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Axial preloading method can be generally divided into positioning preloading and constant pressure preloading.
In the positioning pre tightening, the appropriate pre tightening amount can be obtained by adjusting the size of the bushing or gasket; The appropriate preload can also be adjusted by measuring or controlling the starting friction moment。
You can also directly use the paired double working in Timken bearings with pre adjusted preload to achieve the purpose of preloading. At this time, it generally does not need to be adjusted by the user. In short, the relative position of Timken bearings with axial preload will not change when used.
Constant pressure preloading is a method to preload Timken bearings with coil springs, Belleville springs, etc. The rigidity of the preload spring is generally much smaller than that of the Timken bearing, so the relative position of the Timken bearing with constant pressure preload will change in use, but the preload is roughly the same.
The feature of this Timken bearing grinding method is that all grinding allowance (0.20 ~ 0.60ram) is ground in a longitudinal cutter with a small longitudinal feed (f_; longitudinal = 0.08b ~ 0.15bmm / R). Using this grinding method, the grinding wheel needs to be trimmed to have a front cone (Fig. 7-5a) or a stepped shape (Fig. 7-5b)
In order to gradually cut the allowance, otherwise the cutting work is mainly concentrated on the outer corner of the grinding wheel, making the outer corner of the grinding wheel blunt rapidly, affecting the grinding efficiency and surface quality.
Attention should be paid to when trimming the stepped grinding wheel: the large cylindrical surface plays the role of fine grinding and polishing, so it should be trimmed more finely, and the rest of the stepped surface plays the role of rough grinding, and it should be trimmed more coarse.
In addition, the height of the step close to the outer layer of the workpiece should be larger, while the height of the step close to the finished surface should be smaller. In this way, we can obtain high productivity and ensure small surface roughness value at the same time.
However, dressing the grinding wheel is complex, and the structure of the workpiece must allow the grinding wheel to extend a large distance beyond both ends of the machined surface, so it is only applicable to some parts whose grinding structure meets the above requirements in mass production.
Tests in some factories have proved that the productivity of this grinding method is about twice that of the longitudinal grinding method, and sufficient accuracy and small surface roughness can be obtained at the same time.