1、 General introduction of electrohydraulic forming machine Electrohydraulic forming (EHF) is a kind of forming method which uses the high energy shock wave produced by the high current pulse discharge in the liquid. Because water is often used as medium to transfer energy, it is also called electrohydraulic forming. Compared with explosive forming, electro-hydraulic forming has the advantages of stable forming process, easy energy control, convenient operation, high productivity, and easy to realize mechanized automatic production. However, the electro-hydraulic forming equipment is complex, and its processing capacity is limited by the capacity of the equipment. Therefore, at present, it is only limited to the small and medium-sized batch production of small and medium-sized parts (below Φ 400mm). The electro-hydraulic forming method can be used for sheet and tube stamping, including drawing, bulging, shaping, stamping, punching, etc. ■ PLC computer control, constant current charging; ■ desktop and mobile models are optional;

■ double display of digital and pointer meter of electrohydraulic forming voltage; adjustable between 450V and 4000V (65 series 6500v);

■ the electric capacity can be switched, and the capacity is displayed;

■ electro hydraulic forming output counting function;

■ output pulse current display function

■ multiple safety protection functions.

2、 Ehf20 system composition of electrohydraulic forming machine 2.1 control cabinet The control cabinet includes cabinet, operation panel, charge and discharge control circuit, etc. The energy storage capacitor cabinet mainly includes pulse capacitors, transformers and vacuum switches. It is equipped with power switch, pause, charge, discharge, reset button and working voltage setting knob. It is equipped with voltmeter and various indicator lights to display the working state information transmission and display methods of the equipment, including instrument display, acoustic information transmission, tactile information transmission, symbol transmission, etc. Control technology, including machine control device, instrument control device, keyboard technology, etc. Safety assurance technology, including machine safety device, human error prevention, accident control method, rescue method, safety measures, etc. 2.2 energy storage capacitor cabinet The charging circuit is an important part of the electro-hydraulic forming machine. It must charge the energy storage capacitor reliably and efficiently. The charging circuit includes the first level DC power supply, the second level switch charging power supply, step-up transformer, rectifier circuit and corresponding protection circuit. The function of the charging circuit is to transform the alternating current into the energy in the energy storage capacitor after boosting and rectifying. This circuit consists of the first stage DC power supply, the second stage half bridge inverter circuit, the high voltage step-up transformer, the high voltage and high current rectifier silicon pile, the current limiting resistor, the energy storage capacitor and the sampling resistor. The working process of the charging circuit is the incoming AC, through the rectifier bridge and filter capacitor, the left and right DC voltage is obtained. This voltage is the input of the second half bridge inverter circuit, the second inverter circuit is the input voltage pulse of the transformer, the high-voltage transformer raises the electric voltage to the charging voltage, after the rectification, the capacitor is charged through the current limiting resistor. The sampling voltage on the sampling resistor is sent to the comparison circuit board for comparison with the set reference voltage, and the charging stops when the preset charging voltage is reached. Display and setting: The output voltage value is adjusted by the multi turn precision potentiometer, and the working voltage and current value are displayed by the digital display meter. The fault indication is indicated by the fault indicator light. Connector: The output high voltage is connected by high voltage connector, which is safe and reliable. Main features of energy storage capacitor: ·Low power consumption, suitable for high power, high current, high voltage, high surge applications; ·With the best capacity and volume performance ratio; ·Small change with temperature, long service life; ·The peak reverse voltage is the highest; ·High energy storage, high pulse current resistance; ·Good self recovery and stable performance; ·Low inductance, low ESR; ·The shell material is stainless steel or cold-rolled plate, which is easy to install. 2.3 electrohydraulic forming part The electro-hydraulic forming part includes electrode water tank and die, which can be customized according to different user needs. 3、 Features of electrohydraulic forming process: Principle of electrohydraulic forming The basic circuit of the electro-hydraulic forming device is shown in the figure below. The device is mainly composed of charging circuit and discharging circuit: 1. Charging circuit, which includes step-up transformer, rectifier and charging electricity; 2. Discharge circuit, which includes capacitor, auxiliary switch and electrode.

There are two forms of electric energy release in electrohydraulic forming, namely gap discharge and resistance exploding wire discharge. As shown in the figure above, the electrodes are connected with fine wire. When the capacitor is discharged, the strong pulse current will make the wire melt rapidly and generate high-pressure gas. Shock wave will be formed in the medium to make the metal blank stick to the mold, which is also called electric explosion forming. The results show that the energy conversion rate is high, the skin shape effect is larger and the distance between the two electrodes is larger. Electrohydraulic forming device Electrohydraulic forming can be divided into open forming and closed forming. In general, the energy utilization rate of open forming is only 10% ~ 20%, and that of face closed forming is up to 30%. The electrodes used in electrohydraulic forming can be divided into the opposite type, coaxial type, parallel type and movable type, etc. the opposite type and coaxial type are commonly used in production. The structure of the opposite electrode is simple and the insulating material is easy to solve, but the inherent inductance of the electrode is large. The intrinsic inductance of coaxial electrode is small in forming efficiency quotient, but the electrode structure is complex, so it has higher requirements for insulating materials. The parallel electrode is easy to adjust the distance between the electrode and the blank, but when discharging, it is affected by the transverse action of dielectric pressure and electromagnetic force, so it is necessary to pay attention to the structural strength. The movable electrode of the movable electric stage is placed in the air medium, while the fixed electrode is not in the liquid medium. The movable electrode is close to the fixed electrode by mechanical action. When the distance between the two electrodes is reduced to a certain value, the discharge phenomenon occurs. Therefore, the auxiliary gap in the discharge circuit can be eliminated and there is no insulation problem. However, due to the difference of the gap distance between each discharge, the instability of pressure and pressure distribution is caused, which affects the forming quality from the surface. The electro-hydraulic forming device is generally composed of water tank, discharge electrode and die. The shell and upper shell of water tank shall have sufficient strength. In order to ensure the accuracy of die sticking, the air in the die cavity should be removed before discharging, so the vacuum pumping system is often attached to the forming device.