Fast Based On Fast Switching Valve Presses The Hydraulic System

The CNC turret press is a kind of computer controlled flexible sheet punch processing equipments. In addition to the characters of traditional CNC turret press, the hydraulic CNC turret press has the characters of high stepping frequency, simple structure, easy maintenance, safety and reliability, It has been applied more and more extensively at home and abroad. Most of the CNC presses produced in our country are mechanical. There are few hydraulic CNC presses in our country. All the hydraulic systems were imported from foreign countries.Because of the high controlling precision and the fast dynamic response of the electrical-hydraulic servo valves, they are widely used in hydraulic control systems. But they have the disadvantages of the poor ability for anti-pollution, the huge waste of energy, the complexation of the controlling electric circuit and the high price. Because of the high flow resistance and the poor flowing ability, the spool valves can't meet the requirements for high velocity or huge hydraulic equipment.In order to overcome the disadvantages of servo valves and the spool valves, the fast hydraulic system controlled by the fast on-off valve is researched which uses the on-off valves as the pilot valves. They are used to control the opening and closing of the logic valves, thus they can control the pressure and the flow. So they can control the movement direction and the velocity of the piston. The fast hydraulic system studied in the paper is applied in the CNC turret press in our country for the first time.On the basis of the initial experiment systems in this paper, the advantages and the disadvantages between the two experiment systems have been compared and analyzed, and MATLAB WITH SIMULINK software has been used for the numerical simulation. On the basis of the artificial, the displacement curve, the velocity curve and the pressure curve of the oil crock are obtained. On the basis of simulation, the two experimental systems are studied. The results of the experiment and the simulation are compared. The suggestions to improve the system have been gotten.From the research of the experiment and the simulation, conclusions and suggestions are gotten:(1) The fast hydraulic system which uses fast on-off valve as the pilot valves to control the logic valve is an available system. The system is simple. It can meet the requirements under the condition without loads. The working stroke is 6mm. And the stepping frequency is 300times/minute.(2) In the original system because of the area between the piston and the piston pole is too small, the system pressure will rise when in the return stroke. And the reliever valve will open. The return velocity will reduce. So the working efficiency is low.(3) From the structure of the logic valve, as the poppet valve is sealed by a line touching, the service life should be tested.(4) In order to improve the system and its working function, a hydraulic controlled direction valve is connected in the main oil circuit to control the differential of the piston. Then the dimentions of the cylinder and the piston are reduced, improving the working properties.(5) If the opening of the logic valve is limited, the fast transformation function of the logic valve will be improved, and the returning time of the piston will be reduced. Then the working efficiency is improved too.The improved project is simulated. From the simulation results, the better characters have been gotten.