Vertical Pull Bed Master Cylinder Troubleshooting and Repair

Vertical pull-up bed is mainly used to pull flower keyholes and various geometric inner holes, due to high production efficiency, quality stability is widely used in the processing and manufacturing of mechanical parts. It is mainly composed of bed body, bed bench, main slip board, main cylinder, servo variable plunger pump and all kinds of hydraulic valves, etc. , is based on liquid pressure-powered mechanical processing equipment.

Hydraulic equipment structure is simpler than mechanical equipment and easy to repair, but because of the hydraulic transmission failure of more related factors, therefore, the cause of the fault is relatively difficult to judge. The vertical pull bed master cylinder failure described in this paper is a typical fault. The phenomenon, diagnosis, and repair process for this fault are described below.

How the hydraulic system works.

Press the hydraulic start press new, the main oil pump and its built-in gear pump began to rotate together, at this time the hydraulic valve YV1, YV2, YV3, YV4 and YV5 are all power-off state, the main oil pump eccentricity is 0, no pressure oil output, gear pump has pressure oil output. The pressure oil output of the gear pump is acted on the zero valve by YV1, the zero valve is connected, and the main oil pump is in the discharge state. The pressure oil output of the gear pump is the servo variable mechanism of the main oil pump (consisting of zero-position plunger, fast plunger, slow plunger, return-to-fast plunger, return-slow plunger, reset plunger, servo spool, servo cylinder, YV1, YV2, YV3 and YV4) to control the operation of the servo cylinder, pushing the main oil pump to produce eccentricity. Through the combination of hydraulic valves YA1, YV2, YV3 and YV4 power-off, the eccentricity, eccentric direction and pressure oil discharge direction of the main pump are controlled, and the main cylinder is operated, returned and fast and slow forward.

Main skateboarder fast: press the main skateboarder fast press new, YA1, YV5 electricity. YA1 electricity, the main oil pump in the maximum working eccentricity, discharge oil is cut off, the main oil pump output pressure oil from the working direction into the differential combination valve CSY-717 in the one-way valve, injected into the cylinder upper cavity (with rod cavity); Electricity, sequence valve work, cylinder cavity return oil flow through the sequence valve, part of the main oil pump inhalation re-injected into the cylinder upper cavity, excess oil by recharging the valve - back pressure valve back to the tank, piston down, the main slip plate began to work fast.

Main skateboarders are slow: YA1, YV3 and YV5 get electricity. YA1, YV3 electricity, the main oil pump in the smallest working eccentricity, discharge oil is cut off, YV5 electricity, sequence valve work, the in return oil flow and the same fast.

Main slip board back fast: YA1, YV2 electricity, the main oil pump in the maximum return eccentricity, discharge oil flow is cut off, the main oil pump output pressure oil from the return direction into the balance valve PH-300 in the one-way valve - cylinder cavity (no rod cavity). The return-through differential combination valve CSY-717 in the cylinder upper cavity (the taper valve is opened by pressure oil) and the pressure into the lower cavity meet to achieve cylinder differential, the cylinder returns quickly.

Main slip board back slow: YA1, YV4 electricity, the main oil pump in the minimum return eccentricity, discharge oil flow is cut off, the in return oil flow and return fast the same.

The phenomenon of the fault.

Fault phenomenon description: according to the work cycle press new, the main slip plate downward pull-down processing, but the main slip plate down to the puller and the workmanware contact, the main slip plate will stop moving, the main oil pump work less sound.

Fault phenomenon: The main skateboard does not have slow travel.

Troubleshooting.

Hit the adjustment position (no puller remover), tap the main skateboard to return to press the button, return to normal. Tap the main skateboard to work button, drop normally, but stop when you touch the work piece.

Preliminary judgment: may be the oil pump work eccentric abnormal, the main pump discharge load and the main oil pump low working pressure and other reasons.

(1) According to the above judgment first do the following check: (1) check the main oil pump eccentricity. Repeated return and work action, eccentric needle shows that the main oil pump eccentric normal, slow limit screw position is normal, no loose. (2) Check the YA1 hydraulic valve. Check the control of the main oil pump work eccentric electromagnetic change valve YA1, electromagnet, power loss is normal, spring intact, valve core activity is normal, can be normal change. (3) Check the zero valve. The pressure nut of the zero-position valve is not loose, the spring is intact, the valve core activity, with the gap is normal, there is no possibility of oil leakage. (4) Check the system pressure.

The main skateboard returns, removes the puller, presses the main slip plate down to press the button, ready to observe the in-pass pressure. But the main skateboard suddenly fell quickly and made a loud bang. Press the emergency stop button, shut down the hydraulic system, check the cylinders, pumps, oil lines and the whole machine no signs of damage, cylinders, oil lines do not leak. Re-start the hydraulic system, short press the main slip board rise press new, the main skateboard rise normally, press the main slip plate drop press new, the main skateboard quickly fell to the bottom of the cylinder, making a impact sound. Continue to hold the main slip plate down press new, check the main oil pump operating pressure, pressure is normal, loosen or tighten the main oil pump work safety valve nut, pressure is adjustable, re-adjust the pressure and tighten the locking nut.

Check results: main oil pump eccentricity, YV1 hydraulic valve, zero valve and system operating pressure are normal, the cylinder drop is not normal. The above check corrects some of the causes of the fault, and also identifies the phenomenon of the fault.

(2) Fault phenomenon analysis. The rapid drop of the cylinder may be related to the balancing valve (consisting of a combination of sequential and check valves) mounted on the oil path mounted in the lower cavity of the cylinder. It supports the quality of the main skateboard to prevent the main skateboard from falling. When the main slip plate rises, the pressure oil enters the lower cavity of the cylinder through the check valve in the balance valve. Open the sequential valve return when the lower cavity return pressure of the cylinder reaches the sequential valve set pressure when the main slip plate is down. Proper pressure balances self-weight and the load does not drop it. High pressure increases the drag of the main slip board down, increases the load, and increases the system loss. When the pressure is low, when the main slip plate goes down, there will be an overstrip phenomenon, affecting normal cutting. From the front operation can be seen after the main skateboard stop, there is no sliding phenomenon, indicating that the balance valve can play the role of supporting the main skateboard. To rule out possible effects of the balancing valve, check as follows.

(3) Check the balance valve. Start the hydraulic system, the main slide board rise to a higher position, the main slide board does not slide phenomenon. Lower the sequential valve pressure until the main slide starts to slide, increase the sequential valve pressure, the main slip plate stops sliding, indicating that the balance valve in the sequential valve and the check valve are not a problem.

(4) Comprehensive analysis. After the above inspection, the fault phenomenon can be summed up as: the main slip plate with knife cutting can not work in the infusion; That is, when there is a load, the forward speed is zero, and when there is no load, the falling speed is very fast.

When there is a load, the supply speed is zero: the hydraulic system operating pressure, the main oil pump eccentricity and the zero valve are normal.

Falling speed is very fast when there is no load: indicates that the hydraulic system has operating pressure, the main oil pump has eccentric, zero valve and balance valve is working properly. The previous checks also show that the working pressure, oil pump eccentricity, zero valve switching and balance valve operation are normal.

After the above inspection and analysis, the equipment fault can be corrected is caused by the main oil pump, the working relief valve, the sequence valve, the zero valve and the YA1 solenoid valve. Analysis from the fault phenomenon itself can be seen, if the sequence valve, check valve damage, the main slip plate can only slide at a certain speed, it is not possible to instant rapidly fall and hit the bottom of the cylinder, because the return of oil takes time, the main slip plate can fall to indicate that there is working pressure oil into the cylinder upper cavity, falling fast, indicating that the return oil is very fast, so much oil immediately discharged, where these oils go? From the hydraulic chart can be seen that the system leakage, cylinder leakage is not likely to make a large number of hydraulic oil under the cylinder cavity quickly empty, on-site inspection did not find oil leakage or cylinder phenomenon.

Pull bed main slip plate cylinder is vertically installed, the rod cavity is the upper cavity, the piston is installed under the piston rod, if the piston is separated from the piston rod, when the main slide returns, the lower end of the piston is affected by upward pressure oil, the piston and piston rod are in the normal assembly position, can work properly. When the main slip plate is stationary, the piston is subjected to forces up and down in the opposite direction of equal size, and the piston does not detach from the piston rod. When the main slip plate works, in the moment of pressure oil action, the main slip plate and piston rod maintain inertia, the upper part of the piston under the action of pressure oil quickly down from the piston rod, the original lower cavity oil through the piston hole into the cylinder upper cavity, the piston under the action of the upper pressure oil immediately fell to the bottom of the cylinder, lost the lower cavity pressure oil support of the main slip plate and piston rod quickly fell to the bottom of the cylinder and made a crash sound. In order to verify the correctness of the above analysis, the following operations are carried out: start the hydraulic system, the main slip plate will rise a certain height (at least 300 to 400 mm from the bottom of the cylinder, to exceed the thickness of the piston, otherwise the piston rod and piston can not be dislocated, can not observe the following phenomenon), close the sequence valve, that is, the lower cavity of the cylinder circuit closed, press the main slip plate drop press new, the main slip plate stationary. The original pressure value of the recovery sequence valve, press the main skateboard to drop press the new, the main slip board is still falling rapidly, indicating that there is a problem inside the cylinder, the internal leakage is very large.

The fault is fixed.

Remove components such as the main slip plate, ter pipe, remove the main cylinder, remove the cylinder and find the nut damage to the fastening piston and the piston rod, which can be easily separated. Refit the installation and do anti-loose treatment, reinstall adjustment test drive, the main skateboard work trip returned to normal.

It is important to note that when repairing this vertically mounted cylinder, be sure to lower the cylinder to the bottom of the cylinder to avoid equipment or personal accidents.

Conclusion.

The key to this fault judgment is the rapid fall of the cylinder, the lower cavity must have a large amount of fluid quickly discharged, how to discharge? Where's the queue? For such a large-scale equipment, we must clear the phenomenon of failure, carefully analyze the hydraulic working principle, fault phenomenon and combined with the equipment structure, the cause of the various possible causes of the phenomenon of failure, first peripheral and then internal, one by one exclusion, to find the real cause. The cylinder failure described in this article also occurs in other equipment, because the cylinder installation location is different, the fault phenomenon will be different, so the fault repair process is based on the analysis of the equipment itself.