Storage and installation methods of machine tool spindle bearings
Whether the machine tool spindle bearing is installed correctly determines the life, accuracy and performance of the bearing. The steps to install the spindle bearing are as follows: a. First check the shaft and bearing seat b. Unpacking and cleaning c. Installation d Confirmation after installation 9.2.1 Inspection of the shaft bearing seat ● Fully clean the shaft and bearing seat to remove dust or debris. Also check for cracks and burrs. ● Check and record whether the dimensions of the shaft and the bearing seat, and the verticality and roundness of the shaft shoulder meet the requirements of the drawings. As shown in Figure 9.1, measure 2 positions in the axial direction and 4 positions in the circumferential direction. ● Figure 9.1 Measuring position of shaft diameter and inner diameter of bearing housing 9.2.2 Unpacking and cleaning ● Please do not open the package before using the bearing. Please wear latex gloves when unpacking. Opening the bearing package without wearing latex gloves can cause dust to enter the bearing or cause rust. ● The surface of the unpacked bearing is coated with anti-rust oil. Please use kerosene or clean gasoline for cleaning. When cleaning, use a spray with a filter or use a rough washing tank and a fine washing tank with a metal mesh at the bottom of the tank for cleaning. ● Cover the cleaned bearing with a dust cover after degreasing. Do not rotate the degreased bearing. Use of bearings 9-1 Storage and transportation of bearings. Spindle bearings are precision parts. Therefore, be careful to prevent damage caused by vibration. Care should also be taken to prevent dirt or rust during storage and transportation. ● The bearing should be stored in a cool and dry place away from direct sunlight. ● Do not place the bearing directly on the ground. The bearing should be stored on a shelf 30cm above the ground to prevent dust accumulation. ● Inventory management should be first in, first out. At the time of shipment, the product with an earlier packaging date will be shipped. ● When handling the bearing, be careful to collapse or fall. Avoid bearing damage due to impact. Deformation or damage to the package causes dust to enter. Generally, the bearings installed on the machine tool have interference fit on the shaft and clearance fit on the bearing seat. There are thermal expansion method and press fitting method to install the bearing on the shaft. Thermal expansion method is a method in which the bearing is heated and expanded above the interference between the shaft and the inner ring. Using an induction heater with a demagnetization device (Figure 9.2) or a heating bath can not impose undue stress on the inner ring and shorten the operating time. The heating temperature must not exceed 120 degrees. Otherwise it will reduce the hardness of the bearing steel and shorten the life of the bearing. When the heated bearing is installed on the shaft, the axial direction will shrink after cooling, and there will be a gap between the inner ring and the shaft shoulder (Figure 9.3). Use a nut to lock it. [Press-fitting method] Use a clamp to hold the end face of the inner ring and press into the shaft with a press or jack (Figure 9.4). Do not apply force to the outer ring or cage when the inner ring is pressed in. Especially when installing angular contact ball bearings, applying force to the opposite direction of the contact angle will cause damage to the track shoulder and the ball. Please avoid it (Figure 9.5). ● Fig. 9.4 The ball may be damaged by pressing the inner ring ● Fig. 9.5 Mounting direction of angular contact ball bearing Reference: The maximum radial runout position is marked on the end face of the maximum radial runout position of the outer ring and the inner ring. Align the minimum shaft runout position with the marked position on the inner ring to minimize shaft runout. The same is true for the outer ring, and the minimum runout position of the bearing seat must be aligned with the marked position of the outer ring. In addition, the V mark position of the outer ring has nothing to do with the position of the assembly indication of the outer diameter surface. Maximum radial runout image ● Figure 9.6 Maximum radial runout position reference: Installation and disassembly force The force required to press the inner ring of the bearing into the shaft (medium solid) or disassembly is different due to the interference or the degree of shaft machining, but the formula can be used 9.1 Approximately calculated. (Formula 9.1) Ka: Press fit force or disassembly force (KN) fk: Coefficient under different installation and disassembly conditions (Table 9.1) Δde: Effective interference (mm) B: Inner ring nominal width (mm) d: Bearing nominal inner diameter (mm)di: Average outer diameter of inner ring (mm) Cylindrical roller bearing. For other bearings, here D: Nominal outer diameter of bearing (mm) ● Table 9.1 Coefficient conditions for different installation and disassembly conditions fk (average value) Inner ring pressure Insert the cylindrical solid shaft 39 and pull out the inner ring 59 from the cylindrical solid shaft. Note) This value is the value when the bearing inner diameter and the shaft surface are coated with a thin layer of lubricant.