How to Improve the Qualification Rate of Short Cylindrical Roller Bearings

The short bearing.com/cylindrical-roller-bearings.html' target='_blank'>cylindrical roller bearing is a kind of bearing with high rotation precision, accurate fit and mainly bearing radial load. It is mainly used for the spindle of large precision machine tools and the roll support of finishing rolling equipment. Common models are fag nu211e.xl.tvp2, nsk nup313w*5, skf nnu4924bk/spw33, skf nu2230ecm/c3vl2071. In recent years, this type of bearing has become the leading product in the production and processing of the extra-large bearing division, and the output value accounts for about one-third of the division. However, due to following the old production process and processing method, the qualified rate of first-time matching of bearings is low (only 60%), resulting in a huge waste of materials and man-hours, thus affecting the further improvement of the economic benefits of the business unit. First, the selection of objects Short cylindrical roller bearings are divided into single row, double row, four rows and other categories, but carefully study their structural characteristics have many things in common: straight raceway, welding protector and so on. Therefore, the problems in the production and processing process are also very similar, so the content of the optimization process will be very similar, so the short cylindrical roller bearing with the largest annual output '32672' is selected as the representative to carry out the optimization process structure test, and the experience is extended to Other types of bearings are processed in order to obtain more considerable economic benefits. 2. Status of production and processing and existing problems 1. The inner and outer sleeves of the short cylindrical bearing are made of gcr15simn steel. The size series is large, and it is difficult to control the shrinkage and deformation during the heat treatment and quenching process. Grinding allowance, resulting in over-grinding of the inner and outer raceway dimensions. 2. Due to the quenching ellipse of the inner and outer raceways of the short cylindrical bearing, the allowance is not uniform, so that the residual stress of the processing is not uniform, which leads to the unstable size of the raceway after the final grinding of the ferrule, and it is difficult to control it within the specified range of the process. 3. During the initial grinding of the inner and outer raceways of the short cylindrical bearing, due to the aging of machine tools and other reasons, the rotation accuracy of the grinding head spindle is low, resulting in a large raceway facet after rough grinding, resulting in out of tolerance of the raceway size after final grinding. . 4. Technical coordination cannot keep up. Due to the above reasons, the bearing raceway is over-ground, which affects the assembly clearance of the entire set of bearings, resulting in unqualified clearance, resulting in the uncertainty of the bearing's center of rotation, resulting in too large or too small the center diameter of the cage (the center of the cage hole). The diameter of the bearing is processed according to the specified uniform size), which often causes the phenomenon of reduced bearing rotation flexibility and uneven clearance, which leads to the “32672” bearing. The qualified rate of one-time matching is only 60%. Unnecessary waste of retainer man-hours and materials. 3. Improvement plans and measures In view of the above problems, the original processing technology of the short cylindrical bearing has been optimized and improved, and the technical measures taken include: 1. In order to prevent heat treatment and quenching from leaving no allowance and large deformation, actively contact the heat treatment plant to cooperate with the control of deformation According to the heat treatment shrinkage data provided by the factory, properly adjust the raceway reserve. This ensures that after heat treatment and quenching, the grinding allowance meets the process requirements. 2. In order to prevent the dimensional instability after final grinding, an additional tempering process is added on the basis of the original processing technology, so as to eliminate the processing stress and ensure the stability of the raceway size. 3. Improve the surface finish of the initial grinding of the raceway by modifying and overhauling the machine tool equipment, improving the rotation accuracy of the spindle, and controlling the amount of feed to prevent the raceway from being over-ground. 4. By coordinating with the production scheduling department, on the premise of ensuring the production progress, the process structure is changed to first process the inner raceway which is greatly affected by the shrinkage, so that the technical personnel can analyze and calculate the inner raceway under the condition of over-grinding. , and formulate corresponding measures (the jacket can be properly under-ground and the center diameter of the retainer hole can be changed) to ensure the matching pass rate. 5. Compress the final grinding tolerance zone of the raceway, so that the size (one batch) is unified within a small range, and the difference between them is small. In this way, the qualified rate of first-time matching will be further improved, and a lot of matching clearance time will be saved. Since the optimized grinding process is used to guide production, the first-time matching pass rate of cylindrical roller bearings has increased from 60% to more than 96%, which greatly reduces the repair rate, saves man-hours and materials, and reduces production costs.

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