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Discussion on troubleshooting methods for hardness tester faults
2024-05-23
There are many types of hardness testers, and the commonly used ones in industrial and mining enterprises and research institutions are mainly metal Rockwell, Brinell, Vickers, and microhardness testers. Among them, metal Rockwell and Brinell hardness testers have a simpler structure compared to metal Vickers hardness testers. The repair of common faults is not very difficult. Below is an introduction to common troubleshooting of metal Vickers hardness testers.
Based on years of work practice, before starting calibration and repair work, it is necessary to start by adjusting the level of the workbench, and then observe whether the spindle, lever, lifting screw, buffer mechanism, and measuring device are normal and flexible. Ensure a basic understanding of device performance. Then, address each situation one by one.
(1) Load indicator light and measuring microscope light do not light up
First, check if the power supply is connected properly, then check the switch, light bulb, etc. If the light still does not turn on after excluding these factors, it is necessary to check whether all the loads are added or whether the reed switch is normal. If it is still abnormal after elimination, it is necessary to start from the circuit and gradually investigate.
(2) Measure the turbidity inside the microscope, and the indentation cannot be seen or clearly seen
This should start with adjusting the focus and lighting of the microscope. If it is still unclear after adjustment, the objective lens and eyepiece should be rotated separately, and the three flat mirrors with dotted, solid, and engraved lines inside the mirror should be moved separately. Carefully observe which mirror surface the problem lies on, then remove it, clean it with a long fiber degreasing cotton dipped in anhydrous alcohol, and install it in the opposite order before observation. If it is still not resolved, send it for repair or replace the micrometer microscope.
(3) The indentation is not within the field of view or slightly rotates the workbench, resulting in significant changes in the position of the indentation
The reason for this situation is due to the different axes of the indenter, measuring microscope, and workbench. As the pressure head is fixed at the bottom of the working shaft, adjust it in the following order. ① Adjust the clearance at the lower end of the spindle to ensure that the lower end of the guide seat does not directly contact the spindle cone; ② Adjust the screws on the side of the shaft so that the working shaft and spindle are at the same (axis) center. After adjustment, make an indentation on the test block, observe its position in the microscope, and record it; ③ Gently rotate the workbench (ensuring that the test block does not move on the workbench) and find a point on the test block that does not rotate under the microscope, which is the axis of the workbench; ④ Slightly loosen the screws and bottom screws on the pressure plate of the lifting screw rod, gently move the entire lifting screw rod to align the axis of the workbench with the position of the indentation recorded in the measuring microscope, then tighten the pressure plate screws and adjustment screws, and press an indentation to compare with each other. Repeat the above steps until they overlap. (Microhardness tester)
(4) Reasons and solutions for exceeding the tolerance of indication during calibration
① The measuring microscope scale is inaccurate. Use a standard micrometer for inspection. If not allowed, it can be sent for repair or replacement.
② Diamond indenter defect. Observe with an 80x stereo microscope to see if it complies with the diamond indenter calibration regulations. If there is any defect, replace the pressure head.
③ If the negative (load) exceeds the requirements of the regulations or the load is unstable, check with a small load third class standard dynamometer. If the load exceeds the requirement (± 1.0%) but the direction is consistent, this situation is a change in the lever ratio. You can loosen the spindle protection cap, turn the power point contact, adjust the load (lever ratio), and tighten it after adjustment. If the load is unstable, it may be caused by factors such as the force point blade becoming blunt, the fulcrum steel ball being worn, or the working shaft not being concentric with the main shaft, or significant friction inside the working shaft. At this time, check the blade and steel ball. If they become dull or worn, they should be repaired or replaced. Check the working shaft and clean it. Be sure to match the steel balls around the shaft. Refer to step 3 for the adjustment of the (shaft) center.
(5) Impact phenomenon during loading
This situation is related to insufficient or dirty buffer oil. After filling up the oil or cleaning the buffer, it can generally be solved.
