multi-directional die forging are proposed.

After the overall transformation of the hydraulic press machine, it is applied to the actual multi-directional die forging hot forming of the connecting rod, which can meet the technological requirements of product forming, and the application range of the hydraulic press machine has been greatly improved.