Detailing Cone Cutout?
Detailing Cone Cutout?
(OP)
I am not sure if im in the right forum.
I have a cone drawn in 2d autocad and I am not sure how I determine how many degrees I make each bend if I have a random quantity of bends to make the cone come together seamless.
Any pointers would be great
Thanks
I have a cone drawn in 2d autocad and I am not sure how I determine how many degrees I make each bend if I have a random quantity of bends to make the cone come together seamless.
Any pointers would be great
Thanks





RE: Detailing Cone Cutout?
RE: Detailing Cone Cutout?
RE: Detailing Cone Cutout?
Are you making a fabrication drawing, or are you helping the sheet metal worker do the flat layout?
If you are doing the fabrication drawing, you should not worry about the flat layout. Specify the height, diameter, angle (or equivalent) and the tolerances. It is possible that the fabricators can roll it, rather then bend it in sections. You should call them and discuss this.
If you are helping the sheet metal worker do layouts, I would hope he knows how to do this, and that he can explain it to you.
One of the very first drafting jobs I had was to make a drawing of a sheet metal Y joint. The layout looked complicated to me, so I simplified it by making three straight, round tubes, with a flat interface plate. About a week later, the boss called me into his office, and showed me the fabricated part. The two upper Y tubes were tapered into the larger bottom tube, and there was no interface part.
Sheet metal workers are skilled. Do not insult their intelligence.
JHG
RE: Detailing Cone Cutout?
RE: Detailing Cone Cutout?
Now, if you really _do_ need to make a polygonal cone, you do it with a finite number of air bends in the brake, with the punch or the ram set down a little at one end, and the blank is a finite number of Isosceles trapezoids placed leg to leg.
Say there are 8 faces to the cone. The dimension of the smaller base of each trapezoid is 1/8 of the circumference of the cone's small end. The dimension of the larger base of each trapezoid is 1/8 of the circumference of the cone's large end. The legs of each trapezoid are equal to the slant length of the cone. As you increase the number of faces, the trapezoids get narrower, and in the limit the joined collection of trapezoids becomes a shape comprising two similar arcs joined by radial lines. If the arcs happen to be semicircles, i.e. the lines are colinear, the resulting cone will have an included angle of 60 degrees. But you knew that, right?
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
RE: Detailing Cone Cutout?
Thanks
RE: Detailing Cone Cutout?
The picture gets clearer.
It is too bad you are not on 3D CAD. I suspect this one would be fairly easy.
It can still be done in 2D. Draw your cone out as a set of 2D orthogonal views, with whatever number of sections you want. Hopefully, the top and bottom of your cone are both perpendicular to the axis, and all the sections are identical.
From a side view, pick an othognal face, and project it. This gives you an accurate length of the face. You can project the widths at the top and bottom from the top view. This is all old fashioned drafting board stuff that works fine in 2D CAD. An old drafting text will explain this far better than anything I can type in a note.
I take it you are going to punch out each face and weld them together?
You should think out fixturing carefully. You should be able to work out a gusset that will support each face at the correct angle for welding.
If your ends are not orthogonal and/or the overall form is not round, this method still works, but you will have to project each face. It will be a lot of work.
JHG
RE: Detailing Cone Cutout?
If so you know the top will all come from a point you know the length of the base Pi X D = 50.26”, you know the true length of one side the square root of 4.5 squared + 8 squared= 9.17.
So you want to draw a circle with a radius of 9.17 but you want the outside length to equal 50.26 which is an inclusive angle of 314.12 degrees. So the part you want would look like a round cheese with a portion cut out.
Like I said I might be misunderstanding what you want and these figures are only in my head so please check them (make a paper mock up) but I think that is what you want.
Hope this helps.
RE: Detailing Cone Cutout?
Thank
RE: Detailing Cone Cutout?
and 2 FEET in diameter at the bottom,
and 4.5 FEET deep, right?
I'm getting a blank of 228.167 inches OD and 28.674 inches ID, with an included angle of 302.681 degrees, for 1/4" thick mild steel.
If you divide that into 13 equal pieces, you can get two pieces out of a 4 foot by 10 foot sheet of metal, assuming butt joints.
My math is usually unreliable, so don't take my word for it.
To get the curvature right, i'd make a 3D model and use it to slice a couple of planes, or I'd make a scale model, and fit a couple of templates to the small and large ends of each segment, then scale them up and make plywood templates for use by the press brake operators.
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
RE: Detailing Cone Cutout?
RE: Detailing Cone Cutout?
It would take a pretty big slip roll, sure. Whether you can afford it depends on how many cones you have to make, and how nice they have to be.
The cone is shallow enough that for some purposes, you could just make it up as 13 or more flat segments, and not bother curving them at all, or maybe just crease them down the middle.
If you do need the pieces curved, and don't want to invest in a roll, you could make a wooden or concrete buck, and form them over that, with pneumatic hammers or by rolling your forklift over them, or something like that.
You didn't tell us the material or thickness. Relatively thin sheet would yield to a light- duty homemade roll.
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
RE: Detailing Cone Cutout?
Can anyone confirm that a rolled cone would have less stress consentration then a broke cone?
thanks
RE: Detailing Cone Cutout?
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
RE: Detailing Cone Cutout?
RE: Detailing Cone Cutout?
There will be a big difference in the amount of labor and time involved in forming.
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA