Page 1676 - MiSUMi 2025

[Technical Data]
Selection of Ball Screws 2

4. Allowable Axial Load
Allowable Axial Load is a load with a safety margin built-in against shaft bucking.
Axial load that applies to a ball screw needs to be less than Allowable 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.
•Allowable Axial Load (P)
n Q EI d 4 Allowable Axial Load Calculation Example
2
4
P＝ α＝m × 10 (N) Find the Allowable Axial Load for Fig.1
R 2 R 2
Where: <How to use>
P: Allowable Axial Load (N) · Thread shaft diameter F15, Lead 5
ℓ: Distance between Points of Buckling Load (mm) · Mounting method Fixed - Supportt
E: Young's Modulus (2.06×10 N/mm ) 2 · Distance between Points of Buckling Load ℓ1 820mm
5
I: Min. Geometrical Moment of Inertia of Across Root Thread Area (mm ) 4 · Screw Shaft Root Diameter d 12.5
Q
I＝ d 4 <Calculations>
64 m=10 since the mounting method is Fixed-Support,
d : Thread Root Diameter (mm) the Allowable Axial Load (P) is,
n,m : Coefficient Determined by Method of Screw Support d 4 12.5 4
P＝m ×10 ＝10× ×10 ＝3630(N)
4
4
Method of Screw Support n m R 2 820 2
Support-Support 1 5
Fixed-Support 2 10 Therefore, the axial load will need to be 3630N or less.
Fixed-Fixed 4 19.9 Table.1
Fixed-Free 0.25 1.2
: Safety Factor = 0.5
For higher safety, a higher safety factor should be required.
Distance between Load Acting Points(Buckling Load:Fixed-Fixed) ℓ1
•Figure1. Allowable Axial Load Curve
Screw Shaft Dia. Calculation Example
6 3 1.5 <Requirements>
3 5 · Distance between Points of Buckling Load
500mm
2 4 2 10 5 ø32 ·Mounting method Fixed-Support
1.5 4 3 2 1.5 5 8 6 5 ø25 ·The allowable axial load 10000N
Allowable Axial Load (N) 8 6 5 4 1.5 8 5 8 6 5 4 4 3 2 ø15 ø20 ➀Find the intersection between a distance of
10
<Calculations>
10
500mm between load acting points and the
axial load of 10000N (from the fixed-support
10
graduation). [Figure 1]
1.5
3
nearest to the intersection on the outside. The
shaft diameter can be a min. 15mm.
4 6 5 3 2 10 4 ➁ Read the shaft diameter of the diagonal line
2 ø10
3 1.5 8
1.5 10000N 6
2 10 4
10 3 8 4
8 1.5 6 3
6 10 4 5
5 8 4 2
4 6 3 1.5
3 5
4 2 10 3
10 2 1.5 2 3 4 5 6 7 8 9 10 3 1.5 2 3 4 5 6 7
Fixed- Fixed- Fixed- Support -
Free Fixed Support Support Distance between Points of Buckling Load (mm)
Method of Screw Support

B-031