COMPRESSION SPRING CALCULATOR (LOAD BASED DESIGN)

INPUT PARAMETERS
Design Type	One Load & Free Height One Load & Spring Rate Two Loads
DIMENSIONAL PARAMETERS
Parameter		Value
Wire diameter [d]			mm m inch ft
Spring outer diameter - [OD] Spring mean diameter - [D] Spring inner diameter - [ID]
Spring free height (length) [Lf]
Height 1 [L1]
Height 2 [L2]
Load 1 @ height 1 [F1]			N kN lbf
Load 2 @ height 2 [F2]
Spring rate [k]			N/mm lbf/inch lbf/ft
End types for compression spring
Plain (Open) Plain (Open) and Ground Squared (Closed) Squared (Closed) and Ground
SPRING MATERIAL &  STRESS RELEATED PARAMETERS
Parameter		Value
Material selectionx		User defined Music Wire Hard-drawn wire Chrome-vanadium 302 Stainless wire Phosphor-bronze wire Oil tempered
Elastic modulus [E]			GPa psi*10^6
Poisson's ratio [v]			---
Material tensile strength [Sut]			MPa psi ksi
Prestressing (Set romoval)
Unprestressed (Set Not Removed) - Default Prestressed (Set Removed)
Allowable torsional strength  (% of Sut) +			%
Design factor at solid height against torsional stress [ns]			---
SPRING STABILITY (BUCKLING)
Parameter		Value
Spring stability (buckling) check	Stability control
End condition*
Ends are fixed with flat parallel surfaces One end flat & fixed, other end pivoted (hinged) Both ends pivoted(hinged) One end clamped, one end free User Defined
End condition constant [α]			---
Design factor for buckling [nb]			---

Note 1 : ^x Spring material properties are from Ref-2 except "User defined" selection.

Note 2 : ⁺ Equals maximum allowable torsional stress in static applications. See supplements for reference values.

Note 3 : * Ends supported by flat surfaces must be squared and ground [Ref-2] .

RESULTS
DIMENSIONAL PARAMETERS
Parameter		Value
Number of active coils [Na]		---	---
Number of total coils [Nt]		---
Spring index [C*]		---
Spring rate [k]		---	N/mm lbf/inch lbf/ft
Wire diameter [d]		---	mm m inch ft
Spring outer diameter [OD]		---
Spring mean diameter [D]		---
Spring inner diameter [ID]		---
Outer diameter at solid length [ODat solid***]		---
Spring free length (height) [Lf]		---
Spring solid height [Ls]		---
Maximum deflection (Lf to Ls) [Δx]		---
Pitch at free length [p**]		---
SPRING MATERIAL &  STRESS RELEATED PARAMETERS
Parameter		Value
Load at solid height [Fs]		---	N kN lbf
Shear stress at height 1 [τ1]		---	MPa psi ksi
Shear stress at height 2 [τ2]		---
Shear stress at solid height [τs]		---
Ultimate tensile strength of material [Sut]		---
Allowable torsional strength [Sall ]		---
Factor of safety against torsional yielding at solid height [foss (Sall / τs )#]		---	---
Modulus of rigidity [G]		---	GPa psi*10^6
Elastic modulus [E]		---
Material ASTM No.	---
SPRING STABILITY (BUCKLING)
Parameter		Value
Stability condition (includes nb)		---
Factor of safety against buckling [fosb+]		---

Note 1 : * The preferred spring index range is 4 to 12 according to [Ref-1] . Compression springs with high indexes tangle and may require individual packaging, especially if the ends are not squared. Springs with indexes lower than 4 are difficult to form [Ref-1] .

Note 2 : ** According to no yielding assumption and L_f length shall be same after loading.

Note 3 : *** Does not include the effect if the spring ends are allowed to unwind.

Note 4 : ⁺ Shall be larger than the design factor for buckling (n_b ≤ fos_b )

Note 5 : ^# Shall be larger than the design factor at solid height  (n_s ≤ fos_s )

Force vs Spring Height

Shear Stress vs Spring Height

Note 1 : The load deflection curve for helical compression springs is essentially a straight line up to the elastic limit, provided that the amount of active material is constant. The initial spring rate and the rate as the spring approaches solid often deviate from the average calculated rate. When it is necessary to specify a rate, it should be specified between two test heights which lie within 15 to 85 % of the full deflection range. [From Ref-1]