The main reason of shaft extension in the bending part of explosion-proof motor shaft

The bending position of Xi 'an explosion-proof motor shaft appears at the shaft extension, which is mainly caused by the sudden change of bending moment or torque added to the shaft extension by the pulley or gear coupled with the motor shaft extension. Secondly, the problem of the motor rotating shaft material, or the failure to carry out quenching and tempering treatment according to the regulations.

Therefore, to avoid shaft bending, firstly, the pulley tension and gear pressure should be adjusted to a proper state; The second is to verify the material of the shaft and carry out heat treatment according to the process requirements.

The causes of shaft breakage are mainly in design and manufacture; Secondly, it is related to excessive installation and correction errors or pulley tension and gear pressure, and the material of the rotating shaft does not meet the specified quality standards, or the rotating shaft is not quenched and tempered as required (preventive measures are the same as above). These secondary reasons are obvious and easy to find and deal with. However, the reasons for design and manufacture are hidden and should be listed as the main factors in the broken shaft. The countermeasures are as follows:

① When designing the rotating shaft, try not to have a concave groove, which is also the stress concentration point, and the fracture is easy to occur here. Be sure to add grooves, for example, when adding grooves for installing elastic retaining rings for shafts, the shaft at this position should be designed to be slightly thicker, or added to the external fan at the non-load end. Some manufacturers are worried that the grinding wheel can't grind the root shaft, and the root should not be grooved. Some manufacturers are worried that the grinding wheel can't grind the root, so it is unnecessary to add a hollow groove. Because there are chamfers or circles R in the inner holes of couplings, pulleys and gears. Changing the empty cutter groove into R1 and R3 will not affect the installation, but the shaft broken fault can be reduced. So should the bearing platform.

(2) when the diameter of the important official of the ribbed shaft is φ 200 ~ 350 mm, four 30~40mm thick ribs can be used. Because the metallographic structure of the weld will change, the physical properties of the shaft will decrease. If the number is increased to 6~8, the damaged areas may be connected into a circle, and the shaft may break here. The repaired explosion-proof motor once had an example that the rotating shaft did not break at the thinner shaft extension, but broke at the thicker welding rib.

In addition, it should be stipulated in the drawing that the rib and the shaft should be spot-welded together first, and then welded together while it is hot after being heated to 200~400℃. Because the weld here is relatively large, it should be welded in several times. Welding shall be carried out in hot state every time. Aging treatment after welding: heating to 600~700℃ for 1~2h, and then naturally cooling.