Making tube with changing diameter along the length 10

[sftvbr]

I have to make a tube with a variating diamtere from 45 to 60 mm. the thickness is 1mm. the length is 40 mm also and the diameter change happens like a 90 degree step in the middle of the length. The material is stainless steel

As far as I searched , there are two manufacturing methods, one is reducing the diameter from 60 to 45 mm (like tapering ) . the other is increasing the diameter from 45 to 60. My guess is the second one breaks and won't resist the deformation.

what suggestions do you have for evaluation and choosing between the methods ?

 

[BrianPetersen]

Overspecifying the requirements for a part makes it expensive, and it might make it impossible. Underspecifying your actual requirements means we can't answer the question for you.

"Stainless steel" is a vague description. There are countless types. Some can be formed readily, some cannot.
How accurate do the specified dimensions need to be
How accurate do UNspecified dimensions need to be (e.g. how much variation in thickness can you accept)
Does the step in the middle need to have sharp corners
How good does the surface finish need to be (A) along the diameters (B) at the corners (C) in the diameter-step
Does the step in the middle need to be "flat" (90 degrees as shown in diagram above) or can it be a conical transition from one diameter to the next and if so, over how much length?

Go back to the end use functional requirements for the part and establish how much wiggle room you have for altering the design slightly in the interest of making it easier to manufacture. Do you REALLY need an abrupt diameter step with sharp corners? Does the end-use function demand that? Understand that this geometry will be costing you money.

If you have to make one and you need that step transition, machine it from billet and get on with life.
If you have to make one and you can have a tapered transition with rounded corners and the surface need not have absolute uniformity, go to an exhaust system shop and get them to make you one from exhaust system pipe, and get on with life.
If you have to make lots of them and you cannot wiggle on the thickness, sharpness of corners, the step has to be 90 degrees etc., there is still something to be said for making this thing out of 2 pieces of tube and a washer, welded together. An automated fixture could weld this thing in a hurry.

 

[sftvbr]

Thank you all again for your attention and responses , I wish I had all these clarifications before :

- yes the part absolutely has fillets as Greg pointed out. like around 2 or 3 mm radii

- since the strain is 37% , then definitely the most deformable types of stainless steel ought to be used.

- the precision is not super high. therefore around 0.5mm tolerance should be acceptable

- the 90° is required, it can not be conical

 

[EdStainless]

I see only two straightforward options:
1. Buy hollow bar or solid billet and machine it.
2. Fabricate it from 3 pieces, two tubes and a plate. Weld and final anneal.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[handleman]

Oh yeah, Ed? What the heck would you know about tubing anyway?

 

[hendersdc]

The part may be able to be hydroformed starting with a smaller tube but you would probably need to give a little on the 90 degrees. They may need a degree or two to in the tool.

 

[BrianPetersen]

The requirement for the 90 degree step-change in diameter is the killer specification here. I'm with EdStainless at this point: machine from solid, or weld together from 3 pieces.

 

[Tmoose]

26 posts after OP. 21 posts after OP that are not OP's replies.
The 22nd post, which was by OP, should have been his first because it had some significant content to further his cause.
I tried to give OP a star for that informative post because it (finally) was informative, but it (the star) did not seem to stick.

 

[dvd]

https://www.nationaldieco.com/deep-drawn-parts/

 

[sftvbr]

Tmoost

Thank you very much, I just tried to edit my question but it sounds that it's a little bit late now. Thank you all for all the great hints indeed !

also, yet many of the first 22 posts, had great points in them, and I appreciate them as well

 

[ProEpro]

Something like this maybe?

https://www.cardinaluhp.com/fittings/concentric-reducer31ww

 

[SnTMan]

Still no clear info about quantity required.

...well in industrial scale...

Implies large quantity?

Regards,

Mike


The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[sftvbr]

Yes, but not in hundreds of thousand. the order is a bit lower, like a few thousand

 

[MikeHalloran]

At my first real job, we made step-tapered mild steel tubes to serve as the outer ends of a car axle housing.
Basically, a straight piece of 3.25" od X .25" WT tubing maybe 30" long was squeezed axially by a pair of carbide-lined dies in a hydraulic press.
... during which process the tubes' overall length grew by >.25".
One end was shrunk by ~.25" dia to fit into a bored hole in the center section casting.
The other end was shrunk in two steps, quite a long length to the spring seat diameter, and the tip to axle tube diameter over the roller bearing.
Then the l/r halves had all the brackets welded on, were torque tested by deadweights, both ends were chamfered, and the bearing bores bored and reamed.
Finally, the finished axles tubes were pressed into the center section and plug welded.
At a rate of something like 5,000 car sets a day.

My job for a while was carrying the shrink dies back and forth to the carbide grinder, who eventually arrived at the proper blend radii to allow the dies to last for months at a time, vs. a few hundred parts.

The tooling was fairly expensive, so for a few thousand parts, machining from billet makes more sense.



Mike Halloran
Pembroke Pines, FL, USA

 

[GregLocock]

Ah, there's a similar process known as sizing rubber bushings. Basically the outer metal tube is squished down in diameter to place the rubber in compression. The preferred way to do that is with a cylindrical bush, just push it down a taper. But we often need a flange on the outer, so instead they crush it radially with a hydraulic collet. That needs very little unique tooling.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[sftvbr]

Dear Mike : Thank you so much for your great answer !

dear Greg : I could not find a good link to view the operation, despite you gave a great explanation , could you please share some useful links ?

 

[GregLocock]

Sorry, no, I've only seen it done, never read about it.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?