Expressions and Definitions

A

Shaft cross section [mm²]

i

Number of ball circles

α

Coefficient of thermal expansion [1/°C]

JIS

Japanese Industrial Standard

c

Lead compensation

k

Support coefficient, critical speed

C0a

Static axial load capacity [N]

L10

Nominal life 90% reliability [106 revolutions]

Ca

Dynamic axial load capacity [N]

ls

Unsupported shaft length [mm]

Caerf

Required dynamic axial load capacity [N]

lu

Travel [mm]

Δlb/t

Axial elastic deformation due to external load Fi [µm]

m

Support coefficient, buckling

Δlb/t,pr

Axial elastic deformation due to preload Fpr [µm]

ni

Speed [rpm]

Δlp

Elongation of the shaft [mm]

nk

Critical speed [rpm]

ΔlT

Thermal expansion [mm]

nm

Equivalent Speed [1/min]

dN

Nominal diameter [mm]

nmax

Maximum Speed [rpm]

DN

DN value [mm/min]

P

Lead [mm]

Δt

Temperature increase [°C]

PB

Buckling load [N]

"E"

Tolerance of cumulative lead error (JIS)

Pi

Load capacity per ANSI [lbf]

E

Elasticity modulus [N/mm²]

qi

Time percentage [%]

ε

Elongation relative to length

Rb

Axial bearing rigidity [N/µm]

e0a

Mean lead deviation over entire travel lu

Rnu,ar

Actual nut rigidity [N/µm]

e

Lead error in one revolution (JIS)

Rs

Shaft rigidity [N/µm]

e300

Lead error in 300 mm (JIS)

Rt

Rigidity of ball screw [N/µm]

ep

Tolerance of average lead deviation over entire travel lu

T

Travel compensation (JIS)

esa

Actual lead deviation over entire travel lu

Tpr

Preload torque

Fi

External load [N]

v2πa

Lead fluctuation in one revolution

Fi*

Modified external load [N]

v300a

Lead fluctuation in 300 mm

Fm

Dynamic equivalent load [N]

v300p

Tolerance of lead fluctuation in 300 mm

Fm*

Modified dynamic equivalent load [N]

vua

Lead deviation over entire travel lu

Fpr

Preload [N]

vup

Tolerance of lead deviation over entire travel lu