Research On The Pressure-relief Characteristics Of0.6MN Pump-controlled Press System

In practical production, oil hydraulic press discharging pressure too fast tends to leadto pressure impact and trigger pipeline and the press-frame vibration, releasing pressuretoo slow will extend the equipment cycle and reduce the production efficiency. Therefore,seeking reasonable pressure-relief method to achieve steady and rapid unloading is ofgreat significance.In this paper, pump-controlled hydraulic press system was mainly researched, inorder to reduce pressure impact and shorten the unloading cycle, reasonable variablepump rate change rule and unloading time have been proposed. In addition, pressureimpact mechanism was analyzed from the viewpoint of power flowBased on detailed analysis of the main cylinder pressure-relief process, functionrelationship of energy storage and the main cylinder pressure and function relationship ofthe main cylinder pressure and variable pump flow were deduced, furthermore, functionrelationship between energy storage and variable pump flow was established. A curve ofvariable pump flow rate has been proposed, based on the evaluation criterion onunloading characteristics, a method for determining of unloading cycle was put forward.in order to understand the relief process from the power flow point, a model ofpump-controlled hydraulic system power bond graph has been built and the energy flowlaw of each key element was detailly analyzed. AMESim model of the entire system wasbuilt, by simulating and analyzing of the pressure and speed response characteristics ofdifferent relief curves, the advantages of the derived curve has been pointed out. Inaddition, the pressure-relief characteristics influencing factors and the pressure-reliefcharacteristics of fast forging condition also have been analyzed.On the basis of theory and simulation analysis, experiment platform of0.6MNpump-controlled hydraulic press was built. The rationality of the theory unloading curvewas verified by comparative analysis of pressure of master cylinder and the main pumplow-pressure pipeline pressure response under different relief curves.