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eccentric cone

eccentric cone

eccentric cone

I am trying to find a supplier to manufacturer 2 identical eccentric cones. Material is SS316L and customer will allow one piece rolled/welded eccentric cone or machined. My problem is that I need 6.35mm wall thickness due to temp and creep rate. The small ID is 5.1" and large ID is 9.5". Piece is 12" long. I can not find anyone to machine this unless I go to EDM machining at 1000.00 an inch and I can not find a roller to go over 3/16" thickness with 5.1" diameter. Anyone have any suggestion. I should also add that I need to manufacturer in non-contamination enviroment. No carbon steel can contact stainless steel at any time including shipping. Looking for possible vendor for work that someone has used in past or alternative method of making cone.

RE: eccentric cone

If those were pipe sizes, Alaskan Copper could help you...but the closest size is a 10" x 5" (10.75 o.d. x 5.64 o.d.) eccentric reducer, and the length is 7" not 12. Still, you could call them and ask...


(click the link for "concentric and eccentric reducers")

RE: eccentric cone

The one-piece only requirement sounds negotiable if there is no way to make this part except for the edm. ($1000/inch in which direction?)

You might be able to hydroform it in one piece with no seams, that tooling wouldn't be too expensive. Probably depends on how eccentric. Trim the nose off after forming.

RE: eccentric cone

Note that rollers are rated for a thickness over their entire width, typically in mild steel.

It may be possible to form thicker material over a smaller width, as here, if you can find someone willing to force his tooling and risk damage.

Unfortunately, the requirement for stainless may make the problem more difficult because of work hardening.

If you started with annealed stainless, then rolled it as tightly as you dare with a particular tool, then beat the hell out of it over a sturdy mandrel, you might be able to close the cone enough to weld it.

Can you accept a part with hammer marks?

Mike Halloran
Pembroke Pines, FL, USA

RE: eccentric cone

Seems like a lathe could do a concentric reducer easily - even on a manual lathe.

A programmed CAD/CAM unit ought to be able to do an eccentric reducer by "demanding" a ID/OD offset at the eccentric reducer's angle by cutting each diameter, then going one index axially, then cutting each diameter again. Use an offset at the cutting distance: assume a 0.005 axial distance offset for example, then polishing it after it is off of the CAD/CAM to remove the machining grooves.

Seems like we need a "I NEED A" forum for people to ask for bids for odd-ball jobs and one-off productions.

RE: eccentric cone

The stainless "cleanliness" criteria for fabrication and shipping is straightforward, but you MUST be clear about what you require BEFORE the bid offer is made.

RE: eccentric cone

If you can stand the rippling effect you would get by the process, you could bump this to shape on a press brake.
You can use carbon steel tooling with stainless wrappers to protect the part. I would suggest bumping with a 1/8" advance.
But that would really be up to the shop doing the job. Since this is an oblique cone it will actually be oval in its true cross section, requiring several adjustments in the stroke of the press as the job progresses. Start at the outside and do the center last so that the part can close onto the tooling.

You are judged not by what you know, but by what you can do.

RE: eccentric cone

I was wondering how eccentric the oval would be - but not enough to bother modelling it. But, what if you lathe-turned a true cone, and then cut the ends on a bias...the ends would be oval, not round, but could perhaps be bumped/squeezed round to facilitate welding to the piping?

RE: eccentric cone

When Manufacturing oblique cones, a similar technique is often used, the cone is rolled on a roller leaving the ends oval. the finished piece is tack welded, then taken to a press where it is squeezed until the ends are round. The flanges are tacked on, then the whole part is welded.

You are judged not by what you know, but by what you can do.

RE: eccentric cone

Is this nuclear or military application? I'm curious as to why no carbon steel can contact the part during its manufacture. Would passivating or other chemical cleaning be acceptable? Is forming in 2 halves and welding an option? If this is a super-critical application, just spend the bucks to have it EDM'ed and be done with it. You'll never achieve those tolerances roll-forming, except by shear luck.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: eccentric cone

I am curious if the corrosion resistance properties of formed sheet vs edm'd from a billet are going to be different. It may be worth a little experiment to prove one way or the other.

RE: eccentric cone

rcmac21 (Industrial),
I would ask your customer the same question that ornerynorsk just asked, " Can you make the piece in two halves? "
You already have one weld joint, why not two?
Doing the part this way you can add sacrificial strips to the joint edges to facilitate forming, you trim these off prior to welding.
As I said Stainless or urethane strips on the tooling can keep carbon steel away from the part. But raw iron can be removed by grinding and polishing which you are going to have to do anyway.
I have no doubt that if your customer is picky he is going to do a ferroxyl test anyway, do yours first and remove any traces of free iron.

You are judged not by what you know, but by what you can do.

RE: eccentric cone

Electro-polishing will remove any surface contaminates from 316SS that are deposited during fabrication. This will allow you to use iron/steel containing tooling, making the fab job considerably easier.


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