Due to long-term operation, the main shaft of the centerless grinder grinding wheel wears down the five tiles and the main shaft, resulting in a decrease in surface roughness and geometric accuracy, as well as a decrease in oil film rigidity. This causes the main shaft to experience radial runout under stress, resulting in the formation of vibration patterns on the workpiece. Due to the decrease in lubricating oil viscosity, the bearing is in a boundary lubrication state, and the larger bearing load causes abrasive particles to scratch the lubricating oil film on the working surface of the friction pair, resulting in high stress solid-phase contact,

1、 Scraping and adjustment of bearing shell (using centering process kit)

After even spots appear on the bearing shell, it needs to be finely scraped again. It can play a role in centering and aligning in each matching research, thereby shortening the adjustment time and overcoming the problem of side deviation caused by scraping the bearing shell.

When scraping, install the pre scraped pads and conical support screws into the box hole according to the design requirements, pay attention to the mutual position and rotation direction, then adjust the gap to make it tight and loose, and rotate the spindle according to the rotation direction of the grinding wheel. After lapping, remove all pads for fine scraping, and grind repeatedly until the requirements are met.

When fine scraping, it is necessary to scrape shallowly rather than deeply, and the points should not be too thin. The bearing shell should be scraped lower on the large end of the oil wedge to form an oil wedge. Although deep scraping can store oil, it can cause unloading and prevent the formation of the maximum dynamic pressure lubricating oil film

2、 Repair of spindle

For the worn spindle, when the wear amount is small and does not exceed the thickness of the hydrogenation layer, the working surface can be directly ground to restore the spindle accuracy and surface roughness; In addition, when there is significant wear, the chrome plating process can be used to restore the original size. After precision grinding and calendering treatment, the dimensional accuracy and surface roughness can be ensured. The trimming of the shaft end center is often overlooked, and the grinding of the center holes at both ends of the spindle is an important process related to repairing the spindle accuracy. When grinding the spindle center hole on a grinder, one hand should pinch the spindle, and the other hand should gently adjust the tailstock handwheel. The pinching of the spindle should be loose and tight to achieve the requirement of uniformly grinding the center hole. After the grinding of one end of the center hole is completed, the other end is ground again. After multiple repeated corrections such as grinding, measurement, and re grinding, the spindle's working surfaces meet the required technical standards.

3、 Repair of bearing shells

During the scraping and grinding process of the rough scraping bearing, a shallow scraping technique is used with a light blade. Firstly, rough scraping is carried out based on the main shaft, and the contact points are scraped out first. The points should be uniform, ranging from 14 to 16 points/25mm2, and the scraping marks should be repeated to ensure even distribution of the points.