Alternative to Shotpeening

[koza19]

I have a customer which we manufacture springs that get shotpeened and the customer is having issues with the shot media getting wedged in between the last active coil and closed coil. The spring is used in a hydraulic pump and they do not what any foreign material that could cavitate the pump. Does anyone know of a different shotpeening method that doesn’t use shot media?

 

[swall]

What size spring, and what is the spring material?

 

[koza19]

Material Chrome Silicon per ASTM A401
wire diameter range .125 to .250

 

[btrueblood]

I'd think any blasting media has the chance to leave residue behind, and residue in a hydraulic pump is a guarantee of failure. A better question might be "how to best clean these springs", and I'd be looking at ways to gently wedge open the final turn to ensure that area gets as well cleaned as the rest of the spring.

 

[swall]

Non shot peening options to investigate would included REM microfinishing, laser peening and nitriding. But, as btrueblood points, you might get more bang for your buck with an enhanced cleaning process.

 

[koza19]

Thanks for the info guys. Currently we are cleaning it exactly
like as btrueblood stated. Customer likes this method but does not want to pay for it. I would like to try to redesign the springs so they would not need to be shotpeened, this maybe the easier route.

 

[btrueblood]

"I would like to try to redesign the springs so they would not need to be shotpeened"

Well, probably not acceptable to the customer, as the fatigue life would suffer.

But how about redesigning the spring so that the last turn is not "fully closed", i.e. doesn't rest against the next turn? If the spring is guided in its travel, it is unlikely that the fully closed condition is a design requirement.

 

[koza19]

btrueblood sounds like a great idea I will recommend that to them. Sounds like an easier solution.

Thanks again

 

[btrueblood]

You're welcome, good luck.

 

[unclesyd]

Aside from the above recommendations I believe you have two other approaches to resolving your problem. First would be to look at changing shot size. The second would be to slightly stretch the spring while peeing with fixturing.

Here is paper with a little information on shot size.

http://www.ervinindustries.com/DocumentLibrary/TechnicalBulletin/EffectiveUse/EffectiveUse003.pdf

 

[unclesyd]

A play on my post concerning shot size.
You might want to check out the Badger Metal site. They use fine penning or nitriding or combination of the two to improve tool life.

http://www.badgermetal.com/extras/extras.htm

 

[WillCole]

I know this is way late... but did you look into nitriding?

 

[koza19]

Thanks again for the info everyone

 

[flash3780]

I'm not sure if you're still looking for alternatives, but have you looked into laser shock peening?

 

[koza19]

flash3780
Do you know anyone in the Chicago-land area that does laser shock peening? Also do you where I can find any literature about the process?


Thanks for the info

 

[israelkk]

Why not just use preset?

 

[koza19]

israelkk
We performed life cycle testing with just presetting the springs and could not achieve 10mm life cycles.

 

[israelkk]

It depends how deep is the preset. How do you control the depth of the preset?

 

[israelkk]

Can you give more detailed information of the spring:
Dimentions
First load point
Second load point
Number of active and total coils
Type of ends
Material specifications

Did you check wire surface conditions after coiling (Nicks, Scratches, Dents, Tool markings, etc.?

 

[prdave00]

Info on laser peening:

http://www.metalimprovement.com/laserpeening.php

You might also want to search the library at ShotPeener.com.

I looked into laser peening as an alternative to shot peening, but the cost was day and night compared to shot peening.