The metal products industry is inseparable from the material testing machine, and the users of the product enterprises are inseparable from the testing machine. However, the quality objection caused by the failure of the testing machine is not uncommon. Material testing machines often fail. The following is the cause analysis of common failures:

Common faults: during the loading process of the testing machine, the body vibrates, the pointer rotates unsteadily, and the value cannot be read accurately:

First eliminate the vibration source that may cause resonance around the testing machine, and then observe whether the installation foundation of the machine is firm, and check whether the motor fails. After these faults are eliminated, the pointer is still unstable, so it is necessary to consider whether there is air in the oil circuit system.

The method is: start the oil pump, close the oil return valve, make the main piston rise a certain height, and then open the oil return valve to make the oil flow back to the oil tank from the main oil cylinder of the oil pump through the oil return valve. After circulating for a period of time, the air in the main oil cylinder can be exhausted. Then unscrew the screw of the exhaust hole of the oil collecting tank and tighten it when the emerging oil does not contain bubbles.

In addition, you can also remove the high-pressure oil pipe of the oil pump and start the motor to completely eliminate the air in the oil pump. For the testing machine used for a long time, the oil should be changed regularly and the gear rod, gear, pointer and thread wheel of the force measuring part should be cleaned. (it should be noted here that each time the reel is cleaned, the diameter of the replaced chord should meet the requirements, and the direction and number of turns on the reel should be appropriate.) Dirty oil sometimes changes the pressure balance of the oil delivery valve due to debris blockage, resulting in uneven oil circulation. The length of the two V-belts connecting the oil pump is inconsistent, and the plunger in the oil pump does not work normally or the clearance of the seven groups of oil distribution valves is different, which will cause the vibration of the testing machine.

Common faults: poor sensitivity of dial pointer, midway stop after unloading, or constant change of zero position:

1. The pulley and its track on the toothed rod are too dusty and rusted. At this time, it needs to be removed and cleaned, plus a little watch oil. The pointer rotating shaft is dirty and should be cleaned.

2. If there is contact between the toothed bar pressing plate and the toothed bar, it should be loosened.

3. The oil return condition of the buffer is poor, which should be adjusted or cleaned. (it refers to that the curve is blocked)

4. The belt on the force measuring piston falls off or is too loose (so that the piston cannot run at a uniform speed). If the friction force of the force measuring piston increases or gets stuck in the oil cylinder, apply chromium oxide grinding paste to grind it until it is normal.

5. There are obstacles in the lifting process of the pendulum, or the pendulum shaft is too dirty or rusted, which makes the pointer return to zero and change greatly.

Common fault: when doing tensile test, the fracture of the sample is always broken on both sides. In this case, it is necessary to consider whether the installation of the main part of the testing machine is vertical first, eliminate this reason, and then eliminate it from the following three aspects.

1. If the jaw is not placed correctly during clamping, make the jaw symmetrically clamp the sample as required:

2. The jaw quality is poor, and the teeth are damaged, which not only affects the jaw misalignment, but also makes the sample slip during the test, making the yield point difficult to identify. Replace the jaw at this time.

3. The lifting guide wheel is not adjusted correctly, so that the upper and lower jaws are not concentric. An inspection rod shall be processed. After the upper and lower jaws are tightened, measure with a dial indicator based on two force columns until the adjustment is qualified.

Common faults: the pendulum position is abnormal, and the pendulum rod is not aligned vertically.

The main reason is that the viscosity of the oil is too large or the oil is too dirty. Troubleshooting: replace the oil with proper viscosity.

The force measuring piston rotates with great friction or does not rotate. Troubleshooting: check whether the testing machine is level and eliminate the fault of the force measuring piston.

There is unstable friction. Troubleshooting: clean the pendulum shaft bearing, gear rod, pointer and thread wheel, adjust the level of the testing machine, and reduce the unstable friction.

Common faults: abnormal hammer return, fast and slow:

Usually, turn the buffer to the proper position. However, if the oil hole of the buffer is blocked, or the steel ball of the buffer valve contacts the inlet with dirt or the gap is too large, the buffer will fail. The solution is to clean the buffer valve and adjust the clearance between the steel ball and the valve seat to about 0.5mm. Place the oil needle knob to reduce the gap between the oil needle and the valve body, and re list the marks of A.B.C mound. In addition, when the temperature has a great impact, the oil can be changed appropriately.

Common faults: the passive needle cannot stop at any position well, and it does not coincide with the main needle.

The troubleshooting method is to remove the dial glass, adjust the compression spring screw of the passive needle, and adjust the pointer to make it coincide with the main needle.

Common faults: when loading, the oil circuit system leaks oil seriously or the oil pipe breaks:

Check whether the joint of the oil circuit system is tightened. If it is necessary to replace the gasket, replace it in time. If the oil pipe is broken, the oil pipe with higher strength needs to be replaced. In addition, observe whether the piston of oil delivery valve and overflow valve is dead or installed reversely.