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High-end bearing manufacturing key technology

High-end bearing manufacturing key technology


At present, there is no significant deficiency in the types, varieties, and specifications of bearing products, and it basically has a relatively complete product line. However, the product mix is not very balanced. The production capacity of middle and low-end ordinary products has produced a situation of surplus, while the market of high-end products is still mostly occupied by foreign famous brand products. So far, no very significant breakthroughs have been made.

For the current situation of the technical quality level of Chinese bearing products, we can use the situation that the quality is not as good as people and the technology of high-end bearings is not as good as people to summarize.

Plain bearing because of the relatively mature technology, and basically there are no barriers to entry, whether large or small enterprises are able to produce, so its main price competition, so the domestic bearing both in the domestic market or on the export of export constitutes the main body of market. However, even some technical content is not high plain bearing, compare domestic and foreign famous brand bearing products, its accuracy and consistency in their performance stability and reliability life quality level there is still a large gap, bearing industry in the current stage in our country in the transformation and upgrade of the task, The most urgent thing to do is to adjust the product mix. 

Among them, the focus is to complete the strategic layout in the field of high-end bearings, so that it can achieve an effective breakthrough in the short term and occupy the main position in the highest point of technology. This is not only the basic demand for the continuous development of the bearing industry since the present but also involves the objective requirements of the security of our national economy and national defense. Bearing is a kind of precision mechanical product, so the process is naturally the focus of the bearing manufacturing process.

1. The premise of the implementation of the process is equipment

For example, the most critical final machining step in the manufacture of bearing rings is grinding. The equipment used is mainly a special grinder and superfinishing machine tools. First of all, we must meet the basic requirements of high precision and high efficiency. In the past, the bearing grinder is mainly controlled by electromechanical hydraulic semi-automatic, and automatic machine tools. With the development trend of technological progress, CNC machine tools dominated bearing grinder and superfinishing machine tools. The CNC grinder composed of the automatic production line is not only especially suitable for mass continuous production of ordinary bearings, but also very flexible, and can cooperate with the production of a variety of special bearings. Therefore, numerical control has become the main choice for many bearing enterprises to upgrade the processing equipment technology. Some types of bearing ring geometrical structure is relatively simple, the accuracy is not high, the use of PLC economic numerical control system can; Certain types of bearing rings are more demanding, such as raceways that must be machined into a logarithmic shape of "crown".General-purpose or high-end CNC systems should be used to meet the requirements.

2. Bottlenecks restricting the processing quality of high-end bearings

For high-end bearings, in addition to the gap between raw materials and heat treatment, the accuracy, and related problems are mainly reflected in the parts grinding, especially the batch processing accuracy and accuracy consistency.

(1) A representative example of precision bearings is angular contact ball bearings used for machine tool spindles. For example, bearing rings of P4 or higher have a great difference in machining accuracy.A good company's one-time pass rate is usually about 80%. The matching rate was 60%. Certain types of bearings (such as tapered roller bearings for wind turbine shafts) also have difficulty maintaining mass above P4.

(2) high-precision class I and class 0 rollers for cylindrical roller bearings and tapered roller bearings with P4 accuracy above cannot be mass-produced, and the processing quality of class II or class III rollers will also fluctuate.

(3) the dimensional stability of the parts can not be well controlled and guaranteed. Lapping stresses and deformations are too high and machining defects such as lapping burns and cracks occur from time to time.

3. Key technologies and measures to be adopted to break the bottleneck

(1) the use of high precision and stability and high reliability of the machine tool. For some bearing rings with complex shapes, it is necessary to use the grinder of the full-function numerical control system to call the function directly so that it can be controlled and interpolated in time.A high-speed motorized spindle is used for grinding the inner surface, and high stiffness hydrostatic grinding wheel spindle is used for grinding the outer surface to complete high-speed grinding. The use of semi-closed loop and closed-loop servo system to control it, and can complete the precise micro feed and compensation, feed resolution can imagine 0.25μm or 0.1μm, repeated positioning its own accuracy can meet 1μm or as high as 0.5μm; The use of high precision and stiffness and wear resistance of ball screw and guide rail and other moving parts; Granite beds with strong vibration attenuation and relatively low coefficient of thermal expansion are required for more accurate grinders using beds that are fully aged and stable and have relatively good vibration absorption.

(2) Active measurement method for grinding size control, the control accuracy of 3μm or greater to 1μm.Servo motor is used to drive and control the grinding wheel dresser to reduce the grinding wheel dressing interval and improve the quality of grinding wheel dressing. Or use a diamond grinding wheel and CBN grinding wheel with good shape retention to ensure the consistency of shape precision in batch processing.

(3) Through forging, finishing, or precision cold rolling, reduce the grinding allowance, and fully carry out additional tempering and cold treatment between each procedure, in order to eliminate the grinding stress and avoid excessive feed to produce defects such as grinding burns and cracks to improve the machining accuracy and surface quality.

(4) Pay attention to improving the manufacturing level of key parts such as rolling elements and cages. Especially for high precision cylindrical rollers and tapered rollers, the use of automatic production lines. High precision rollers must be completely stable and aged.

(5) to achieve the control of precision ultra-precision machining environmental conditions, give up the long-term practice of the open workshop or general air conditioning factory for bearing production. According to the requirements of constant temperature and humidity, vibration isolation, and cleaning, the environmental facilities in the processing area shall be strictly constructed or transformed.

(6) give full play to the characteristics of "master and inherit" in the production of precision parts, strengthen the skill training and experience accumulation of operators, strict process flow and process discipline, strengthen the quality assurance system, so that "software" and "hardware" match, so that the excellent hardware performance better efficiency.

The gap in the field of high-end bearings in our country, in addition to the overall technical level, is relatively low, the most important two problems are raw materials and manufacturing technology. In the use of manufacturing technology, equipment and processes are required to have a breakthrough, and also need to use sophisticated equipment and advanced technology to give high-end bearing its high precision and stability, making its own performance and stability, and long service life and reliability characteristic quality can be guaranteed and implementation. 

The international well-known bearing companies regard equipment and process as one of their own "technology bibles", which also shows that manufacturing technology is the core competitiveness of the development of enterprises from another side. At present, the bearing industry in our country is undergoing active transformation and upgrading, so we must take manufacturing technology as the focus of the main direction, complete key breakthroughs in the field of high-end bearings, and hope to make our country develop from a big bearing country to a powerful bearing country as soon as possible.

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