Troubleshooting Slow Return Speed of 315-Ton Hydraulic Press Hydraulic Cylinder
Troubleshooting Slow Return Speed of 315-Ton Hydraulic Press Hydraulic Cylinder
The hydraulic pump of the four-column hydraulic press is a fixed displacement pump, and the directional valve is a two-position four-way solenoid directional valve. The valve is placed in the return oil path of the hydraulic cylinder, creating a return speed control system. During the return of the hydraulic cylinder, hydraulic oil enters the rod chamber of the hydraulic cylinder through the check valve. The safety valve plays a role in maintaining constant pressure and overflow in the system. The malfunction observed in the hydraulic press system is a slow speed of the hydraulic cylinder with no significant return speed.
Upon inspection and debugging of the system, it was found that the hydraulic cylinder retracts quickly, and the operational actions are normal. However, during fast return, it is abnormal. Check the check valve to ensure its proper operation. When the hydraulic cylinder returns without a working load, and the system pressure is relatively low, the hydraulic pump's outlet flow enters the hydraulic cylinder through the rod chamber, requiring the hydraulic cylinder to have a higher speed. However, it was discovered that the return speed of the hydraulic cylinder is slow, and the system pressure remains high.
Upon disassembling the directional valve, it was found that the directional valve lacks elasticity and tilts, preventing the valve core from returning to its original position after power-off. As a result, the opening of the spool is too small to allow oil through the directional valve, saving oil for the system. Most of the pressure oil output by the hydraulic pump returns to the tank through the relief valve. At this point, the pressure in front of the valve switches to the set pressure of the safety valve, causing pressure to rise during the hydraulic cylinder's return.
The increased return resistance of the valve core may also be due to dust entering the clearances of the spool, making the movement of the spool difficult. The gap between the spool and the valve hole is too small, causing the valve to jam when the oil temperature rises. The seal resistance of the electromagnetic push rod is too high, causing deformation of the valve hole during the installation of the solenoid valve. Once the actual cause of the jamming is identified, the corresponding cleaning method becomes straightforward.
Since most of the pressure oil overflows into the fuel tank, there is relatively little oil in the rod chamber through the directional valve of the four-column hydraulic press. Therefore, the hydraulic cylinder does not have a significant return speed.
The solution to this type of four-column hydraulic press malfunction is that the spool cannot return to its original position due to the spring, and a qualified spring should be replaced. If the jamming is caused by poor accuracy and radial clamping occurs, the spool should be repaired or remade from scratch. The standard tolerance for the bitterness cone of a regular spool is 0.003-0.005mm. It is advisable to have a small taper on the spool and have its large end on the low-pressure chamber side, reducing the problem automatically, minimizing friction, and then reducing or avoiding warping clamping force.