What are the common faults of the universal testing machine?

What are the common faults of the universal testing machine?
The universal testing machine is a necessary equipment to control the quality of the product. How to troubleshoot and ensure the good operation of the machine during use, the operator should learn to find the problem and be able to eliminate it. The following are some personal opinions, I want to share with you.

Common failures of universal testing machine:

(1) The dial pointer has poor sensitivity and stops halfway after unloading, or the zero position often changes. There are many reasons for this phenomenon.

1. Excessive dust and rust on the pulley and its track on the gear rod. At this time, you need to remove it and clean it, and add a little watch oil.

2. The pointer rotating shaft is dirty and should be cleaned.

3. There is contact between the toothed rod pressing piece and the toothed rod, it should be loosened.

4. The oil return of the buffer is not good and should be adjusted or cleaned.

5. The belt on the force measuring piston is off or too loose (so that the piston cannot run at a constant speed).

6. The friction force of the force measuring piston in the cylinder increases or becomes stuck. Use chromium oxide abrasive paste to grind until it is normal.

7. The pendulum has obstructions during the raising process, or the pendulum shaft is too dirty or rusted, which makes the pointer return to zero change greatly.

(2) The passive needle cannot stop at any position well, and it does not overlap with the main needle.

The troubleshooting method is to remove the dial glass, adjust the passive needle pressure spring screw, and adjust the pointer so that it coincides with the main needle.

(3) When doing a tensile test, the sample fracture is always broken on both sides. The reason for this phenomenon should first be considered whether the main part of the testing machine is installed vertically. If this reason is eliminated, then the following three aspects should be eliminated.

1. The jaws are not placed correctly when clamping, and the sample should be clamped symmetrically with the jaws as required.

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

3. Improper adjustment of the lifting guide wheel makes the upper and lower jaws not concentric. A test rod should be processed, and after the upper and lower jaws are tightened, measure with a dial indicator based on the two force columns until the adjustment is qualified.

The return of the hammer is abnormal, fast and slow.

Normally, just rotate the buffer to the proper position. However, if the oil hole of the buffer is blocked, or there is dirt or the gap between the steel ball of the buffer valve and the inlet is too large, the buffer will fail. The solution is to clean the buffer valve and adjust the gap between the steel ball and the valve seat at about 0.5mm. Place the oil needle knob to reduce the gap between the oil needle and the valve body, and relist the A.B.C mound mark. Also, when the temperature influence is great, the oil can be changed appropriately.

(4) When loading, the oil system leaks severely or the oil pipe ruptures.

First of all, check whether the joints of the oil circuit system are tightened. If the gasket needs to be replaced, replace it in time. If the tubing is ruptured, you need to replace the tubing with a higher strength. In addition, you should also observe whether the fuel delivery valve and the relief valve piston are top dead or reversed.

(5) After the sample is broken, the pendulum quickly falls back, causing shock. The main cause is the failure of the buffer. In addition to regular adjustments, consideration should be given to whether the oil is too thin or too dirty.

In short, always pay attention to the problems found during the use of the testing machine and eliminate them in time to avoid errors in your test results. This is to check and calibrate the testing machine regularly to ensure the normal use of the testing machine. In addition, we should also pay attention to the daily maintenance and maintenance of the equipment to extend the service life of the universal testing machine. Hope it can help everyone!