Tube Crimping

[MadMango]

Not sure where to post this.

I am looking for manufacturing advice for crimping a tube with an internal end cap. The OD cannot dimensionally change more than +/-.002, and forming the crimp must not move the internal end cap more than +/-.005.

Tube: .450"OD with .030" wall thickness, 17-4 steel
Crimp: ~.090" wide with .414"OD

I was told that roll crimping this feature may impart a twist on the OD of the tube, so I am looking to form this some other way. My concerns are that any method will deform the OD which is very critical. Internally we discussed that the tube could be crimped with a 2-part clamp about 50%, then rotated 90deg and then fully crimped to reduce deformation.

Looking for any advice or suggestions.

"Art without engineering is dreaming; Engineering without art is calculating."

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[mechengdude]

Are any other joining methods an option such as welding?

 

[MadMango]

Welding or brazing would have been easy, but due to some energetic (explosive) material housed in the tube at the crimp stage, it is prohibited.

The connection must hold ~19kpsi internal pressure, which as described above, does the job.

"Art without engineering is dreaming; Engineering without art is calculating."

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[CorBlimeyLimey]

Maybe speak to someone from;

http://www.h-htube.com/endforming.html

http://www.airmo.com/endforming/hand.htm

 

[Heckler]

we have used Rotary Swaging on products in the past.

Heckler
Sr. Mechanical Engineer
SWx 2007 SP 4.0 & Pro/E 2001
o
_`\(,_
(_)/ (_)

This post contains no political overtones or undertones for that matter and in no way represents the poster's political agenda.

 

[MadMango]

Heckler, was rotary swaging done on a tube of similar size as above? Do you recall having any torsional deformation?

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[unclesyd]

I would use the equipment from one of the companies posted by CoreBlimeyLimey to achieve the crimp you require without any torsional problems. We used equipment by Airmo
to form ends on thin wall tube and it worked exceptionally well.
We also uses the hydraulic expansion technology to expand a CS into an Al component.

 

[MikeHalloran]

Air cylinder manufacturers do it all the time.
Of course, they're using 316, not 17-4, and
the wall is thinner, and
the operating pressure is <250psi.

That's an ambitious design.



Mike Halloran
Pembroke Pines, FL, USA

 

[hydtools]

I've never used it. What about eletromagnetic forming?

Ted

 

[unclesyd]

hydtools' suggestion brought back memories form the recesses of my mind. We used this process in the late 70's to put a steel tube on an Al arbor. The only problems I recall was at the time we were pushing the capbilities of the machine and springback was a problem. The process was quite successful on other similar applications for components on high speed machinery.

http://www.magneform.com/apps.html

 

[MadMango]

Hydtools and Unclesyd, thanks for that. I'll have to research and see if their EMF is a concern for our energetics.

"Art without engineering is dreaming; Engineering without art is calculating."

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[MadMango]

Well, I contacted Magneform and they can't use their process on 17-4 steel. I'm waiting on a call from Airmo to see what they say.

If a commercial process isn't available, we are thinking about making our own tooling. We are leaning towards a 3-jawed chuck that can be hydraulically clamped around the OD to from the crimp. Can anyone offer any advice/experiences towards this method in regards to OD deformation? If roll forming is a viable option, what deformation concerns should I consider?

"Art without engineering is dreaming; Engineering without art is calculating."

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[hydtools]

PMF Industries has this website. They form stainless.

http://www.flowformingplus.com/?src=O

Ted

 

[GregLocock]

Check out the crimping machines used for hydraulic hoses. Some sort of collet chuck is the favoured approach, presumably because the synchronisation of the jaws is much easier.


I worked on one that was used to squash aluminium rings, there were no hiccups that I can remember, but it was a much more compliant system than yours. Since yours is not using the swage for sealing then a collet chuck (which leaves slight witness marks) will be fine.




Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[gt6racer2]

I would machine a shoulder into the tube ID ( with corresponding increase in plug OD ) to easily hold the 0,005" position, and then roll over the tube end to close it. This process will leave a nice rounded end and not expand the OD. Shock absorber manufacturers often use this process to assemble.

 

[dgowans]

MadMango,

Not sure whether this is suitable for your application, but you may want to check out:

http://www.avdel-global.com/avsealii.asp

 

[MadMango]

Dgowans, that's an interesting item, but I couldn't use that. There are bits of electronics that are housed in the "plug" of this assembly.

Gtracer2, we had considered this early on, but were worried about stress concentrations at the counterbored shoulder. This v-crimp almost triples the amount of material in shear.

"Art without engineering is dreaming; Engineering without art is calculating."

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[KENAT]

A former employer used swaging on cartridges.

Basically a shotgun shell (different filling) made of extruded aluminium with an aluminium end cap.

The cap was pushed in (up against an internal cardboard liner to make sure it didnt' go too far) and then the ends swaged.

It wasn't quite the same as your image though. The end was reduced in diameter slightly.

KENAT, probably the least qualified checker you'll ever meet...

 

[bvanhiel]

Can you machine the critical dims after you crimp?

-b

 

[Tmoose]

"Not sure whether this is suitable for your application, but you may want to check out:

http://www.avdel-global.com/avsealii.asp

"

Toward the bottom of the page it says
" Automotive low pressure applications "