The hydraulic universal material testing machine is an instrument that is often encountered in the verification of mechanical metrology. The JJG139-1999 verification regulations require that the allowable error of its indication generally does not exceed ± 1%. It is reflected in the following ways:
1. The positive deviation of the indicated value is excessive.
Second, the negative deviation of the indicated value is excessive.
3. Indication error shows "front positive and negative" or "front negative and positive" on the dial and individual points are out of tolerance.
In view of the above, the author believes that the following adjustments should be made:
The first situation: After confirming that the installation level of the instrument meets the requirements of the regulations, first check whether the friction force of the working part is too large. If it is, adjust the gap between the guide wheels to eliminate the friction force and clean the working oil cylinder if necessary. After the force is affected, there is still a positive difference, then the fastening screw of the connecting rod of the swing rod and the push plate in the force measuring part (reading mechanism) should be loosened, and the push plate should be adjusted inward. The small dial is verified step by step and repeated several times until the verification is passed. If the small dial is qualified and the large and medium dials are still out of tolerance, the weights of B and C thallium should be increased appropriately until the verification is passed.
The second situation: first check whether the force measuring piston is installed correctly and whether the friction force is too large. After eliminating this reason, adjust the push plate to the outside and adjust the small dial to pass. If the large and medium dials are still out of tolerance, The weight of B thallium and C thallium should be properly reduced until the test is passed.
The third situation: At this time, the angle of the contact surface between the push plate and the rack head should be changed. The contact surface is usually fixed on the surface of the push plate by a flat steel plate through the upper and lower screws. The adjustment method is to loosen the two screws Open, use copper skin or other thin and light metal sheet to pad on the upper or lower side between the steel sheet and the push plate (only on one side), in order to change the angle, after repeated verification and adjustment until qualified.
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