Failure analysis of the hottest M1083A centerless

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Failure analysis and repair of M1083A centerless cylindrical grinder

M1083A centerless cylindrical grinder is a kind of metal cutting equipment. The equipment is characterized by good rigidity, high production efficiency and good equipment performance, which can meet the needs of mass production. The front and rear bearings of the grinding wheel and guide wheel main shaft adopt membrane feedback hydrostatic bearings, and the bearings have a symmetrical structure with four oil chambers. In the application of the equipment, the grinding wheel frame spindle hydrostatic bearing pair died, and the technicians successfully repaired it. The following summarizes the causes of equipment failure and the repair process of hydrostatic bearing pair in combination with the repair process

1. Failure cause analysis

the main reasons for the grinding wheel frame spindle (grinding wheel spindle) bearing grinding death are mainly in two aspects: the first is the blockage of the lubricating oil pump oil supply circuit; the second is the blockage of the main oil circuit entering the bearing oil chamber to remove the test piece. These two reasons will directly lead to insufficient lubricating oil entering the bearing oil cavity or insufficient oil pressure, which will lead to the grinding failure of the bearing pair when the spindle of the grinding wheel frame is started

the blockage of the oil delivery circuit is mainly at the oil filter. There are triple oil filters on the M1083A oil supply circuit, especially the fine filter is easy to be blocked or the paper of the filter element melts, causing the oil supply pressure to drop, the oil volume is insufficient, and the oil pressure is too low. At the same time, the interlock system of the main shaft starting appliance fails, resulting in the grinding death of the hydrostatic bearing pair

the oil passage into the bearing oil cavity is blocked mainly at the clearance of the film feedback throttle valve. When the clearance is seriously blocked, the amount of oil entering the oil chamber is very small, the oil pressure is very low, and the main shaft cannot float well in the bearing. If you pull the grinding wheel, it will not rotate or be very heavy. At this time, once the grinding main shaft is started, it will also cause the hydrostatic bearing pair to grind to death

1.2-? The fit clearance between 105mm and bearing is 0.055 ~ 0.060mm

2.2-? 105mm ovality, taper tolerance 0.002mm

m1083a grinding wheel frame spindle diagram

2 Repair process

after the spindle of the grinding wheel was removed, it was found that the fault was mainly in the front bearing of the spindle, while the rear bearing had no obvious signs of grinding death. First, we use a micrometer to accurately measure the front Journal of the main shaft. The actual size is 007mm, the diameter of bearing inner hole measured by inner diameter dial indicator is? 105+0.048+0.051mm, it can be seen that the fitting clearance is between 0.055 ~ 0.059mm, while the fitting clearance of hydrostatic bearing pair is required to be 0.006d (D is the nominal size of main shaft journal), M1083A main shaft journal d=105mm, and its fitting clearance technical requirements should be 0.063mm. The fit clearance required by the design is 0.055 ~ 0.060mm. The actual measurement shows that it can basically meet the fit clearance requirements between the main shaft and the bearing. The roundness error of the main shaft journal is 0.001mm, which meets the 0.002mm roundness tolerance required by the drawing, thus ensuring the rotation accuracy and stiffness of the main shaft components of the equipment

it can be seen from the removed main shaft that there is no obvious scar on the surface of the main shaft journal. Polish the surface of the main shaft on the C lathe to make the surface reach Ra0.8 μ M requirements: re measure the main shaft journal after polishing, and its size is 008mm。 In addition, if there are obvious scars on the surface of the main shaft journal, the main shaft journal must be finely ground to ensure the surface roughness: if the journal becomes smaller after grinding and cannot meet the requirements of the fit clearance between the main shaft and the bearing, the main shaft journal must be reliably rinsed and repaired to ensure that the fit clearance between the main shaft and the bearing pair meets the technical requirements, otherwise the rigidity and normal operation of the equipment will be seriously affected

check the inner hole of the bearing and find that there are obvious friction marks on the front bearing hole, while the accuracy of the main shaft journal is basically within the allowable range by checking, and the main shaft out of tolerance factor is eliminated. At the same time, check the lubricating oil circuit and find that the oil circuit is seriously blocked. After the polishing of the main shaft journal reaches the required surface roughness, the repair of the bearing inner hole is more complex, difficult to operate, and the accuracy is not guaranteed. First, according to the main shaft journal 008mm size and the required fit clearance between the main shaft and the bearing is 0.063mm. It is designed and manufactured with a diameter of? 105+0.038+0.040mm inspection mandrel, its taper and roundness tolerance is 0.002mm, as the final inspection tool, and at the same time, the grinding machine is designed and manufactured? When the 105+0.038+0.040mm mandrel can be smoothly inserted into the bearing bore and the mandrel is checked with Dan powder to ensure that the contact between the mandrel and the bearing bore is uniform, the repair of the bearing bore is basically completed. 4. Start the machine and pre add the lower limit test load. Finally, use the inner dial indicator to accurately verify the size of the bearing inner hole

the advantage of using a mandrel to inspect the inner hole is that the mandrel is small and can be measured at any time when grinding the inner hole, while the spindle is relatively large and heavy, which is not easy to move. In addition, the heart rod detection avoids unnecessary bumping of the spindle

when grinding the inner bore of the bearing, pay attention to frequent measurement, repeated grinding and repeated measurement until all requirements are met. It should be noted that when repairing the dead bearing hole, never scrape the bearing inner hole with a scraper, so it is very easy to make the coaxiality of the front and rear bearing holes and the roughness of the repaired bearing hole out of tolerance. At the same time, the pits caused by scraping are left on the inner surface of the repaired bearing hole, which will destroy the establishment of the main shaft bearing pair pressure zone during the repair and operation of the equipment

after repairing the main shaft journal and bearing hole, it is necessary to thoroughly clean all hydraulic components and oil pools of the lubricating oil circuit. In particular, the membrane feedback throttle valve should be repeatedly disassembled and cleaned with clean kerosene. On the premise of ensuring its original clearance g0=0.07mm and the oil supply pressure of the lubrication system p=1mpa, the four oil outlet pressures are equal. When there is no blockage, the spindle of the grinding wheel can be started only when it is easy to rotate the spindle by hand. Otherwise, the membrane feedback system must be disassembled and cleaned again. After the spindle of the grinding wheel is started, it is not allowed to apply load to the materials that are not convenient for hardness test. It can be put into production only after continuous idling for at least 4H and no abnormal conditions occur. So far, the dead grinding fault of the hydrostatic bearing pair has been completely eliminated

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