According to SMI Handbook 1991:
k = E d 4 / (10.8 Nt D)
Where
E = Modulus of elasticity (MPa | psi)
d = Diameter of wire (mm | in.)
Nt = Number of total coils
D = Mean coil diameter (mm | in.)
k = Rate (N·mm/rev. | lbf·in./rev.)
You can handle the expression to get k per degrees of deflection...
Hi.
I have this compression spring:
d = 7.50 mm
Nt = 5.5 REF.
ID = 84 mm
L0 = 130.60 mm REF.
Material SAE 1070; Tensile strength Sut = 1410 MPa (reported by the wire supplier).
L1 = 94 mm; F1 = 422 N +/- 10 %; corrected stress: 260 MPa (18.4 % Sut)
L2 = 58 mm; F2 = 837 N +/- 10 %; corrected...
Dear Israelkk, you are OK. Rate and free length are not requirements, but reference information. The mandatory requirement is force at height of 26.50 mm: 362,4 N ± 10 %.
The ends are closed and ground. Please, see attached sketch.
I see your suggestion about unused deflection, and why it...
Hi, Israelkk.
The spring requirements are:
Material: ASTM A 227 class II
Wire diameter: 2,50 mm
Inner diameter: 9,20 mm
Bore diameter: 8,40 mm
Free length: 32,50 mm
Max. deflection: 6 mm
Total coils: 6
Rate: 60,4 N/mm
Ground
Use: in oil filters of cars
Static
Thanks by your help.
Best...
Thank you for your replies.
We are the spring maker. I need to answer to my boss if we must to suggest to the client to reduce the spring mass (no feasible by stress), to omit the presetting or to lookfor other cost reduction in manufacture line. We can't to buy a new fastest coiler machine...
Hello, Engineers.
Presetting is a process by the spring manufacturer in order to increasing the ability of the wire to withstand higher stresses.
The spring will be compressed to max deflection in the final device. So, is it allowable for the manufacturer omit this process? (Will lead the set...
And about this issue, Carlson says:
"SMI recommends a conservative and consistent use of the stress correction factor and advises the use of the Wahl formula"
Jh0an1
thread404-351326
Thank you very much to all by the help.
I just talked to my friend. The springs are working fine today.
I have gotten this information of Carlson, in Springs magazine, courtesy of Spring Manufacturers Institute, confirming your suggestions:
"When to Use:
The stress...
Hi, desertfox,
The initial tension of 83,2 N was obtained after the first sample, by experimental measurement. I had to estimated initially this characteristic in 32.2 N (the value suggested by SMI 1991 divided by 2 to consider the stress relieving). The springs of this automatic coiler machine...
Hi, israelkk,
Initial tension: force to begin the clearance between the coils.
Force to 147 mm: 150 N minimum
Force to 200 mm: 450 N around(according to equations of forces equilibrium applied by me)
The two springs doesn't give the same forces at 147 and 200 mm length because the first...
Hi, I'm a mechanical engineer from Venezuela. I'm helping to my friend with his seats factory. He need to improve an extension spring.
The current spring has the following characteristics:
- Material: EN 10270-1 Grade SM
- Tensile Strength, Rm: 1690 N/mm² minimum.
- Wire diameter, d: 2,50 mm...