Sliding bearings can be divided into hydrodynamic bearings and liquid (or gas) hydrostatic bearings according to the way their oil film is formed. According to their force, they can be divided into radial sliding bearings and thrust sliding bearings. This article only describes the repair of several of these bearings.
1. Repair of dynamic pressure bearings
Repair of spindle accuracy. Under normal circumstances, the spindle can be repaired to restore its accuracy, and only when the hardness of the journal portion is reduced and uneven or flaw detection is found to be cracked.
The repair process is as follows: 1 repair the center hole at both ends of the spindle. The cylindrical rubber grinding wheel is clamped on the lathe with a three-jaw chuck, and the grinding wheel is made into a 60° cone with diamond, one end of the main shaft is placed on the top of the 60° grinding wheel, and the Other end is placed on the movable top. The outer circumference of the left end of the main shaft is supported by a center frame, and the center holes at both ends are respectively ground out, and then measured. Check the radial runout of the 1.5 conical surface at the front of the spindle. The requirements are within 0.002mm. If the tolerance is well marked, the directional grinding is performed to rotate the rubber grinding wheel at high speed. The other end of the main shaft is supported by the tailstock tip. The marks with different axial directions are ground upwards, and then the main shaft is slowly rotated, but the top holes are prevented from being made into an elliptical shape. 2 Grinding shaft diameter on the outer cylindrical grinding, the surface roughness value is required to be Ra=0.32μm or less, and the end surface of the main shaft is in contact with the gasket, and the roughness is required to be within 0.002mm of Ra=1.25μm. 3 Grinding spindle diameter The spindle is placed on the top of the spindle. The cast iron plate is first ground on the grinding plate, coated with alumina powder abrasive to manually drill the spindle diameter, and then polished with Ra=0.042μm.
2. Repair of short three-watt structural bearings
Firstly, the repair of the spindle is carried out, and the repair process is the same as the repair of the spindle of the dynamic pressure bearing. Secondly, we need to pay attention to the following problems: the two main shaft diameters and one working surface of the shoulder before and after fine grinding on the outer grinding, the size of the front and rear main shafts should be the same, the radial circular runout is within 0.002mm, and the surface roughness value is required to be Ra= 0.042μm or more, the grinding degree can be achieved, the runout of the shoulder is required to be within 0.005mm, and the surface roughness value is Ra=0.25μm.
The repair of the bearing bush, the short three-watt structure of the bearing bush in addition to the serious pull-up heat to lead out the lead in the bearing bush, the general situation can be repaired.
The repair method is as follows: 1 When the bearing is disassembled, the ball screws of each bearing bush and its paired phase are tied together (the original number is better) to avoid error adjustment. 2 The ball screw is stuck on the lathe, and the contact rate of the spherical surface of the grinding bush is increased to 70% or more. 3 Use the already repaired main journal as the reference to rough the bearing bush to a uniform display contact point. 4 honing the bearing bush to rotate the honing shaft on the lathe, the bearing bush is placed on the grinding shaft, and the hand is pressed and reciprocated until the main bearing is fully developed. The honing is to continuously flush with kerosene, and the surface roughness value after smashing can be reached. Ra = 0.1018 μm or more, and the contact ratio with the spindle is 80% or more. 5 The diameter of the honing shaft should be 0.03~0.05mm larger than the spindle journal. The formula ratio of the abrasive is 100g for epoxy resin 6101, 200g for alumina with 320 grit, and 14-16g for ethylene. Butadiene 20g.
The method of making the honing stick: 1 firstly weigh the epoxy resin and the dibutyl ester and then add the alumina powder to stir it. After it is fully diluted, add more ethylene and press it. After fully stirring, pour it into the mold quickly. 2 ç© abrasive should be cleaned with acetone or gasoline before injection into the mold, then apply the release agent on the inner hole of the outer pad, then mold the abrasive after the mold is installed, and then remove the outer cylindrical grinding machine to grind the outer grinding after curing. The size of the cut is 0.03 to 0.05 mm larger than the actual size.
Pay special attention to the repair of short three watts. We have some misunderstandings about the repair of short three watts in the repair of the grinding machine. The reason may be that we do not understand the short three watt materials.
The following describes the repair steps of short three watts: firstly, the removed bearing bush should be carefully checked. Because the surface material of the bearing bush is cast copper alloy ZQPB30, sometimes the lead is melted and precipitated in the copper layer due to excessive temperature during use. At that time, the naked eye could look black and there were many micropores, which indicated that the lead in the bearing bush had been precipitated. This is that the bearing bush can no longer be used and must be replaced. If the surface is shiny, it can be repaired only by the thin line traces generated by friction with the main shaft. If the spindle is repaired, either the new or the old tile should be in good contact with the repaired spindle neck. Since the diameter of the outer diameter of the repaired spindle bearing neck is certainly smaller than the standard size, it is necessary to repair the bearing pad to make the contact greater than or equal to 80%. Since the material used for the bearing bush is cast copper alloy ZQPB30, the material is soft and should not be scraped with a scraper. Generally, there is no special mechanical equipment for machine scraping and machine planing, which should be repaired by honing or grinding. There are two ways to do this. The most formal one is the honing repair, and the other is the more convenient research and repair.
Honing and repairing, the honing shaft is clamped on the lathe, the bearing bush is placed on the outer circle of the running honing shaft, and the hand is pressed and axially moved to both ends, so that the traces of the surface are completely eliminated, and the kerosene is continuously cleaned when honing. The surface roughness value can reach Ra=0.02μm, and the contact surface can reach 80%. For example, a slightly small thin line phenomenon can be scraped off with a scraper and then honed. The biggest trouble with honing is to make a honing stick. The method of making the honing stick and the method of making it have been explained above.
Grinding and repairing, the shaft for grinding and polishing can use the outer circle of the babbitt alloy, and the outer circle should be larger than the actual size of 0.01~0.02mm. If there is no Babbitt alloy, it can be replaced by cast iron HT205. The amount of grinding in the external turning should be larger than the actual journal size by 0.01~0.02mm, and the surface roughness value is Ra=0.8μm. Running on a lathe, chrome oxide kerosene is used as a polishing agent and applied to the grinding shaft. The method of honing the bearing bush is used to grind the bearing bush. This method is simple and practical (note that the chrome oxide powder is not lower than 320#).
After the surface of the bearing pad is repaired, the surface and the spindle should be colored. Use Prussian oil as a coloring agent, apply thinly and evenly on the spindle neck, gently place the bearing bush on the spindle neck and press it with both hands. Sliding back and forth in the radial direction at a constant speed for 3 to 5 times to check if the contact surface reaches 80%, and whether it is concentrated in the center.
After the inner surface of the bearing shell is repaired, the contact between the back surface of the bearing bush and the spherical support screw is checked by coloring. At the time, it should be noted that the number of the spherical supporting screw and the bearing bush are consistent, and no mistake can be made. The contact area is required to be ≥70%. If the contact condition is found to be unsatisfactory, the abrasive mixture mixed with alumina powder and kerosene can be used to meet the requirements. The grinding method is to clamp the spherical screw on the lathe or the drilling machine, start the machine to make the ball screw run, and hold the bearing pad on the spherical surface of the supporting screw and the bearing bush by hand, and rotate the bearing bush from time to time so that the bearing bush can be supported on the supporting screw Have the ability to self-locate. After grinding, clean with clean kerosene. Generally, the qualified contact surface is required to grind the ball screw and the spherical surface of the bearing bush by hand, and immediately lift the screw, and the bearing bush should not fall. After the standard is reached, the spherical grinding is qualified. However, it must be noted that when grinding the spherical surface of the bearing bush screw, care should be taken not to damage the surface of the bearing pad, or to study the inner surface of the bearing pad after grinding the spherical surface.
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