Precision cold rolling technology is a cold processing and forming method to obtain finished parts by extrusion and plastic deformation of ring-shaped rotary parts at room temperature. Precision cold rolling can make the size and shape of the workpiece as close as possible to the theoretical value of the finished part. Its advantages are. 1. It can significantly improve material utilization and processing efficiency. Compared with the traditional way of turning processing, precision cold rolling processing can increase the material saving rate by 10% to 15% or more, so as to realize the cutting processing of bearing rings and reduce the processing cost. 2. It can improve the quality of finished products. Because of the rolling method, the metal flow inside the part is continuous and complete, the metal grain is more uniform and small, the organization is more dense, so the strength of the part can be improved. At the same time, due to the existence of residual surface stress in the finished part, the deformation of the part after heat treatment is also smaller. 3. Can save energy and improve working environment. Compared with forging die, precision rolling requires smaller tonnage of equipment, which can significantly reduce the noise during processing and save energy. Compared with turning billet, its noise and dust are smaller. When tumbling workpiece, the tumbling wheel drives the workpiece to rotate and the core roller squeezes the workpiece under the push of the support wheel which is fixed to the feeding device, so that the workpiece can be tumbled. In terms of the force condition of the workpiece, the following conditions are met: the horizontal force of the workpiece must be balanced with the force applied in the feeding direction, which is the necessary condition for stable deformation; the force in the vertical direction of the workpiece must be greater than or equal to the push-out force generated by the deformation of the workpiece, which is the condition for the continuation of rolling. The above two forces are the horizontal and vertical components of the normal force in the contact arc between the support wheel or core roller and the workpiece. The deformation is effective when the feed of the support wheel is sufficient to ensure the plastic deformation throughout the whole wall thickness of the workpiece. Moreover, the amount of feed depends on the driving power of the tumbler, the thrust of the support wheel, the radius of curvature of the tumbler and the core roller. The amount of feed determines the length of the contact arc between the support wheel or core roller and the workpiece, which corresponds to the normal deformation force generated by the workpiece deformation, the longer the contact arc, the higher the deformation force. Because the radius of curvature of the inner and outer circles of the rolling wheel, core roller and workpiece are different, the deformation generated inside and outside the workpiece by each feeding is not equal. The deformation in the outer circle of the workpiece is larger than the deformation in the inner circle, and the difference of the inner and outer circle deformation will decrease as the rolling process continues. Roundness stick is used to control the cylindricity of the workpiece. During the rolling process, the roundness stick is always close to the outer circle of the workpiece, backing off as the outer diameter of the workpiece increases and providing a constant rounding bending moment. The use of roundness stick can also ensure the smoothness of workpiece rolling process, effectively reduce the vibration in rolling and expanding, thus prolonging the life of die and machine spindle bearing. At present, foreign fine rolling equipment mainly includes URAW series of Germany BAD DUBEN and CRF and TCR series of Japan KYOEI company. They represent two technical lines respectively: BAD DUBEN adopts vertical arrangement and electro-hydraulic position servo control system to improve rolling accuracy, while KYOEI adopts horizontal arrangement and combination of rough rolling and workpiece diameter to improve the dimensional accuracy of workpiece.

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