super precision bearings

LIFE CALCULATION FOR SUPER PRECISION BEARINGSModified Life Calculation L hna20105I2a 23II K=010.50.2K=1K=2K=3K=4K=5K=6II0.10.05 0.1 0.2 0.5 1 2 5 10νκ = ν1IIIZoneI: Transition to endurance strengthCondition: Utmost cleanliness inthe lubricating gap and no excessiveloadsII: Good cleanliness in the lubricatinggapLubricant with suitable additivesIII: Unfavourable lubricating conditionsContaminated lubricantUnsuitable lubricants20: Basic a 23II factor for determining the a 23 factorν operating viscosity of lubricant; ν 1 rated viscosityWhere K > 6, the a 23 factor must beexpected to be in zone III.In such a case, a smaller K valueand thus zone II should be aimedat by improving the conditions.CleanlinessThe cleanliness in the contact areaplays a very important role forprecision bearings as• the relative influence on life isvery large with the generallylightly loaded bearings• contamination greatly promoteswear.It is therefore necessary to specifya cleanliness level that permitscontamination less than specifiedby factor V = 1. Reference valuesfor the V factor have been adoptedfrom the hydraulic field andcan be obtained from Table 21.The cleanliness factor s can betaken from Diagram 22.a 23 is derived from the equationa 23 = a 23II · s.In practice, utmost cleanliness isensured when the bearings aregreased and protected with sealsFAG · 140