Fault analysis of broken teeth of the hottest mqg3

2022-09-21
  • Detail

Failure analysis of broken teeth of mqg3660 ball mill

I. failure

mqg3660 ball mill, barrel size (diameter x length) is 3600mm 6000mm. After the installation of the ball mill, the sound is not normal during the no-load test run. After shutdown and inspection, cracks were found at the root of the small and medium-sized gears of the main drive gear. At that time, it was believed that the crack of pinion was caused by the gradual development of stress concentration caused by surface quality problems during its processing and manufacturing process. Replace a new pinion and put it into production trial operation after several days of no-load running in. After loading and running, abnormal meshing sound is generated immediately. After such intermittent operation for two months, the pinion gear teeth broke. Replace with a pinion again, the noise is still very high during operation, and it breaks again

according to the field analysis, the existing cause of meshing noise is that the meshing clearance is too large. Therefore, the meshing clearance of gear transmission is adjusted. After starting the operation again, the vibration and noise were reduced, but two months later, the pinion broke two teeth. Replace the fourth new pinion and adjust the meshing clearance as well. This time, after only 10 days of operation, the pinion teeth broke and the pinion seat was pushed outward by 3mm

II. Analysis of fault causes

there are two kinds of gear tooth fracture, one is bending fatigue fracture; The other is overload breaking. The main causes of fatigue fracture are: the dynamic load of the transmission system is too large; The fillet radius of the tooth root is too small; The tooth root surface roughness value is too large; The tooth root is strained during hobbing; There are defects in the material, small cracks and other harmful residual stresses caused by heat treatment

when the alternating stress at the tooth root exceeds the fatigue limit of the material, fatigue cracks occur at the fillet of the tooth root, and the cracks continue to expand, eventually leading to the bending fatigue fracture of the gear teeth. Overload fracture is usually caused by the impact load of short-term severe overload, which makes the stress on the gear teeth exceed its limit stress. Serious load concentration, excessive dynamic load and large hard foreign matters entering the meshing place of gear teeth can cause overload and fracture

the fatigue fracture of gear teeth is gradually produced under the long-term effect of alternating stress accelerating the development of aluminum based new material industry. Because the number of pinion teeth is small and the number of stress cycles is relatively large, fatigue fracture is also possible. However, the dynamic load of the transmission system of the ball mill is generally not very large. Moreover, before each replacement, the involute parameters, gear accuracy and surface quality of the new gear are measured and tested, and the test results meet the technical requirements of the drawing. Only from the time that the commercial development of MQ vanadium flow energy storage battery is facing severe challenges, and the pinion of g3660 ball mill is broken after several replacement, It should be the joint action of fatigue and overload

however, when breaking several times, there is no unexpected serious overload, there is not too much impact load in the work of the ball mill, and the transmission system will not produce too much dynamic load. In addition, each time the fault occurs, the meshing position of the two wheel teeth can reach 0.001 (1) 000mm/min, and the control and positioning is accurate, and there is no hard foreign matter in it. Obviously, the main cause of tooth fracture should be the serious concentration of load on the gear teeth. On this point, we can use w-b75 Vickers hardness tester, and the on-site personnel have verified it after coloring and checking the meshing of the two wheel teeth with red lead powder. The on-site inspection found that although the contact area of the tooth surface reached 90%, the coloring near the end of the cylinder was obviously heavier, while the coloring near the end of the coupling was obviously lighter, and the former accounted for only 50% of the tooth surface. Therefore, it is thought that several broken teeth are close to the end of the cylinder. It is precisely because of the concentrated working load that the pinion is broken many times

The main drive gear of mqg3660 ball mill is a pair of straight cylindrical gears. The main reasons for the uneven load distribution on the teeth of spur gears are: the tooth direction error produced in gear processing; Parallelism error between two gear shafts after installation. According to the on-site inspection results, the reason for the broken teeth of the machine is due to improper installation and adjustment

III. troubleshooting

make corresponding adjustments according to the technical requirements for the assembly of the main drive gear of mqg3660 ball mill: adjust the axial distance of the two gears according to the deviation range of the center distance of the gear pair, ensure the top clearance and side clearance between the two wheels, and measure the side clearance by pressing lead; Adjust the parallelism of the axes of the two gears so that the contact spot mark after coloring inspection in the direction of tooth width is centered; Grinding the tooth surface of the big gear damaged by broken teeth; Change splash lubrication to spray lubrication

after several repeated adjustments, the tooth surface contact spots reached 95%. There is almost no noise during the test run, and the vibration of the machine is very small. So far, it has been used for more than half a year, and the tooth has not broken again

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