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Installation method of motor bearing and preparations before installation

by:JNSN     2022-03-13
Installation environment of motor bearings Bearings should be installed in a dry and dust-free room as far as possible, and should be kept away from metal processing or other equipment that produces metal chips and dust. When the bearing must be installed in an unprotected environment (as is often the case with larger motor bearings), appropriate measures must be taken to protect the bearing and associated components from contamination such as dust or moisture until the installation is complete. Preparation of the bearing Since the bearing is rust-proof and packed, do not unpack it until it is installed. In addition, the anti-rust oil coated on the bearing has good lubricating performance. For general-purpose bearings or bearings filled with grease, it can be used directly without cleaning. But for instrument bearings or bearings used for high-speed rotation, the anti-rust oil should be washed away with clean cleaning oil. At this time, the bearing is easy to rust and cannot be placed for a long time. Preparation of installation tools The tools used for installation should be mainly made of wood or light metal products, and other things that are easy to generate debris should be avoided; the tools should be kept clean. Inspection of the shaft and housing Clean the shaft and housing to confirm that there are no scratches or burrs left by machining, if any, use whetstone and fine sandpaper to remove them. There must be absolutely no abrasives (SiC, Al2O3, etc.) sand, chips, etc. in the housing. Next, check whether the size, shape and processing quality of the shaft and the housing conform to the drawings. As shown in Figures 1 and 2, measure the shaft diameter and housing bore at several locations. Carefully check the fillet size of the bearing and the housing and the verticality of the shoulder. In order to make the bearing easier to assemble and reduce the collision, before installing the bearing, apply mechanical oil to the mating surfaces of the shaft and the casing that have passed the inspection. Classification of bearing installation methods The installation methods of bearings vary depending on the type of bearing and the matching conditions. Since most of the shafts are rotated, the inner ring and the outer ring can use interference fit and clearance fit respectively, and when the outer ring rotates, the outer ring uses an interference fit. When using interference fit, the bearing installation methods can be mainly divided into the following types, as shown in the following figure. The most common method is to cool the bearing with dry ice, etc., and then mount it. At this time, the moisture in the air will condense on the bearing, so it is necessary to take appropriate anti-rust measures. It is suitable for bearings with large interference or interference fit on the inner ring of large bearings. Bearings with tapered holes are installed on a tapered shaft with sleeves. With nuts, it can be installed with a hand hammer if necessary. When the bearing has an interference fit of the inner ring and is installed on the shaft, pressure must be applied to the inner ring of the bearing; when the bearing is installed on the housing with an interference fit of the outer ring, pressure must be applied to the outer ring of the bearing; When the rings are all interference fit, a backing plate should be used, so that the pressure can be exerted on the inner and outer rings of the bearing at the same time. The shrink-fit method of heating the bearing to expand it and then installing it on the shaft can prevent the bearing from being subjected to unnecessary external force and complete the installation work in a short time. There are two main heating methods: oil bath heating and electric induction heating. The advantages of electric induction heating: 1) Clean and pollution-free; 2) Timing and constant temperature; 3) Simple operation. After the bearing is heated to the desired temperature (below 120°C), take the bearing out and put it on the shaft quickly. The bearing will shrink as it cools, and sometimes there will be a gap between the shoulder and the end face of the bearing. The bearing is pressed in the direction of the shaft shoulder. Installation of the outer ring When the outer ring is installed on the bearing housing with an interference fit, for small bearings, the outer ring can be pressed in at room temperature. When the amount of interference is large, it is pressed in by heating the bearing housing or cooling the outer ring. When dry ice or other coolants are used, the moisture in the air will condense on the bearing, and corresponding anti-rust measures must be taken. For bearings with dust caps or sealing rings, the heating temperature cannot exceed 80°C due to the pre-filled grease or sealing ring material, and the heating method cannot be heated by an oil bath. When heating the bearing, make sure that the bearing is heated evenly without local overheating.
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