Cone Forming

[metal30]

Has anyone had any experience forming large truncated cones(6 feet diameter x 2 foot diameter x 2 foot tall x 1/4" plate) with a press brake?

I have the flat pattern but I am having a little bit of trouble determining how to check that I am not over bending or under bending the break lines.

Would it be better to use a roll to make the cones?

Thanks for any suggestions

 

[plasgears]

Roll the cone if you can find or make the right back up rolls, otherwise you may end up with a spiral distortion.

 

[metal30]

So I guess the answer is that I really should be using a slip roll to roll the cones. And any distortions from trying to break them with the break press will have to be beat out with a hammer(this is what we have been doing). This is not really the answer I was hoping for, but thanks for the replies.

If anyone has any suggestions on anything that could be done to make the cones easier with the break let me know.

Thanks.

 

[MikeHalloran]

Since you only make one size of cones, you could make a punch and a die for the press brake that would form the blanks to the correct curvature.

By the time you buy the die steel, program a mill, form the p&d on a CNC mill, polish the working faces, try a few parts, recontour a bit, try again, polish and harden ...

It would be cheaper to just buy a brand new slip roll. They're not that expensive.



Mike Halloran
Pembroke Pines, FL, USA

 

[metal30]

Does anyone know a formula or good way to determine the angle between the breaks?

360 degrees divided by 40 scribe lines equals 9 degrees, but that is not the degree between the break lines.

9 degrees is the angle if you were breaking a cylinder.
Since the side of the cone is not parallel with the center line, the angle between the breaks changes slightly depending on the height of the cone.

On a 6 feet diameter x 2 foot diameter x 2 foot tall cone the angle between the breaks seems to be about 7 degrees.

 

[plasgears]

Years ago I procured a used 14 foot wing roller with capabililty to roll tapered wing leading edges. We used it to roll limo side panels on 10 foot stretches. The source was this huge used machine outfit near O'Hare.

 

[griffengm]

A company I used to work for made cyclones of various diameters using an apron brake. We generally made them in two sections and welded them together. Keep in mind that if you are dividing the circle of forty segments into two pieces, each half will have nineteen brakes, not twenty. A one piece cone would use 39 brakes for forty segments as the last brake would be on the edge.
There exist manuals for layouts of these types of forms from a sheet metal organization called "SNIPS", IIRC. They were not cheap but if you get into this type of thing even once a year they can be invaluable.
I tried chasing this down through Google and came up with this url:

http://store.bnpmedia.com/store/aec_online/hvac/index.html

There may be better.

Griffy

 

[DoctorColdSaw]

Hi,

I'm rolling much smaller cones (inches rather than feet).

Plasgears said "Roll the cone if you can find or make the right back up rolls, otherwise you may end up with a spiral distortion."

I have made a die set for my first cone because when I tried to make it on a slip roll I encountered the aforementioned "spiral distortion".

What are the "right back up rolls" in this circumstance? I imagined I'd need to use tapered rolls to truly roll a cone. Is it possible on normal straight rolls? Is there a special way to set them up for each cone or is it a learned skill thing?

I have some much longer cones to make and I'm buggered if I'm making a die set for each one if I don't have to.

Cheers,

Wilson.

 

[MikeHalloran]

I've never seen it done on anything but straight cylindrical rolls. The rolls were equipped with a simple looking stop that was apparently used to help the cone aligned.

The usual procedure involved preforming both ends to a modest curvature by beating them with a mallet over a cylindrical anvil. Then one precurved end was fed into the nip of the drive rolls, and the blank was driven almost to the other end. The rolls were adjusted for a little more curvature, then the blank was driven back. Forming proceeds the same way; tighten the curvature, drive the blank almost through, and reverse. There was a lot of beating on the curved edges to keep the cone aligned as the curvature was tightened up.

The blank is driven all the way through, making a couple of revolutions, after the straight edges touch.

My friend Francis made it look easy, but he does it every day, all day long, so there may be much more to it than meets my eye.



Mike Halloran
Pembroke Pines, FL, USA

 

[DoctorColdSaw]

Thanks Mike,

Its the sort of thing I think I'd like to see a video of your friend Francis doing. Its amazing what some folk can do if they've been doing it a while. Its even more amazing that you can sometimes pick up on what that is by just looking. Its how I learned to TIG aluminium.

Cheers,

Wilson.