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  #11  
Old 08-16-2019, 01:28 AM
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You might find that you have to make the cones in two pieces. The top of the bender where the punch is held will have a certain thickness. If you make the cones from one piece of material you'll find that as they start closing up they will run into the upper section and start pinching it. Getting the right amount of bend in a situation like this can be a bit tricky...
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  #12  
Old 08-16-2019, 04:13 AM
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Quote:
Originally Posted by LKeithR View Post
You might find that you have to make the cones in two pieces. The top of the bender where the punch is held will have a certain thickness. If you make the cones from one piece of material you'll find that as they start closing up they will run into the upper section and start pinching it. Getting the right amount of bend in a situation like this can be a bit tricky...


My thoughts to, especially with 1/8” material. Going to be a little stiff. 1/16” would be a little more flexible.


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  #13  
Old 08-16-2019, 07:31 AM
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Quote:
Originally Posted by MetalWolf View Post
Gerry, you don't have a slip roller?
I use my slip roller to make cones after I cut the pattern out.
No, I'm not a Platypus, so there are some tools I don't have.
Also this is a few thou off 1/8" thick.
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  #14  
Old 08-16-2019, 09:14 AM
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Quote:
Originally Posted by Ironman View Post
No, I'm not a Platypus, so there are some tools I don't have.
.......

Meh, having read a lot of Platys posts and seen your shop, I suspect there are tools and toys in your arsenal Platy doesn't have Gerry. I declare no contest on the comparison.

Platy does get extra credit for packing all his stuff into a garage and service van...... Poor bastard does not have the luxury of lots of space. It amazes me how he manages to get anything done.
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  #15  
Old 08-16-2019, 10:03 AM
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Are you going to lap the seam, or butt it?

Think of a box for simplicity. For a butt seam, 3 folds, the angle is 360/3+1=90.

For a lap seam, 4 folds, it is 360/4.
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  #16  
Old 08-16-2019, 10:10 AM
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Originally Posted by arizonian View Post
Another train of thought...



A template for both ends and one for the middle since your punch/die combo is not full length. For air bending, start with a depth of .135-.140 and then see how the template matches in the first four bends, adjust from there.Might want to cut a strip 1-1/2" wide and experiment.

What kind of press are you working with? 10/20/30 ton HF hydraulic press or a press brake with air bending dies?

On edit,...
18 * pi = 56.5487
56.5487/32 = 1.7671

For quickie calculating, I'm assuming 8" and 18" are the neutral axis. If your shooting for an outside of 8" and 18", the neutral axis is the OD minus one plate thickness. For an ID, add one plate thickness for the neutral axis.

And, yes, start from the ends and work toward the middle.
It's a press brake. I have another die with the same bottom depth and slightly narrower, might butt that up to get length and do some test pieces to see how that goes.
If all else fails I will split it in two pieces.
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  #17  
Old 08-16-2019, 10:29 AM
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If you are working with 10 ga, you could fabricobble your own dies. Some angle, flat bar, and round stock, and you could make up your own full length dies. I have posted images of my home made pressbrake before.

Unlike you, I am limited to 20 T and about 28" in length.
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  #18  
Old 08-16-2019, 04:18 PM
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Quote:
Originally Posted by Ironman View Post
It's a press brake. I have another die with the same bottom depth and slightly narrower, might butt that up to get length and do some test pieces to see how that goes.
If all else fails I will split it in two pieces.
Since you have a press brake, you're golden. Butting two dies together to get full length has been done forever, but they are usually the same profile. I take it the inside V is narrower, not just the outside. Can you rake the top punch frame to account for the slightly narrower section?

On edit, I left out some info in my first post. Changes are in italics.

1.5" die = .75 between bends on the small end

8*pi = 25.132
25.132/.75 = 33.5 bends

So call it 32 bends
360/32 = 11.25 degrees/bend

25.132/32 = .7854 between bends
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Last edited by arizonian; 08-16-2019 at 04:27 PM.
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  #19  
Old 08-16-2019, 08:52 PM
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All the cones we formed were 2 piece (formed in halves). Digger is right on the money with making a template. You can do a few bends and eyeball it with the template. To tight and a bunch of light shining under the template. Step on the bastard to open it up a little easily done with 10 gauge. Then back off on the bends going forward from that point, Our shop was mainly geared to making pipes, stacks, ductwork and transitions (square to round 1 duct to 2 etc) I don't know the layout math because I'm a mathematical "Tard" But, give me the parts and cut me loose on a press brake and I'll build you some cones transitions and whatnot. Our Pacific press was a Fuckin Monster 1250 ton and 20' between the side frames of the press plus a 2Ft. horn on the end for making cones and transitions. Press brake was one of my favorite machines in the fab shop unlike the angle rolls (AKA the Corkscrew Maker) God I despised that bastard.
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  #20  
Old 08-16-2019, 08:55 PM
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Today was a grand screwup.
After I had some trenches filled, I went to work on the cones. The arc angle was supposed to be 50.56 degrees. So I did that, ripped it out on the plasma, and started to bump it and quickly realized something was amiss. In my haste I did not notice the little minus sign on the screen. If the goddamn thing was correct it should have been -39.44 (90-39.44=50.56) Instead I set it at -50.56 degrees, which left a too narrow cone.
So now I will have to hurl out a half sheet of steel, or make a three piece cone. It's frickin amateur hour.

I decided not to track my time on the first one, and use the second one for a time model....good thing.
And a good thing I decided to split the cone before forming, and it now can have some joggling around and make better use of the plate.
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