Steinmeyer Ball Screws

51 DE F I N I T I ONS A: Shaft cross section [mm 2 ] α : Coefficient of thermal expansion [1/°C] c: Lead compensation C 0a : Static axial load capacity [N] C a : Dynamic axial load capacity [N] C aerf. : Required dynamic axial load capacity [N] ∆ l b/t : Axial elastic deformation due to external load F i [µm] ∆ l b/t,pr : Axial elastic deformation due to preload F pr [µm] ∆ l p : Elongation of the shaft [mm] ∆ l T : Thermal expansion [mm] d N : Nominal diameter [mm] DN: Driving speed value [mm/min] Δt: Temperature increase [°C] „E": Tolerance of the cumulative lead error (JIS) E: Elasticity modulus [N/mm2] ε: Elongation relative to length e 0a : Mean lead deviation over entire travel l u e 2π : Lead error in one revolution (JIS) e 300 : Lead error in 300 mm (JIS) e p : Tolerance for the average lead deviation over entire travel l u e sa : Actual lead deviation over entire travel l u F i : External load [N] F i *: Modified external load [N] F m : Dynamic equivalent load [N] F m* : Modified dynamic equivalent load [N] F pr : Preload [N] F T : Tensioning force [N] i: Number of ball circles JIS: Japanese Industrial Standard k: Support coefficient (critical speed) L 10 : Nominal life 90% reliability [revolutions] l s : Unsupported shaft length [mm] l u : Travel [mm] m: Support coefficient (buckling] n i : Speed [rpm] n k : Critical speed [rpm] n m : Equivalent Speed [rpm] n max : Maximum Speed [rpm] P: Lead [mm] P B : Buckling load [N] P i : Load capacity per ANSI [lbf] q i : Time percentage [%] R b : Axial bearing rigidity [N/µm] R nu,ar : Actual nut rigidity [N/µm] R s : Shaft rigidity [N/µm] R t : Rigidity of ball screw [N/µm] T: Travel compensation (JIS) T pr : Preload torque v 2πa : Lead fluctuation in one revolution v 300a : Lead fluctuation in 300 mm v 300p : Tolerance of the lead fluctuation in 300 mm v ua : Lead deviation over entire travel lu v up : Tolerance of the lead deviation over entire travel l u

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