323 "MMPXBCMF "YJBM -PBE Allowable Axial Load is a load with a safety margin built-in against a shaft bucking load. Axial load that applies to a ball screw needs to be less than Allowable Maximum Axial Load. Allowable Axial Load can be obtained by the following formula. Additionally, approximate Allowable Axial Load can be obtained from Table 1. Allowable Axial Load Graph. t"MMPXBCMF "YJBM -PBE 1 t'JHVSF "MMPXBCMF "YJBM -PBE $VSWF nπ2EI d4 P= = m ×104(N) ℓ2 ℓ2 Where: P: Allowable Axial Load (N) ℓ: Distance between Points of Buckling Load (mm) E: Young's Modulus (2.06×105N/mm2) I: Min. Geometrical Moment of Inertia of Across Root Thread Area (mm4) π I= d4 64 d : Thread Root Diameter (mm) n, m : Coefficient Determined by Method of Screw Support : Safety Factor = 0.5 For higher safety, a higher safety factor should be required. Method of Screw Support n m Support - Support 1 5 Fixed - Support 2 10 Fixed - Fixed 4 19.9 Fixed- Free 0.25 1.2 "MMPXBCMF "YJBM -PBE $BMDVMBUJPO &YBNQMF Find the Allowable Axial Load for Fig.1 <How to use> · Thread shaft diameter Ø15, Lead 5 · Mounting method Fixed - Support · Distance between Points of Buckling Load ℓ1 820mm · Screw Shaft Root Diameter d 12.5 <Calculations> g=15.1 since the mounting method is Fixed-Supported, the Allowable Rotational Speed (Nc) is, d4 12.54 P= m ×104 = 10 × × 104 = 3630(N) ℓ2 8202 Therefore, the rotational speed will need to be 3024rpm or less. Distance between Load Acting Points(Buckling Load:Fixed-Fixed) ℓ1 5BCMF 5 1.5 10 4 10 1.5 2 3 4 5 6 8 3 3 2 8 6 4 3 2 1.5 10 3 4 5 6 7 1.5 2 7 8 910 10 1.52 3 456 3 2 2 3 4 5 6 8 1.5 2 3 4 5 6 8 10 1.5 4 5 6 8 10 1.5 2 3 4 5 6 8 10 6 5 4 3 2 1.5 3 4 5 6 8 10 1.5 2 3 2 1.5 8 6 5 4 3 10 10000N ø32 ø25 ø20 ø15 ø10 10 Support -Support Fixed-Support Fixed-Fixed Fixed-Free Method of Screw Support Distance between Points of Buckling Load (mm) Lead (N) 4 3 5 4 4 5 4DSFX 4IBGU %JB $BMDVMBUJPO &YBNQMF <Requirements> · Distance between Points of Buckling Load 500mm · Mounting method Fixed - Support · the max. axial load 10000N <Calculations> (1) Find the intersection between a distance of 500mm between load acting points and the axial load of 10000N(from the fixed-support graduation).[Figure 1] (2) Read the shaft diameter of the diagonal line nearest to the intersection on the outside. The shaft diameter can be a min. 15mm. Ball Screws Selection of Ball Screws 2
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