The principle and solution of the sliding block return stroke of the four-column hydraulic press

The principle and solution of the sliding block return stroke of the four-column Hydraulic Press:

The slider of the four-column hydraulic press cannot return and the speed slows down. Let us first understand the operating principle of the lower slider:

Quickly descend, the electromagnet is energized, the pilot valve and the upper cylinder main reversing valve intervene in the left position of the system, the hydraulic control check valve is opened, and the upper hydraulic cylinder descends quickly. At this time, the oil flow in the system is as follows

oil inlet: hydraulic pump-sequence valve-upper cylinder reversing valve-one-way valve-upper hydraulic cylinder upper cavity

oil return line: upper hydraulic cylinder lower cavity-hydraulic control check valve-upper cylinder reversing valve-off-duty reversing valve-fuel tank

The upper slider quickly drops under the effect of its own weight. Because the flow of the hydraulic pump is small, the oil in the oil tank also flows into the upper cavity of the upper hydraulic cylinder through the hydraulic one-way valve.

Slow pressurization starts when the upper sliding block contacts the workpiece. At this time, the pressure in the upper cavity of the upper hydraulic cylinder rises, the hydraulic control check valve is closed, and the pressurization speed is determined by the flow of the hydraulic pump. The oil activity status and rapid downward movement The same time.

Hold pressure delay. When the pressure in the system rises to the effect of the pressure relay, an electric signal is announced and the solenoid is de-energized, the pilot valve and the upper cylinder reversing valve are in the neutral position, and the system enters the pressure holding at this moment. The pressure holding time is controlled by the time relay in the electrical control circuit and can be adjusted within 0min-24min. Except that the hydraulic pump is unloaded at a lower pressure, there is no oil activity in the system when maintaining pressure. The hydraulic pump unloading oil circuit is as follows

hydraulic pump-sequence valve-commercial cylinder reversing valve-lower hydraulic cylinder reversing valve-fuel tank

Quickly come back, after the time relay is delayed, the pressure is maintained, the electromagnet is energized, the pilot valve is inserted into the system in the right position, and the pressure relief valve makes the upper hydraulic cylinder reversing valve also connected in the system in the right position. At this time, the hydraulic control check valve is opened, and the upper hydraulic cylinder quickly returns.

Stop in place. When the upper sliding block rises until the stopper hits the original position travel switch, the electromagnet is de-energized, and both the pilot valve and the upper hydraulic cylinder reversing valve are in the neutral position. At this time, the upper hydraulic cylinder stops moving. The hydraulic pump writes unloading at a lower pressure.

Four-column all-round hydraulic press slide block return stroke error treatment:

Because the cylinder block, swash plate, plunger, sliding shoe, oil distribution plate and other parts of the plunger pump of the four-column all-round hydraulic press are worn, the internal leakage of the pump is severe, and the volumetric power decreases, so that the pump output flow cannot reach the set value.

Sweeping method: Modify all parts to ensure that the plunger slides sensitively in the cylinder hole, and the cooperation gap should be ≤0.06mm. The spherical surface of the shoe cooperates well with the plunger ball, the direction of rolling is sensitive, and the hole in the center of the shoe is kept unblocked. Eliminate burrs on the conflicting surface of the shoe surface and the swash plate.

The servo spool valve is worn and the gap is too large, causing the pressure compensation variable organization of the plunger pump to fail.

Cleaning method: The gap between the piston of the variable organization and the servo slide valve should be corrected to ensure that the gap is less than or equal to 0.008mm.

The treatment of the hydraulic slide block unable to return:

First check whether the return solenoid valve is stuck. Cleaning method: The return trip plug-in controls the pilot solenoid valve without operation. At this moment, the system pressure is very high. Check the solenoid valve. Look again at the support valve pilot high pressure relief valve pressure is too low.

Cleaning method: Check whether the pressure is too low, check the filling valve, and then check the support oil discharge plug-in block, cleaning method: whether the valve is blocked, whether there is debris on the annular contact surface of the valve core and the valve sleeve, and whether the center hole Blocked.

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