**Application and Function of Hydraulic Universal Material Testing Machine**
For many years, we have been deeply involved in the testing machine industry, gaining comprehensive insights into common issues that users often face. Below are some of the most frequently encountered problems and their solutions:
**1. Poor sensitivity of the dial pointer, with the needle stopping or shifting after unloading**
This issue can be caused by several factors:
- Dust and rust on the rack and pulley system—clean them thoroughly and apply a small amount of watch oil.
- The pointer's rotating shaft is dirty—clean it carefully.
- The rack and pinion are not properly aligned—loosen the connection if necessary.
- The buffer return oil is not functioning well—adjust or clean the system.
- The belt on the force measuring piston is loose or broken—tighten or replace it.
- Increased friction or sticking of the piston in the cylinder—apply chrome oxide paste to the surface until smooth.
- Obstruction during pendulum movement or a dirty/oxidized pivot—clean the shaft and ensure smooth motion.
**2. Oil leakage or damaged tubing during loading**
First, check all oil system connections for tightness. Replace any worn gaskets promptly. If the tubing is cracked, replace it with stronger material. Also, inspect the oil delivery valve and relief valve piston for proper function.
**3. Pendulum position is unstable or not vertical**
This may be due to high viscosity or contaminated oil—replace with the correct grade of oil. If the force measuring piston has excessive friction or doesn’t rotate smoothly, check if the machine is level and address any mechanical issues. Unstable friction can also be resolved by cleaning the pendulum shaft, gear rod, pointer, and wire wheel, adjusting the machine’s level, and reducing friction.
**4. Hammer movement is uneven (too fast or too slow)**
The buffer should be adjusted to the correct position. If the damper’s oil hole is clogged or the ball and valve seat are improperly seated, clean the valve and adjust the gap between the ball and seat to about 0.5mm. Adjust the oil needle knob to reduce the gap between the needle and the valve body, and re-mark the ABC scale. In cases of temperature influence, consider replacing the oil with a more suitable type.
**5. After sample failure, the pendulum drops quickly, causing impact**
This is typically due to a faulty buffer. In addition to regular adjustments, check whether the oil is too thin or too dirty.
**6. The secondary needle does not align with the main needle at any position**
Remove the dial glass, adjust the compression spring screw of the secondary needle, and ensure it aligns with the main needle.
**7. Sample fractures occur at the edges during tensile tests**
First, verify that the test machine is installed vertically. If this is not the case, check the following:
- Ensure the jaws are properly clamped and symmetrically positioned.
- Check the alignment of the upper and lower jaws—use a test rod and measure with a dial gauge to ensure concentricity.
- Inferior jaw quality or damaged teeth can cause slippage during testing—replace the jaws if necessary.
By addressing these common issues, users can maintain the accuracy and efficiency of their hydraulic universal testing machines. Regular maintenance and proper calibration are essential for reliable performance.
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