Coil spring vs helical spring 1

[magnusswe]

Hi!
I am new to this field so... this is probably a stupid question!

I have just read about an impovment proposal of a weapon system. One of the improvements was to replace a coil spring with a helical spring! So, what is the difference, if any?

//Magnus

 

[israelkk]

Maybe they mean helical machined spring?

http://www.webspawner.com/users/israelkk/

 

[magnusswe]

Maybe... So, what would that mean?

 

[israelkk]

Instead of using a helical spring made of a coiled (round or rectangular section) wire you can make a spring from a metal rod machined in a way to create a helical spring with a rectangular wire section.

The main advantage is that the spring and its ends can be machined to any shape providing an accurate mean for assembling and holding. You can a create metal part with an integral spring. Some claim that the spring properties can be more accurate and repeatable (but to my opinion it will result in a great rice increase). This kind of spring is mainly find use in aerospace and military area where the spring price is only small part of the system price.

The disadvantage is that the price of the spring is much higher and it is not a mass production process. More than that, the metal properties of the coiled spring are superior because of the wire drawing process that orients the metal grains in the correct direction. When one machine the spring the metal grains are cut and are not optimally oriented.

One more issue is the special tooling needed if the space between the coils is very small such as in the case of a helical torsion spring. Then, the spring can be machined by a wire EDM process which is a very slow process and as a result a pricey process.

There are other issues such as pre or post heat treatment and distortions as the hydrogen embrittlement problems due to the wire EDM process but it is beyond the scope of this post.

http://www.webspawner.com/users/israelkk/