"adjusted"? compression springs

[foxtrot]

Something I've done, and watched done many times in prototypes etc. is to "stretch" (permanently deform)a compression spring a bit to increase it's load at a specific deflection. My question is -- what effect does this have on other spring characteristics, particularly life? Would it actually be acceptable to adjust a stock spring to a specific application if the stretch was done in some repeatable manner?

Thanks in advance.

 

[israelkk]

This is the worst you can do to a spring. Many high quality springs undergo a process called "preset", "set remove" or "scragging". This process induces residual favorable shear stresses into the spring wire when it is manufactured. This process makes the spring "stronger" and reduce the chance for relaxation.

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

 

[desertfox]

Hi foxtrot

I have never seen compression springs stretched after manufacture my understanding of pre-set or scragging is that you deliberately manufacture your spring longer than is required then you compress the spring to solid several times.
Cutting a long story short this sets up a favourable residual stress within the spring that allows higher design stresses than otherwise would be possible with an identical un - scragged spring.
A word of caution here is that this treatment is mainly used
on springs of static duty.
"spring design" by W.R.Berry is a very good reference to obtain more info on scragging.

regards

Desertfox

 

[israelkk]

desertfox

Just a small correction.

The scragging is not just for static. What Berry means is that even if you do scragging you should take the full Wahl correction factor even for static application. He argues with others in the USA that for static application allow to take a reduced Wahl factor. If the spring is for cyclic application then you should use the full Wahl correction factor.

From my experience I agree with Berry as for springs made for cyclic applications but for springs for static application I do sometimes use the reduced Wahl factor but if it is possible and fit the situation.

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

 

[foxtrot]

Thanks to all for the input.

IsraelKK: I went to the URL on your reply--Imagine my surprise when I found that The Ultimate Spring Designer was still available--I bought my copy 10 + years ago from the person who (I believe) wrote and developed the program --it's really a terrific piece of work and has seen use numerous times over the years. I occasionally have checked the web over the years to see if it had ever been updated to a Windows environment but never found anything about the program at all. Now I learn that the version that's still available is apparently the same rev as mine (2.0). Any plans to update it in the future? -- The only problem that I have encountered running in a DOS window in XP Professional is that it won't talk to my printer. Any suggestions as to what I might be doing wrong or is this to be expected? at any rate it's still fully functional and even without the printing--I'd recommend this program to anyone interested in a spring design. Hope you are encountering success with the sales.

 

[israelkk]

foxtrot

Yes I am the one that developed the program. It is always a pleasure to here positive responds from old customers. Now a day people dismiss anything that is DOS based program and thereby they miss the opportunity to get a hold on what you yourself define as a "terrific piece of work".

As for the printing issue, the printers today do not support what used to me "IBM printer" in order to save money and they usually are "Windows version printers".

The solution to the printing issue is very simple. I hope you know that you can Mark, Select and copy the text from a DOS screen from which appears inside Windows screen. Then just paste it into Microsoft Word or Notepad or any other Windows based editor or Word processor.

To mark and select just click the little C\: square on the top left of the DOS window and select Edit Mark and use the mouse to drag and select the text.

You are not the first to ask about a Windows version but it is not economically justified.

Today I mostly do consulting using this program and other programs I developed since this program was introduced back on 1986.