Abstract: According to the properties of high plasticity material and the structural characteristics of bearing cage, the processing technology of high plasticity bearing cage is discussed.
Keywords: rolling bearing; Cage; plasticity; Processing technology
In order to meet the requirements of high speed and long life of bearings, the cage material is made of PTFE with WARON, which is newly developed in recent years. Compared with the traditional metal or bakelite cage, the new material cage has the characteristics of light weight and wear resistance; However, it has strong plasticity and large deformation due to temperature difference, so it is easy to deform during processing and difficult to process. According to the traditional processing technology, it is difficult to ensure the design requirements of the product. Therefore, the processing technology of the cage must be re studied.
1 Preparation of processing technology
The original technological process of this type of cage of our company is: forming → rough grinding of outer circle → turning two end faces → fine turning of inner circle → drilling and reaming → final grinding of outer circle → final turning of inner circle → deburring → final inspection → packaging. According to the characteristics of the new material cage that is easy to deform under the action of cutting force and cutting heat, a set of processing technology suitable for this type of cage has been developed through repeated tests. The technological process is: forming → rough grinding of outer circle → turning two end faces → final grinding of outer circle → fine and final turning of inner circle → drilling and reaming → deburring → final inspection → packaging.
1.1 Inner and outer circle machining of cage
The original process is to drill and ream the cage first, and then finish the inner and outer circles. When grinding the outer circle, due to the influence of the cage pocket, the resistance of the outer circle is uneven, that is, the resistance of the pocket and the beam between the two pockets is inconsistent, so the roundness of the cage outer circle after grinding is not good. When finishing the inner circle, the outer circle and the plane are positioned. At this time, the inner circle of the final car is cut discontinuously, and the cutting conditions become worse. With the influence of the outer circle roundness, the roundness of the inner circle after finishing cannot meet the design requirements.
The improved process is to finish the inner and outer circle of the cage, and then drill and ream the hole. When grinding the outer circle, the resistance of the outer circle of the cage is uniform, and the resistance to deformation is relatively strong. Because its thin wall is easy to produce plastic deformation, when the machining allowance is about 0.5 mm, the feed rate of the grinding wheel shall be reduced, and each feed rate of the grinding wheel shall not exceed 0.08 mm, so as to reduce its deformation and obtain a high-precision outer circle. When finishing the inner circle, the outer circle and the plane shall be positioned. When installing the outer circle, the clamping force shall be as small as possible, and the rake angle of the turning tool shall be larger to reduce the cutting force and the deformation of the cage during processing. Because the final turning of the inner circle is continuous, the cutting amount is very uniform, and the cutting conditions are relatively good, the ideal inner circle size, accuracy, and coaxiality with respect to the outer circle can be obtained.
1.2 Drilling and reaming
As the new material cage is made of soft material and thin wall, which is easy to deform and break, two points should be paid attention to when drilling and reaming: first, the drill and reamer should be sharp and the feed speed should be slow when drilling and reaming to reduce the cutting force and ensure the machining accuracy of the pocket. Second, the clamping force shall not be too large during clamping. The jig of the drilling machine is shown in Fig. 1. If the clamping force of the clamp is too large, the spacing between the inner and outer locating discs will be reduced, which will lead to the deformation of the machined cage as shown in Figure 2. The greater the clamping force, the greater the cage deformation; The more the radial pockets are, the smaller the axial clamping resistance of the cage is, and the greater the deformation is. The deformation directly affects the dimensional accuracy of the pocket, the form and position tolerance of the pocket to the base surface, and the geometric accuracy such as the equal difference of the pocket.
1 - Bushing; 2 - Dividing plate; 3 - Nut; 4 - Pull rod; 5, 11 - washer; 6, 10 - round nut; 7 - Handle; 8-pin; 9 - key; 12 - Lock nut; 13, 16 - felt ring; 14 - phantom; 15 - Bearing; 17 - shaft; 18 - Screw; 19 - External locating disc; 20 - Split washer; 21 - Internal locating plate
Figure 1 Radial Jig Assembly
Figure 2 Cage deformation
2. Improvement of drilling and reaming tooling
When drilling and reaming, to ensure the geometric accuracy of the radial pocket, the geometric deformation of the cage must be eliminated. Therefore, the internal locating plate of the radial drilling jig is designed more accurately and reasonably, as shown in Figure 3.
Fig. 3 Internal Positioning Disc of Radial Jig
The original design L value is 0.2~0.5 mm, but now the design L=Bmin - 0.05 mm, D=dm in - 0.05 mm (where Bm in is the minimum width of the finished cage and dmin is the minimum inner diameter of the finished cage). The inner and outer positioning discs can not only clamp the workpiece, but also control the clamping deformation of the workpiece within the tolerance range of the finished product. Its working principle is as follows: the spacing between the inner and outer locating discs is too small due to excessive clamping force in the axial direction of the locating disc; It also supports the workpiece wall in the radial direction, so that the clamping deformation does not exceed 0.1 mm, thus effectively ensuring the geometric accuracy of the radial pocket.
3 Conclusion
Through process improvement, we have mastered the processing technology of bearing cage with high plasticity material, such as PTFE added with WARON. The test shows that the performance indexes of the cage parts processed by this method can fully meet the design requirements, and the bearing products can fully meet the needs of the host after being installed and used. The successful application of high plasticity materials in bearing cages has created economic benefits for the company. At the same time, it can be used for reference and promoted in the same industry and similar products, with certain social benefits.
More about SUNSPEED Rolling Bearings:
Rolling bearings support and guide rotating or oscillating machine elements such as shafts, axles or wheels and transfer loads between machine components. They provide high precision and low friction and therefore enable high rotational speeds while reducing noise, heat, energy consumption and wear. Rolling bearings are cost-effective and exchangeable machine elements that typically follow national or international dimension standards.
Roller bearings also known as rolling-element bearings are similar to ball bearings in that they are designed to carry a load while minimizing friction. However, roller bearings transmit loads using cylinder rolling elements, rather than balls, to maintain the separation between moving parts of the bearing. These versatile bearings can contain single or multiple rows of rolling elements; multiple rows can significantly improve radial load capacity. Also, the use of different roller shapes can further reduce friction and support both radial and axial loads.
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