Sheet metal Spring, Force to Compress To a smaller Diameter 2

[Zibraz]

I'm struggling to determine the force to reduce this sheetmetal spring to Ø17.8mm.

If someone could point me in the direction or give advice, that would be great. I can find alot about normal wire springs, but can't find much for a sheetmetal spring. The spring is 0.6mm thick and 10mm long.

Thanks!

 

[mfgenggear]

Op
How many, quantity?
Low volume 10 pcs, or 10000 parts.
This is a great brain teaser.
My thoughts and opinion.
Thus a very small part. I would first of make a new design.
OK but if you are set on this.
It will require developing.
Trial and error to allow for spring back.
A two or three stage die. Reason the leg
Pushed into the center.
Create the two small bends on b each end.
Then the large radii
Then bend the inner leg.
Depending on hardness, or tensile strength.
For small lot a small fixture with removable pins. Similar use for bending tubing.
HTH

 

[GregLocock]

@rothers was that a non linear contact analysis? Please could you plot the contact force?

 

[Stress_Eng]

Out of curiosity, I revisited the original method and updated it to be in-line with the polar method (same assumed forced radial displacement, point loading at start of contact not in middle of angular increment, etc). The result gives a bending stress of 196.7 MPa. Although it hasn't been checked, and as rothers has highlighted, the stress is close to FEA. Attached is the revisited file. Looks like this particular analytical method has been finalized!

 

[rothers]

My FEA is not great at post processing contact forces but for what it's worth here goes:

Reaction force contour plot:
Interestingly reactions concentrated in three places, sum of reactions are:
Left hand contact point = 15.37 N
Bottom contact point = 15.37 N
Right hand contact point = 14.33 N



Reaction Force Vector plot:
Ignore the exact position of the vector, it plots the vector start points at the final contact point of part 1 (the ring) but at the initial contact point of part 2 (the spring).
Anyway I'm sure you get the idea and is shows the directions nicely.


Make of this what you like !!