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Alternative to Shotpeening

Alternative to Shotpeening

Alternative to Shotpeening

(OP)
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?

RE: Alternative to Shotpeening

What size spring, and what is the spring material?

RE: Alternative to Shotpeening

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

RE: Alternative to Shotpeening

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.

RE: Alternative to Shotpeening

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.

RE: Alternative to Shotpeening

(OP)
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.
 

RE: Alternative to Shotpeening

"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.

RE: Alternative to Shotpeening

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

Thanks again

RE: Alternative to Shotpeening

You're welcome, good luck.

RE: Alternative to Shotpeening

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

RE: Alternative to Shotpeening

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

RE: Alternative to Shotpeening

(OP)
Thanks again for the info everyone

RE: Alternative to Shotpeening

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

RE: Alternative to Shotpeening

(OP)
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
 

RE: Alternative to Shotpeening

Why not just use preset?

RE: Alternative to Shotpeening

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

RE: Alternative to Shotpeening

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

RE: Alternative to Shotpeening

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.?

RE: Alternative to Shotpeening

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.

RE: Alternative to Shotpeening

Hi ckozka

If fatigue is a concern with your spring then the spring should have the last coil closed and ground square, if you leave the end plain and not closed then the load applied will be eccentric to some degree and result in a higher stress for a given load on that spring.
Israelkk's idea sounds very good to me using preset.

desertfox

RE: Alternative to Shotpeening

Is the spring deflects between the load points only? If this is the case the calculations indicate that it should withstand the 10M life cycle. However, is there a possibility of impact or very high load rates? If not I would check again surface conditions of the spring under X10 magnifications for surface defects.

Is the spring accepts electro chemical coating such as zinc? If it does check for hydrogen embrittlement correct removal process.

With regard to preset you need to calculate for maximum available cold working to get the most of the preset process.

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