We introduced the craftsmanship of precision metal shafts to everyone, so today we will take everyone to know the installation knowledge of the precision shafts and explain them from the following three aspects.
1. Precise metal shaft requirements for matching parts
Since the precision of the precision metal shaft itself is within 1μm, it is required that the matching mechanical parts (shafts, bearing blocks, end covers, retainer rings, etc.) have high dimensional accuracy and shape accuracy. In particular, the precision of the mating surface must be controlled in the same direction as the bearing. Within the level, this is crucial, and it is also the most overlooked.
It must also pay attention to the matching mechanism of the precision metal shaft, if it does not meet the above requirements, it often causes the precision metal shaft to be several times larger than the original bearing error, or even more than 10 times the error, and it is totally not a precision metal shaft. The error of matching mechanism is often not simply superimposed on the error of the bearing, but is added after amplification with different multiples.
2. Precision metal shaft coordination
In order to ensure that the bearing does not produce excessive deformation after installation, it must:
(1) The roundness of the shaft and the seat hole and the perpendicularity of the shoulder should be required according to the corresponding accuracy of the bearing.
(2) It is necessary to accurately calculate the interference of the rotating ferrule, and also to accurately calculate the appropriate amount of the fixed ferrule.
It is also advisable to obtain a small amount of spinner ring interference in the possible range. As long as the effect of thermal expansion at the working temperature and the influence of the centrifugal force at the highest rotational speed are reliably ensured, the creeping or sliding of the close-fitting surface will not be caused. According to the size of the working load and the size of the bearing, the fixed ferrule selects a slight clearance fit or an interference fit. Too loose or too tight is not conducive to maintaining the original precise shape.
(3) If the bearing operates at high speeds and the working temperature is high, special attention should be paid to the fact that the fit of the rotating ferrule should not be too loose to prevent eccentric vibration, and the clearance of the fixed ferrule cannot occur to prevent the ferrule from becoming Deformation under load and excitation vibration.
(4) The condition of adopting a small interference fit for the fixed ring is that both mating surfaces have a very high shape accuracy and a small roughness, otherwise it is difficult to install and difficult to disassemble. In addition, the influence of the thermal elongation of the main shaft needs to be considered. .
(5) The main shaft of a paired double-angled angular contact ball bearing is used. Most of the load is lighter. If the fitting interference is large, the internal axial preload will be significantly larger, resulting in adverse effects. The use of the double-row short cylindrical roller bearing spindle and the tapered roller bearing spindle, the load is relatively large, so the fit interference is relatively large.
3. Improve the actual matching accuracy
In order to improve the actual fitting accuracy during bearing installation, it is necessary to use a measurement method and a measurement tool that do not deform the bearing to perform actual and precise measurement of the fitting surface dimensions of the inner hole and the outer circle of the bearing, and the measurement of the inner diameter and the outer diameter can be performed. All items were measured, and a comprehensive analysis was performed on the measured data. Based on this, the dimensions of the bearing mounting position of the shaft and the housing hole were precisely matched. When actually measuring the corresponding size and geometry of the shaft and the seat hole to be fitted, it should be performed at the same temperature as when measuring the bearing. In order to ensure a high degree of actual fitting effect, the surface of the shaft and the hole matching the bearing should be as small as possible.
In making the above measurements, two sets of marks showing the direction of the maximum deviation should be made on the outer circle and the inner hole of the bearing, and on the corresponding surfaces of the shaft and the seat hole, respectively, on both sides close to the assembly chamfer. In the actual assembly, the maximum deviations of the matched two parties are aligned in the same orientation so that after the assembly, the deviation of both parties can be partially offset.
The purpose of making two sets of directional signs is that the compensation for deviations can be considered comprehensively, even if the two-way bearing's respective rotation accuracy is improved, and the concentricity error of the seat hole and both end journals between the two bearings is obtained. eliminate. The surface of the mating surface is reinforced, such as sandblasting, and the inner hole is plugged with a slightly larger diameter plug to improve the mating accuracy.