Distressed Nerd: Alternative to thin spring steel? 6

[DistressedNerd]

Figure out a solution and I will name my pet hamster after you.

Can anyone tell me a plastic or cheaper to manufacturer alternative to this design - 7'' diameter circle made out of spring steel wire that easily deforms and returns to circle shape. It needs to able to simply crumple it up in your hand and then release and it springs back to original shape.

Please see video for more information (in the video it is enclosed in fabric)- Link

 

[tbuelna]

The metal is called Nitinol.

Please start addressing your pet hamster as "Your Highness".

 

[Tmoose]

The star was mostly for the "your highness" part.

Dan T

 

[DistressedNerd]

Your highness - the question was for a plastic or cheaper to manufacturer alternative to this design.

 

[3DDave]

I see this is from someone with an electrical background. I'll trade you for a cheap way to make semiconductors out of plastic, preferably injection molded nylon. Being able to injection mold a functioning circuit board in one shot would be worth even more.

The guys who made that device are already using the cheapest material for the job.

 

[drawoh]

DistressedNerd,

You can do this with plastic if you make it very thin. How much force do you need to exert. Why does it have to be plastic?

--
JHG

 

[TheTick]

I assume from the lack of information in the OP that the part must last forever over an infinite number of uses. Or maybe just one time? Hard to tell. Plastic should work fine if you have absolutely no concerns about creep or fatigue, which are only imaginary constructs artificially formulated to make MEs look almost as smart as EEs..

 

[zifos]

Might try researching Urethane. It comes in all kinds of hardness levels from hard to really soft. I even found a website that sells urethane springs.

http://www.centuryspring.com/products/urethane.php

With a 7 inch OD and 6.9 ID one could probably smash it into a ball and have it return to it's original shape.
I'm guessing it won't perform exactly as the metal does (i.e. won't be as "snappy") but will probably be cheaper. Another design consideration, if you're concerned about imaginary constructs, is how long it will be held in the compressed state before being released. It should be cheap enough to just get a prototype made and play with it. Would also come with a ridiculous number of options for color, durometer, etc. and one could possibly have it impregnated with fibers of some sort to help achieve desired performance.

 

[dgallup]

You could use almost any elastomer.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[Nereth1]

I agree that some plastics could do this but they would probably not be remotely as stiff as doing it out of spring steel.

DistressedNerd, you mentioned you wanted it cheaper - are you aware that spring steel is actually pretty cheap stuff? Most of the time it's just high carbon steel with a heat treat. That particular arrangement might literally be straight spring steel wire passed through a loop of fabric, in which case you can literally buy meters of 0.5mm piano wire (so you don't have to organise the heat treat yourself), cut to length, feed it through and call it a day.

 

[gruntguru]

Nereth1 have you watched the video? You can't scrunch 0.5 piano wire to that extent and have it spring back.

How about a thin balloon inflated to the point just before it starts to swell?

Engineering is the art of creating things you need, from things you can get.

 

[Nereth1]

I had assumed that those disks literally just had spring steel inside because they give them out like candy so I assume they must be cheap - but perhaps I was wrong. Assuming they are indeed all nitinol, perhaps multiple loops of extremely thin spring steel could serve a similar function?

 

[tbuelna]

Your highness - the question was for a plastic or cheaper to manufacturer alternative to this design.

Maybe you can provide specific details of your existing spring design, such as cost, spring properties, load cycles, deflections when "crumpled", etc. so we don't have to guess at a possible solution. Since you did not provide a cost basis, how the heck would I know if Nitinol is cheaper or not?

All kidding aside, I don't think you'll find a cheaper metal alternative than common commercial spring wire alloys. As for "plastic" materials, the raw material cost of high-performance plastics is quite high. And there is also the significant non-recurring costs involved with plastic components for things like mold tooling. On the other hand, the tooling for wound steel wire springs is usually relatively cheap.

 

[3DDave]

Nitonol is special because it can be seemingly plastically deformed and will not spring back until a critical temperature is reached, at which point it returns to a previously set (at high temp) shape.

Sunshade disks do not use Nitonol. They don't usually use round wire either, but a flat strip of spring steel which uses the thinness of the section to produce the flexibility and the width of the strip to produce the desired loads.

Making something with decent 'spring-back' requires high elastic modulus to provide the springiness, and high strength to allow large deformations. Neither of these are characteristics of most plastics. Carbon fiber and fiberglass are suitable, except for the difficulty of joining. The spring-steel can be easily joined with a crimped sleeve and the torsion continuity is easy to maintain due to the rectangular section typically used. Without torsion continuity the strip doesn't snap back as hard.

 

[DistressedNerd]

Meet 3DDave everybody.

 

[Nereth1]

I feel like I need half marks for my answer. I didn't get the rectangular cross section but I got the material!

 

[DistressedNerd]

Agreed, Daveth it is.

 

[Nereth1]

Glad to have usurped myself some glory.

But hey Daveth actually rolls of the tongue! You could really name him that!

 

[DistressedNerd]

3DDave - I found what you're talking about in a collapsible laundry hamper (see image), but for the life of me I can't find where to get it in varying sizes (or hardly at all) - I am looking for somewhere I can buy small quantities to test. There has to be a technical name for it or something that I am missing that's producing 0 search results.

The laundry hamper strip of steel has these dimensions rectangular cross section dimensions - 0.1'' x .025''

 

[Nereth1]

If you can't find the heat treated steel off the shelf in a small quantity, it should be very cheap to get it made up at a custom spring place. The stock would presumably be available as that which is used for a flat torsion spring.