Among the gold cutting equipment used by our factory, there is a M1083A centerless cylindrical grinder produced by Haining Machine Tool Plant. The equipment is characterized by good rigidity, high production efficiency, good equipment performance, and can meet the needs of mass production. The grinding wheel and the front and rear bearings of the guide wheel adopt the membrane feedback hydrostatic bearing and the bearing has a symmetrical structure with four oil chambers. The equipment has recently experienced failures in the grinding of the main shaft bearing of the grinding wheel spindle, and we successfully repaired it. The following is a summary of the reasons for the failure of the equipment during the repair process and the secondary repair process for hydrostatic bearings. 1 Analysis of Causes of Failure The main reason for the grinding of the grinding wheel spindle (grinding wheel spindle) is mainly in two aspects: The first is the blockage of the oil pumping circuit of the lubricant pump: the second is the blocking of the main oil circuit of the bearing oil chamber. These two reasons will directly lead to the insufficient amount of lubricant oil entering the bearing oil chamber or the insufficient oil pressure, which will lead to the failure of the bearing deceleration when the grinding wheel spindle starts. The blockage of the oil delivery circuit is mainly at the oil filter. There are three oil filters on the delivery line of M1083A, especially if the fine filter is easily blocked or the filter paper is melted so that the delivery pressure is reduced. The amount of oil is insufficient and the oil pressure is too low. At the same time, the spindle starter electrical interlock system fails, resulting in static Pressure bearing research died. The blockage of the oil path into the bearing oil chamber is mainly at the diaphragm feedback throttle gap. When the clearance is seriously blocked, the amount of oil entering the oil chamber is very low, the oil pressure is very low, the spindle cannot float well in the bearing, if the grinding wheel is toggled, it will not move or be very heavy. The main shaft also causes the hydrostatic bearing pair to die.
1.2-Ø105mm clearance with the bearing 0.055 ~ 0.060mm
2.2-Ø105mm ellipticity, taper tolerance 0.002mm
M1083A spindle frame spindle diagram
M1083A wheel frame spindle parts are shown on the right. 2 Repair process After we removed the grinding wheel spindle, we found that the fault was mainly in the front bearing of the main shaft, and there was no trace of death in the rear bearing. First, we use a micrometer to accurately measure the front spindle journal. The actual size is Ø105-0.008-0.007mm. The inner diameter of the bearing is measured with an inner diameter dial gauge to be Ø105+0.048+0.051mm. It can be seen that the fitting gap is 0.055. ~ 0.059mm, and the static clearance of the bearing pair requires 0.006D (D is the nominal size of the spindle journal), M1083A spindle journal D = 105mm, and the technical requirements of the fit clearance should be 0.063mm. The required clearance for design is 0.055-0.060mm. After actual measurement, it can basically meet the requirements of the clearance between spindle and bearing. The roundness error of the spindle journal is 0.001mm, which satisfies the 0.002mm roundness tolerance required by the drawings, thus ensuring the precision and rigidity of the spindle components of the equipment. From the removed spindle, it can be seen that there is no obvious scar on the surface of the spindle journal. We will surface polish the spindle journal on the C630-1 lathe so that the surface of the spindle will reach the Ra0.8μm requirement and the spindle will be polished after polishing. The journal was re-measured and its dimensions were Ø105-0.010-0.008mm. In addition, if there are obvious flaws on the surface of the spindle journal, the spindle journal must be ground to ensure the surface roughness: If after grinding, the journal becomes smaller and the matching gap between the spindle and the bearing cannot be met, it must be Spindle journals are reliably plated and repaired to ensure that the clearance between the spindle and the bearing pair meets the technical requirements, otherwise it will seriously affect the rigidity and normal operation of the equipment. Check the bearing bore, found that there are obvious signs of friction on the front bearing hole, and the spindle journal through the inspection of its accuracy is basically within the tolerance range, eliminating the spindle overshoot. At the same time check the lubricating oil road to find that the oil circuit is seriously blocked. After the spindle journal is polished to the required surface roughness, the repair of the bearing bore is more complicated, difficult to operate, and the accuracy is not guaranteed. We first design a test spindle with a diameter of Ø105+0.038+0.040mm according to the Ø105-0.010-0.008mm size of the spindle journal and the required clearance between the spindle and the bearing of 0.063mm. The tolerance of the taper and roundness is 0.002. Mm, as the final inspection tool, at the same time, the design and manufacture of the research Ø105+0.038+0.040mm mandrel can be inserted into the inner bore of the bearing relatively smoothly and the repair of the inner bore of the bearing when the mandrel is in uniform contact with the inner bore of the bearing is basically completed. Finally, the inner diameter of the bearing bore should be accurately verified with the inner diameter dial indicator. The advantage of using a mandrel to test the inner hole is that the mandrel is small. When the inner hole is ground, it can be measured at any time, and the spindle is relatively large and heavy and difficult to move. In addition, the spindle test is used to avoid unnecessary scratching of the spindle. When grinding the inner bore of the bearing, pay attention to ground measurement, repeatedly study, and measure repeatedly until it reaches all requirements. It should be noted that, when repairing the dead bearing holes, the inner hole of the bearing must not be scraped with a spatula, so that the coaxiality of the front and rear bearing holes and the roughness of the repaired bearing holes can be easily exceeded, and at the same time, the bearing is repaired. Holes on the inner surface of the hole are left as a result of scraping, and the spindle is destroyed when the equipment is repaired and the bearing is established. After the repair of the spindle journal and bearing holes is completed, all hydraulic components and oil pools of the lubricating oil road must be thoroughly cleaned. In particular, the membrane feedback throttle valve uses clean kerosene for repeated decomposition and cleaning. Under the premise of guaranteeing the original gap G0=0.07mm and the lubrication system supply pressure P=1MPa, the four outlet pressures are equal. In the absence of blockage, it is easier to gently turn the spindle wheel by hand to start the grinding wheel spindle. Otherwise, the film feedback system must be re-disassembled and cleaned. After the grinding wheel spindle is started, it cannot be rushed to apply load, and it must be put into production only after at least 4 hours of continuous idle operation without any abnormalities. At this point, the hydrostatic bearing vice research failure has been ruled out.
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