Selection of the mill bearing and assembly analysis

2020 - mill bearing selection and assembly analysis 07 - 20 Zhou Yanbo xin-hui wang abstract: the mill have bearings on both ends of the vertical shaft, is located in the upper end of the lower pulley and rotor respectively. Lower rotor bearing in motor driven at high speed, the circumferential force under the bearing, the belt tension and the gravity of the whole rotor ( Hierarchical impeller) Lock, bearing damage easily, bearing, outer deformation, etc. Two bearings due to factors such as assembly, sealing, lubrication, after making the grease gets hot dry friction caused by the liquid loss or leakage, quickly made bearing damage. Through the failure phenomenon in-depth analysis and research, find out the cause of the problem, for this problem was improved, thoroughly solved the problem of the mill bearing damage easily. A, thin wire mill working principle and structure of vertical impact crusher is the use of high speed movement when the kinetic energy of the material for crushing, the crusher work, high-speed rotating rotor material after feeding spiral into the crushing chamber, the rotor is accelerated rapidly, within its acceleration can reach hundreds of times the acceleration of gravity, on the impact to the tooth plate under the action of centrifugal force, so shattered by the tooth impact, friction, and material combination, such as the impact between the pieces. Second, the failure phenomenon of crusher have bearings on both ends of the vertical shaft, location is near the lower end of the belt pulley a, near the top of the rotor. Lower rotor bearing in motor driven at high speed, the circumferential force under the bearing, the belt tension and the gravity of the whole rotor ( Hierarchical impeller) , bearing damage easily ( Bearing lock, outer deformation, etc. ) 。 Bearing, bearing 2 3 due to factors such as assembly, sealing, lubrication, the grease gets hot after the dry friction caused by the liquid loss or leakage, quickly made bearing damage. Three, improvement measures 1, bearing type selection by the mechanical structure design of common sense, the bearing under 1 in addition to withstand normal circumferential force and tension of belt, the gravity of whole rotor also will have to be borne by the bearing, so only can bear radial force of deep groove ball bearing and only can withstand the axial force of the thrust bearing are not suitable for use, should choose to bear axial force and radial force of angular contact ball bearings ( Here for vertical installation of angular contact ball bearings can not to use, the bearing axial clearance can be preloaded by the gravity of the rotor and spindle, can achieve high rotation accuracy) And bearing on 4 because only bear radial force, can choose low price, high rotating accuracy, high limit speed of the deep groove ball bearings. Under our rotor bearing 1 with 6205 deep groove ball bearings, the radial dynamic load rating cr: 14 / KN; Radial static load rating cor: 7. 85 / KN; Grease lubrication, rated speed 13000 r/min; Oil lubrication, rated speed 15000 r/min. Suggestions for angular contact ball bearing 7205 ac, its radial dynamic load rating cr: 15. 3 / KN; Radial static load rating cor: 9. 5 / KN; Grease lubrication, rated speed 15000 r/min; Oil lubrication, rated speed 19000 r/min. 2, the correct bearing assembly requirements of the bearing assembly is also one of the important factors affecting the service life of bearing. To reduce or avoid bearing abnormal fever, problems in practical production, assembly, and in the design of shaft and hole, installing a bearing need to pay attention to some aspects of the content, in case of bearing abnormal fever. 2. 1 match for bearing ring and shaft with appropriate USES interference fit, not allowed to use loose or transition fit clearance fit; Outer ring and bearing hole with unfavorable use interference fit, and recommends the transition fit tighter. Both ring and outer ring, are not allowed to and connected with the relative rotation between shaft and hole ( Bearing 3, bearing and have therefore cause damage) , or bearing would be severe fever, light damage to the bearings, or burn out shaft and damage to the mill. Such as axis, unprocessed qualified, hole size must take remedial measures, such as excessive machining after must be boring again after repair welding, machining qualified before assembly. 2. 2 alignment requirements of bearing hole alignment has direct influence on the normal operation of high-speed bearing. Practice has proved that when using the 7205 ac Angle bearing ( Precision level for P5) And 6205 deep groove ball bearings ( Precision level for P5) Used ( The distance between the two bearings for 300 mm) When the axiality deviation in 0. 6 mm, under the condition of spindle rotation speed is 4200 RPM, deep groove ball bearing is run only a few minutes heat damage. Therefore, for speed, the higher the bearing, the alignment, the smaller the deviation should be suggested that control in 0. 01. When the coaxial degree have slightly out-of-tolerance can switch to a larger radial clearance of the bearing to offset part of axiality deviation. 3, grease seal mill bearing 2, 3, in the process of production in the deep groove ball bearing burn out many times, after repeated analysis reason, suspected to be used by bearing grease too thin, single bearing with dust cover on the sealing of the grease is not good, cause loss of grease bearing heating. Recommend replacing high dropping point of lubricating grease and use double sided with RD of axial labyrinth sealing device type deep groove ball bearings. Through the mill in the production process, and then four bearing damage, from theoretical analysis to the concrete practice to find the main cause of this problem and the solution. Through the selection of bearing, seal, lubrication and installation requirements of the four aspects of the research and analysis, put forward to solve grinder spindle bearing of low-cost long-term oil seal, points out the main reason for the high speed heavy-duty bearing fever and solution, fundamentally solve the problem of the mill bearing damaged, reduce the equipment failure rate, so as to ensure the continuity of silk processing technology process. （ Source: feed the heavens and the earth)