Selection Standards for Spindle Bearings of Large Machine Tools
Bearing selection process The vertical turret lathe is classified as a cutting machine tool. In order to meet the relevant technical requirements, the bearing arrangement must have appropriate characteristics. The most important characteristics are: ■ Speed u200bu200bcapability ■ Running accuracy ■ Working life ■ Stiffness. According to the adjacent structure of the bearing, various bearing arrangements can be selected. The suggestions given below are the basic bearing selection process. In order to determine the final bearing type, setting values u200bu200band operating parameters, please contact the SchaefflerGroup Industrial application engineer. The calculation software BEARINX® can carry out bearing design and lubrication recommendations according to working conditions. You can use the template given in the appendix to collect working condition data, see page 157. The condition of the adjacent structure can determine the diameter of the faceplate (diameter of the turntable) through the size range of the workpiece to be clamped. The diameter of the main support bearing must reach 2/3 of the diameter of the turntable. If the diameter of the turntable is greater than 7 m, the bearing is allowed to use 50% of the diameter of the turntable. The speed is within the speed limit, continue to choose according to the speed that needs to be reached. Bearing speed capability is a prerequisite for perfect cutting, which mainly depends on the bearing type. In some cases, the heat generated by friction cannot be ignored, and lubrication must be used to dissipate heat. This demand reflects what kind of lubrication is needed. Workpiece accuracy The accuracy of the work piece depends on the running accuracy of the bearing, and the surrounding structure of the bearing also needs to have corresponding accuracy. Schaeffler Group Industrial TPI 205 11 rating life In order to achieve a sufficient fatigue life Lh, DAIDO bearings need to have a suitable load-bearing capacity. The term basic load rating used represents the load-bearing capacity of the bearing. The basic rating life of the bearing is affected by the load. On the other hand, it is affected by bearing size and type. In order to ensure the smooth running of the bearing, the safety factor is fS 4. The additional safety factor is usually not used in calculations. In special applications, such as permit instructions, internal instructions, requirements for maintenance, etc., appropriate safety factors should be used. Bearing dynamic load bearing capacity The bearing that bears the dynamic load is the bearing that mainly rotates. The bearing size is determined by the dynamic load bearing capacity. The size of the bearing under dynamic load can be approximated by using the basic dynamic load rating C and the basic rating life L or Lh. Generally, under different loads, one machine tool can process different workpieces. This means that the bearings may be subjected to different loads. In order to ensure that the performance of the bearing is acceptable, various load conditions must be considered during the bearing design process. If the bearing system adopts preload, it can ensure that the bearing has a necessary minimum load under various load conditions. The minimum load is required to ensure that the bearing does not slip and reduce friction and wear. The preload in turn can ensure the rigidity of the bearing system. The performance of more detailed guidance bearing arrangement is also affected by cleanliness and assembly accuracy. Therefore, this requires extra attention.