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9Dimensioning Frictionless Tables9.1 Load Carrying Capacity andOperational LifeIn applying frictionless tables, the primary consideration is the relationship of the appliedload to the load carrying capacity. The elastic deformation (rigidity) must also be evaluated.The load carrying capacities of the individual frictionless tables are based on the fundamentalsestablished by ISO and DIN for the calculation of roller bearings (ISO 281, for NDNDIN 636, part 3). The load carrying capacity C is the load with which a nominal operationallife of 100 000 m travel is achieved, given that the size and direction of the load remainunchanged and the line of application is vertical onto the frictionless table surface.By definition, the latest research results have shown that the static load should not begreater than the dynamic load. The reason for this lies in the fatigue behavior which isalways initiated at the highest loaded point. In the case of an absolutely constant loadduring standstill and in operation, the fatigue process will start at that point where the staticload is present longest. The C-values given are used in the operational life equation tocalculate the operational life resulting with a given load.The operational life is the travel in metres which is made by a frictionless table before thefirst signs of metal fatigue appear on any of the anti-friction guideway components. TheB 10 operational life is achieved when 90% of a statistical sample of frictionless tables meetor exceed the prescribed amount of travel.Dynamic loading capacity CAs previously mentioned, the load carrying capacity C is based on an operational life of100 000 m. Some manufacturers use, for various reasons, a larger load carrying capacitywith 50 000 metres operational life. The C 50 values for SCHNEEBERGER frictionless tablesare calculated as follows:C 50 = C • 1.23 for frictionless tables with rollersC 50 = C • 1.26 for frictionless tables with ballsLife ExpectancyAccording to the DIN and ISO standards, the load carrying capacities for roller bearingsare given in such a manner that from the operational life equation a value results which,with 90% probability, will be exceeded. Should this probability not suffice, then theoperational life must be shortened with the a 1 factor per the following tables:LifeExpectancy % 90 95 96 97 98 99a 1 1 0.62 0.53 0.44 0.33 0.21• 34
LINEAR TECHNOLOGYOperational life calculationThe operational life L, the dynamic load carrying capacity C (N) and the loading P (N) havethe following relationship:9.2 Moment LoadingL = a 1 ( C Pwhereby a is the probable life expectancy factor. The operational life in hours can be calculatedwhen the single stroke H (m) and the time needed for it t (s) are known:L • tL h in hH • 3600) 10/3 • 10 5 m for rollers and needlesL = a 1 ( C P ) 3 • 10 5 m for ballsIn addition to the load carrying capacity C,you will find in the tables of dimensions forthe individual frictionless tables the permissiblevalues for moment loading. M L is themaximum possible torque lengthwise andM Q the maximum possible torque crosswise.StraightnessTravelDimensioning Frictionless Tablesof Travel Yaw/M LRoll/M QPitch/ M LFlatnessof Travel• 35
Page 1 and 2: LINEAR TECHNOLOGYSLIDESDynamic and
Page 3 and 4: 1Product OverviewFrictionless Table
Page 5 and 6: 2Applications2.1 Die Attach System
Page 7 and 8: 2.3 Printed Circuit BoardAssembly w
Page 9 and 10: 3Frictionless Tables Type NKLINEAR
Page 11 and 12: LINEAR TECHNOLOGYLayout of the stan
Page 15 and 16: 4Frictionless Tables Type NKLLINEAR
Page 21 and 22: 5.5 SpecificationsOrder No.Dimensio
Page 23 and 24: 6Micro Frictionless Tables Type NDN
Page 27 and 28: LINEAR TECHNOLOGYStraightness of Tr
Page 29: 8Design and Fitting GuidelinesLINEA

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