How to choose the high performance bearing of machine tool correctly? Following the Custom Hanger Bearing Units manufacturer.
Spindle bearing selection
The accuracy of the bearing used on the spindle of the machine tool should be ISOP5 or above (P5 or P4 is the accuracy grade of ISO, usually ranging from low to high (P0, P6, P5, P4, P2). For the spindle support of high-speed and high-precision machine tools such as CNC machine tools and machining centers, the accuracy of ISOP4 or above should be selected. Spindle bearings include angular contact ball bearings, tapered roller bearings, and cylindrical roller bearings.
1. As for the contact Angle of angular contact ball bearing, 15 and 25 contact angles are more popular at present; Generally, the contact Angle of 15 has a relatively high rotational speed performance, while the contact Angle of 25 has a higher axial bearing capacity. Due to the choice of preload on the application of precision angular contact ball bearing is very big, such as in high load, high rigidity occasions, usually choose the medium or heavy bearing preload; For some applications with high speed and high precision, it is necessary to select the appropriate preload in the early selection of bearing. Metal processing experts said that the preloading is generally divided into light, medium and heavy three, general light preloading is more common. In order to facilitate the use of customers, several major bearing manufacturers in the world are generally provided with pre-grinding bearing face and preload bearing, which is commonly known as universal matching precision angular contact ball bearing form. This type of bearing eliminates the customer's pre-load adjustment, thus saving installation time.
2. Precision cylindrical roller bearing
In the application of machine tool spindle, double-row precision cylindrical roller bearing will also be used, usually with precision angular contact ball bearing or thrust bearing combination. This type of bearing can withstand large radial loads and allow a high speed of rotation. The two rows of rollers in the metalworking on-line bearings are arranged in a cross way, and the wave frequency during rotation is greatly higher than that of the single-row bearings, and the amplitude is reduced by 60%-70%. This kind of bearing usually has two forms: NN30, NN30K two series bearing inner ring belt edge, outer ring can be separated; NNU49, NNU49K two series bearing outer ring with edge, inner ring can be separated, where NN30K and NNU49K series inner ring for cone hole (taper 1:12), with the spindle taper journal, axial movement of the inner ring, can make the inner ring swell, so that the bearing clearance can be reduced or even pre-tight bearing (negative clearance state). Cylindrical bore bearings are usually hot-packed, with interference fit to reduce clearance, or preloaded. NNU49 series bearings can be separated from the inner ring. Generally, after the inner ring is mounted on the spindle, finish the raceway to improve the spindle rotation accuracy.
3. Precision taper roller bearing
In some heavy-duty machine tool applications with certain requirements on speed, such as forging waste grinding, oil pipeline turning machine, heavy lathe and milling machine, the choice of precision taper roller bearing is an ideal scheme. Because the roller of tapered roller bearing is designed with linear contact, it can provide high rigidity and bearing capacity for the spindle. In addition, tapered roller bearing is a pure rolling bearing design, which can reduce the running torque and heating of the bearing very well, thus ensuring the speed and accuracy of the spindle. Since tapered roller bearings are capable of adjusting axial preload (clearance) during installation, this allows customers to better optimize clearance adjustment throughout the life of the bearing.
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