previous rfq page next index page home page 4 load bearing mechanisms load bearing mechanisms are the structural backbone of any linear/rotary motion system and are a critical consideration this section will introduce most of the more common types of load bearing mechanisms found in linear motion machinery in general bearings allow smooth low friction motion between two surfaces loaded against each other the motion can be either rotary such as in a turning shaft or linear such as a machine part moving back and forth some applications require that a bearing accommodate both types of motion simultaneously which is referred to as a combination bearing in both cases there should be a strong attempt to provide enough lubrication to keep the bearing surfaces separated by a film of oil the absence of physical contact provides most bearings with long service lives bearings are evaluated on the basis of how much load they carry at what speeds they can carry the load and how long they will serv
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previous rfq page next index page home page technical information rolling element bearings or roller bearings make up the bulk of commercially available and applied bearings these types of bearings rely on either balls or rollers to carry the load the rolling motion produces less friction than found in plain bearings for this reason roller bearings are also referred to as antifriction bearings both radial loads and thrust loads can be supported by this type of bearing lubrication is either permanently sealed in the bearing or is required during operation the largest causes of failure are either exceeding temperature load and speed limits or providing insufficient lubrication during operation since roller bearing applications often involve heavy loads and high speeds failure can be catastrophic extremely costly and time consuming to repair usually there will be an increase in the sound of the balls or rollers in the raceways when approaching failure there are many different configuratio
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previous rfq page next index page home page flat race flat seat bearings consist of two flat washers and a ball retaining assembly they are used when the ball retainer assembly must carry thrust loads without restraining shaft oscillations or flexures they work well with light loads and are very economical grooved race flat seat bearings are the most common type of thrust ball bearing they consist of a shaft mounted small bore washer a large housing mounted bore washer and a ball retaining assembly grooved race bearings have a load bearing capacity approximately 4 times greater than flat race bearings banded thrust ball bearings are self-contained have grooved races have a stationary and rotating face with full ball complement and are encased in a containing band these bearings are most commonly used where the bearing s outer circumference must be protected from contamination for blind installation or where separating forces cause substantial axial motion of bearing components alignin
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previous rfq page next index page home page technical information l l d3 d4 f1 ญญญ ญ ญญญ ญญญ ญญญ 4 2 d1 d2 l l d3 d4 f2 ญญญ ญญญ ญญญ ญ ญญญ 4 2 d1 d2 l l f3 ญญญ ญ ญญญ 4 2 d d ญญญ ญ ญญญ d d 3 1 4 2 1 information technical 14 d4 7 f3 f1 f4 d1 d2 f2 d3 llld3 d4 f4 ญญญ ญญญ ญญญ ญญญ 4 2 d1 d2 horizontal translation with side load when a side load is applied to the bearing system the loads on the individual bearings change and new equations are required each bearing will have a resultant normal load as well as a side load the orientation of the applied load with respect to the bearing system is the important feature to consider this means that these equations can still be used even if the orientation of the translation is not horizontal as long as the load to bearing relationship is preserved l d4 f1 f2 ญญญ ญญญ 2 d2 l d4 f3 f4 ญ ญญญ ญญญ 2 d2 l l d3 f1s f3s ญญญ ญญญ ญญญ 4 2 d1 l l d3 f2s f4s ญญญ ญ ญญญ ญญญ 4 2 d1 vertical translation with vertical load when the loa
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previous rfq page next index page home page roller bearings are also widely used in linear rotary motion applications there are several principal types of roller bearings in general they have higher load capacities than ball bearings of the same size due to the increased area of contact and except for the cylindrical type lower speed capabilities they are commonly used in heavy-duty moderate-speed applications and as with ball bearings there are many different styles to choose from because of the geometry roller bearings are not tolerant of shaft misalignment cylindrical roller bearing needle bearing caged crossed roller bearing cylindrical roller bearings have the highest radial load capacity for a given cross section and the highest speed capability for any given roller bearing type a common problem encountered is roller skidding which causes premature failure solutions include a slightly concave raceway that pinches the ends of the rollers or the use of hollow preloaded rollers to
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previous rfq page next index page home page technical information plain bearings rarely ever carry more than 3000 psi another way of determining a bearing s load capacity is through maximum pv factor this is the value of pressure on the bearing psi times the shaft speed feet/min f ญญญญญญญ derating factor d ญญญญญญ a a x 20ฐ fy 0ฐ fy 20ฐ 0.7 0.8 0.9 1.0 40ฐ 60ฐ 80ฐ force on single bearing force on double bearing series 1 bearings roller bearing selection load speed and shaft alignment are the most important features to consider when selecting roller bearings it is suggested that in the case of needle bearings the shaft parallelism be less than 0.0003 for the entire length of the bearing section further the shaft should be round to within 0.0002 or to within half the shaft tolerance 16 www.techno-isel.com angle of applied load a 1 information technical if the pv value for the application is less than the maximum pv value for the bearing considered and if the application pressure load d
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previous rfq page next index page home page selecting a linear bearing system there are several factors in selecting a linear bearing system here are the main items to consider ท travel ท load ท orientation nominal life expectancy the nominal life expectancy is achieved or exceeded a majority of 90 of the nominal life expectancy before the first indication of fatigue of material appears l c p lh ท maximum speed ท minimum acceleration ท environment oscillated movement with very small strokes rippling vibration during standstill rippling due to the variation in installations and operating conditions it is not possible to determine the exact usable life of a linear guide in advance the safest method to obtain a correct assessment of the usable life is to compare cases with similar installation x 1 833 h ท nosz c p cpxx 2 combined loading capacity f2 f1 f 4 lh 1666 v l [m lh [h c [n p [n x 3 h [m nominal life expectancy in 100,000 m nominal life expectancy in operating hours dyna
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previous rfq page next index page home page linear bearings application worksheet name phone linear motion application worksheet 1 information technical 18 company name fax address 1 address 2 city state zip brief description of application e-mail please use this area for any notes or diagrams max load max speed max accel travel complete cycle time environment woodshop cleanroom etc travel accuracy needed orientation of load format 1 2 3 see page 14 www.techno-isel.com
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