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What restricts the quality of high-end bearing processing?
Dec 03, 2018

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 consistency of parts grinding, especially batch processing accuracy and precision.

(1) A representative example of precision bearing is an angular contact ball bearing for machine tool spindle. For example, bearing rings of P4 or higher have large differences in machining accuracy. Certain types of bearings, such as tapered roller bearings for wind turbine shafts, also have difficulty maintaining accuracy above P4.

(2) High-precision Class I and Class 0 rollers for cylindrical roller bearings and tapered roller bearings with P4 accuracy or higher cannot be mass-produced, and the processing quality of Class II or Class III rollers may fluctuate.

(3) The dimensional stability of the parts cannot be well controlled and guaranteed. Grinding stresses and deformations are too large, and processing defects such as abrasive burns and cracks occur from time to time.

Key technologies and measures to be taken to break the bottleneck:

(1) Use the machine tools with high precision, high stability as well as high reliability. For some complex bearing rings, it is necessary to use a full-function CNC system grinding machine to directly call the function to enable timely control and interpolation; the inner surface grinding uses a high-speed electric spindle, and the outer surface grinding mainly uses high-rigidity static grinding wheel spindle to complete high-speed grinding; use semi-closed loop and closed-loop servo system to control it, and can achieve the accuracy of 1μm or as high as 0.5μm; use high-precision and stiffness and wear-resistant ball screws and guide rails.

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

(3) Reduce the grinding allowance by forging, finishing or precision cold rolling, and perform additional tempering and cold treatment between the processes to eliminate the grinding stress and avoid grinding defects such as burns and cracks.

(4) Improve the manufacturing level of key components such as rolling elements and cages. Especially for high-precision cylindrical and tapered rollers, use the fully automatic production lines. High precision rollers must be completely stable.

(5) Control the environmental conditions. Improve the processing environment according to the requirements such as constant temperature and constant humidity, vibration isolation and cleaning.

(6) Strengthen the skill training and experience accumulation of operators.

Please send e-mial to zysrobert@163.com if you have any question in high end bearings.