Rescue method for inner and outer diameter of bearing ring

First, the center offset method

1. Rescue the inner and outer diameter of the bearing ring

Firstly, the size of each defect (asymmetric type) existing in the part is accurately measured, and the minimum amount of grinding (the amount of grinding to the deviation of the finished product size) M is calculated, and then the center is offset at the time of grinding ( To offset the direction in which the amount of wear is increased at the defect, the maximum offset is M/2, that is, the relative amount of wear at the defect is increased, and the focus is sharpened.

2. Rescue of the inner and outer raceways of the ferrule

The design standard of the grinding ring of the bearing ring is the inner diameter or the outer diameter, that is, grinding the inner (outer) diameter and grinding the raceway first. Taking the inner ring as an example, if there is an asymmetrical defect in the inner raceway, it is necessary to accurately measure the The inner diameter of the part is calculated, and the maximum grinding amount M and the maximum grinding amount M1 at the inner raceway defect are calculated. When M1<M, the inner ring center offset is required when grinding the inner diameter, and the maximum offset is M1/2, that is, when the inner diameter is processed, the inner raceway defect is firstly increased in advance, and then the grinding is performed. When the raceway is rolled, the defects will be sharply ground and the waste will be saved. When M1 ≥ M, normal grinding can not be ground, according to the situation can be saved by the method described in section 1.1.

Grinding by center offset method is carried out under the premise of ensuring the hardness of the part and the depth of the carburized layer. The total offset cannot be completed in one offset grinding. Generally, it is divided into several grindings, that is, the offset test. Grinding - Measuring - Adjusting the offset - Repeat the process of re-grinding. After the defect has been worn away, re-align it and normal grinding to correct the ellipticity. This method is less efficient, and requires the operator to have a higher level of technology, but in this single-machine, single-piece production, this method has a higher success rate and does not delay the production schedule. After several years of practice, the effect is good.

Second, heat treatment upsizing method

The quenched structure of the bearing steel consists of quenched martensite, a small amount of undissolved secondary carbide, and approximately 12% to 14% of retained austenite. The quenched martensite and retained austenite are unstable structures. During the tempering process, the decomposition of martensite shrinks the volume of the steel, and the decomposition of the retained austenite causes the volume of the steel to expand.

With the increase of tempering temperature, the amount of residual austenite transformation and decomposition increases. Under the condition of ensuring the hardness of the process, the tempering temperature is appropriately increased to decompose the retained austenite and transform into martensite with larger specific volume. The structure can increase the volume of the workpiece correspondingly, that is, increase the grinding capacity of the outer diameter. With this method, the parts of the bearing ring which are defective under normal grinding conditions can be saved.

This method is more effective for thick and heavy workpieces with a large residual austenite content (especially for spherical roller bearings). In the actual production, different tempering processes are formulated for parts of different specifications, different sizes and different thicknesses. Under the premise of ensuring hardness and deformation, the organization is fully transformed, resulting in a large increase, correspondingly increasing the amount of grinding and saving waste. .

Third, chemical deposition

For bearing parts with dimensional tolerances exceeding the design criteria, chemical deposition can be used for salvage. The principle of chemical deposition is to uniformly produce a certain thickness of metal plating on the surface of the part through chemical reaction between various chemical materials, and to ensure the same hardness and mechanical properties of the metal layer and the part by additional tempering. Chemical deposition only increases the size of the part and does not change the shape tolerance of the part. Therefore, chemical deposition is an effective salvage method for parts with poor dimensional tolerance. At present, the maximum unilateral deposition thickness can reach about 0.1 mm.

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How to design adjustable clearance rolling ball bearings?

Design method of adjustable clearance rolling ball bearing:

Rolling ball bearings are widely used in production and life due to their many advantages such as low frictional resistance, sensitive start, high efficiency, high rotation precision, simple lubrication and easy replacement. However, due to its high manufacturing precision requirements and complicated process, the current standard rolling bearings are produced by special machines and manufactured by professional factories. Since the original design rarely considers the adjustable link between the rigid parts of the inner ring, the outer ring and the rolling element of the bearing, the important precision index of the bearing, the radial clearance, is mainly guaranteed by the machining tolerance. Thus, even if a higher precision machine tool is used to machine the bearing parts, it is difficult to achieve the required accuracy by direct assembly due to the inevitable accumulation error. Generally, it is necessary to assemble by means of measurement and assembly by group assembly method, but the accuracy is limited, so that the price of high-precision bearings is high. At the same time, the clearance of the bearing caused by wear and tear during use can not be compensated, which reduces the actual service life and causes waste. With the development of production, there is an urgent need to solve this technical problem. To this end, after analysis and research, the author has found the main factors that restrict the accuracy of radial clearance of bearings. Then, from the reasonable design of the bearing structure, a novel structural form is designed to make the radial clearance of the bearing can be easily adjusted, and the above technical problems are solved. After trial use, the effect is better, and it is now briefly introduced.

1. Design ideas, working principles and specific structure

It is well known that to adjust the radial clearance of the bearing, the relative positional relationship of the outer ring, the inner ring and the rolling element must be changed. It is intuitive to change the outer diameter of the inner ring or the inner diameter of the outer ring as needed. For ball bearings, there is a method of machining the inner bore of the inner ring of the bearing into a certain taper, and the corresponding journal is also processed to have a corresponding taper. After assembly, the position of the inner ring on the shaft is changed by an additional device on the shaft, and the inner ring is deformed to cause a change in the outer diameter to adjust the clearance of the bearing. In all fairness, this is a better method, which can solve the problem to a certain extent, so it has been inherited so far. However, there are also several obvious shortcomings. First, the amount of adjustment is limited (even very small), and when the play is large, it is not enough. Second, it is necessary to process a high precision taper at the journal, and additional adjustment devices are required to make the manufacturing process of the shaft complicated. Third, the inner ring is subjected to a large prestress, and is a circumferential tensile stress, which is extremely unfavorable to the bearing strength. Sometimes the inner ring may even “break without breaking” when adjusting. It can be seen that this traditional method is not reasonable and needs to be improved.

Analysis of the bearing structure shows that the article has been done on the inner ring, and there seems to be no potential to dig. The rolling element is also a "iron plate", which is obviously "unprofitable." Naturally, we turn our attention to the outer circle. However, this part is really simple and simple, and it is impossible to start with a conventional idea. It is necessary to find another way. After meditation, many parties to ask for advice, repeated scrutiny, and finally opened. It is realized that changing the radial clearance of the bearing is like snoring. It is not only forced to attack from the front (radial), but also from the side (axial). The premise is that we must break through the shackles of traditional thinking and the restraint of customary forces, and must dare to innovate. Therefore, it is bold to imagine that the outer ring of the bearing is cut along the cross section and is divided into two (reverse thinking, simplified to complex). The left and right halves are relatively axially movable, and then the relative axial displacement of the outer ring is converted into the radial displacement of the rolling elements by means of the interaction of the special curved surface on the inner raceway with the rolling elements, thereby receiving an indirect change. The effect of the radial position between the ring, the outer ring and the rolling element achieves the purpose of adjusting the play. Based on this, we can have the following technical solutions: the outer ring of the rolling bearing is changed from integral to axial split combination, with double row rolling elements, and auxiliary adjusting pad set. The radial clearance of the bearing is conveniently adjusted to the required value by increasing or decreasing the thickness of the adjustment pad during assembly, and finally the outer casing is integrally assembled by threaded coupling. In the same way, when the bearing is worn for a period of time, it is only necessary to appropriately reduce the thickness of the adjusting gasket, and it is easy to eliminate the bad play and restore the original precision. Reach the purpose of repair.

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