Talking about the Fault Analysis and Maintenance of the Dynamic Pressure Bearing of Surface Grinder

MM7132 surface grinder, the outer circumference of the front and rear bearings of the grinding head is tapered, and there are only three equally spaced flanges in the bearing cone, and there are 12 axial grooves uniformly on the bearing. When the bearing moves axially, The radial clearance between the bearing and the shaft changes; when the bearing is tightened, only the internal clearance of the three flanges becomes smaller, and the remaining part is elastically deformed to form three oil wedges, which are integral three-oil wedge dynamic pressure sliding bearings. The bearing has a small clearance and good rigidity, and its lubrication method is self-priming lubrication. During the use, the grinding head has a shaft, vibration and heat.

First, analyze the cause of the fault

After analyzing the causes of the failure in the equipment, it was found that the surface of the journal part of the grinding wheel shaft in the surface grinder has longitudinal cracks, and the front and rear bearing appearances have no obvious defects, and the wear amount is not large. The grinding head is dismantled and tested. It was found that the grinding wheel shaft was curved, and only shallow longitudinal cracks were present in the journal portion. The outer cone flanges of the front and rear bearings are in good contact with the bearing housing bores, and there is no obvious damage to the inner bore of the bearing. Therefore, the main reason why the grinding head can not work is that the geometrical accuracy of the front and rear bearings changes, and the shape and size of the three oil wedges are inconsistent. Therefore, the plan to repair the repair is to repair the front and rear bearings and the hard chrome (0.02mm) repaired grinding wheel shaft.

Second, the combination of scraping and grinding to repair the bearing

The bearing is repaired by the combination of scraping and grinding. The front and rear bearings are first shaved, and the contact area is increased by grinding to reduce the surface roughness value. The scraping method is used for scraping and must not be scraped into fish scales.

1. Install the front and rear bearings to the working position, and grind a cylindrical mandrel with a length of 400mm (55mm in diameter) according to the bearing hole. The degree of grinding is subject to the rotation. Apply a thin layer of red dan oil on the mandrel, insert the mandrel into the bearing, adjust the tightness of the front and rear bearings, turn the mandrel, and pull out the mandrel to make a light scratch point. This work must be repeated to achieve uniform density in the three rectangular strip contacts on the front and rear bearing inner surfaces. Then grind a cast iron grinding rod with a diameter of 0.02mm and a length of 400mm which is smaller than the mandrel, and apply W5 chrome oxide paste to grind the front and rear bearings at the same time, tighten the front and rear bearings at any time and pay attention to remove the excess of the bearing end. Abrasives. After grinding, the contact surface of the bearing is a complete three rectangular contact strips, and finally the bearing housing is removed and carefully cleaned so that it does not have any impurities.

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Baosteel Group's new choice for bearing repair bearing supply

Baosteel Group has ensured normal production through bearing repairs, which has reduced production costs and contributed to environmental protection.

“Can the broken bearing be repaired?” Before 2006, it was something Wu Jianhua, the chief of the cold rolling mill workshop of Baosteel Branch, never thought about. However, in the exchanges between Baosteel and the world-renowned bearing supplier Timken, this “never” has begun to make new changes.

The cold rolling mill workshop of Baosteel Branch, where Wu Jianhua is located, provides the roll assembly for Baosteel's cold rolling production line. Now the roll assembly on the cold rolling mill of Baosteel Branch is provided here. This workshop is directly related to the normal production of each cold rolling line. Since the rotating rolls are to be matched with the bearings, the quality of the bearings directly determines the stability of the rolls and rolling, which determines the quality of the cold rolled steel products. Therefore, Baosteel never dared to be sloppy in the choice of bearings. Always use the most quality guaranteed bearings. However, the new problem is now in front of him, that is, "there is money and can not buy bearings."

Baosteel's roll bearings are made of four-row tapered roller bearings with a hole diameter of more than 350 mm, which belongs to the category of large-aperture bearings. Since the service life of the bearing is affected by the working conditions, the working condition of the rolling mill can be called “extremely bad” when rolling, so Baosteel's rolling bearing has a certain amount of replacement after inspection and maintenance every year. According to Wu Jianhua, “From the overall market in the world, there are so many new cold rolling projects, so the demand for bearings is growing exponentially. In addition, the prices of metal raw materials have risen in the past two years, and there is some disconnection in the bearing supply of the entire market. The actual situation is that you have money but can't buy bearings! Especially in 2006 and 2007, the large-aperture bearing supply and demand market has the biggest contrast, and it is out of stock. The company is quite nervous in purchasing large-aperture bearings. Timken started Baosteel in 2006. Providing bearing repair services is still very timely."

Indeed, if the equipment is not working properly due to the shortage of bearings, the cold rolling mill and the subsequent production line are likely to stop. This responsibility and difficulty will definitely put a lot of pressure on the production line. The problem can be solved smoothly, of course, it makes people feel a bit angry. However, the benefits of bearing repair services for Baosteel are by no means just a matter of urgency. Recently, steel companies have been increasingly affected by the rapid rise in the price of iron ore raw materials, and the cost pressure is high. Therefore, how to save costs has become an important issue that all steel companies must consider. Baosteel is no exception. “Baosteel has been vigorously promoting cost reduction, which is also in line with national resource conservation requirements.”

According to Wu Jianhua, the chief operating officer, “Baosting and Steel's means of reducing costs can be described as diverse, energy consumption is the key point, and equipment consumables can also be considered for cost control.” Bearing repair can indeed save Baosteel.

For the cold-rolling mill shop, the biggest cost item is the roll, and the other is the bearing. After the bearing that was found to be faulty, it will be disposed of as scrapped, and then replaced with a new one. "Our new bearing products are invested nearly ten million a year. Now we do find that technically, some bearings can be repaired after repair. After repairing, we can save at least half of the new product costs, and the repaired bearings can also be like The new one continues to be put into use, which is a big step in cost savings."

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