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Thread: Flat spring design questions

  1. #1
    Associate Engineer
    Join Date
    Apr 2017
    Posts
    1

    Flat spring design questions

    I donít have any experience designing flat springs, so I thought I would gather as much advice as I could regarding a current design.

    I modeled a basic version of the geometry to not show other IP involved. The red plate in the attached picture is fixed 304 or 316 stainless steel. The cyan parts are made of aluminum and 316 stainless steel. For simplicity, I just made those parts cubes to show how the spring works. These cyan parts need to be pushed toward the red part ending up with a compression force of somewhere between 15 Ė 20 lbs. Once they have moved to where the straight part of the spring almost bottoms out on the red plate, they will lock into place. But that spring force needs to be permanently maintained for decades if possible. And for reference, the height of the geometry shown is 1.5Ē.

    My design questions are the following:

    1. Material and material thickness. This is my main problem, and I am in completely personally unknown territory. I have been using annealed 1095 cut on a laser, formed by hand, and then tempered and quenched to blue tempered spring steel. I was trying .025 and .030 thickness, but that seemed to produce a lot more force than I thought it would to flatten that arc. I think I may need to try some smaller thicknesses, but that might prove difficult to form (there is some wacky geometry at the bottom of the spring that I did not show, but only affects the spring in that ). I also have to wonder if I could use a springy stainless steel as well. There is also the galvanization to consider between the spring, the aluminum, and the stainless, but maybe I should just have the spring coated in nickel?

    2. The shape of the spring itself. The two straight legs (that prevent the assembly from ever being squeezed too far, which is critical) and the arc seemed like a logical choice. However, there still seems to be a lot more force than I want to have to compress that shape. But maybe that is because I am not using the right material, the right thickness, or the right cutout distance in the flat for that run.

    Thanks for any input. Its been fun prototyping these, but I just donít know enough to optimize this part the ways it needs to be.
    Attached Images Attached Images

  2. #2
    Lead Engineer
    Join Date
    Aug 2013
    Location
    Houston TX USA
    Posts
    369
    For a lower force flat spring, thinner material or a narrower spring are probably your best options

  3. #3
    Project Engineer
    Join Date
    May 2015
    Posts
    64
    How about a redesign using coil springs and guides for the blocks?

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