Rolling cone shapes

M. Moore · Dec 30, 2018

I am quoting a job that requires quite a few flat topped cone shapes.
Rough sizing is 17" large diameter, 12" top diameter and about 28" tall and it will be 12 gauge aluminum.
I do have a nice Webb pinch roll that has been working well for the thicker steel plates.

My question is how to get a decent seam with no flat spot. I am getting pretty good at doing my steel plates and I can minimize the flat spots but with the conical shape and such thin material I need some sage advice.

Anyone have any tips on how this can be done?

I don't have the original cone rolling attachment for the Webb so I will have to make one. There would be more than 100 of these to do and I am also wondering if I should get the blanks laser cut or plasma?

Thanks,
Michael

Strostkovy · Dec 30, 2018

I've done it with a plate roller. It's easy enough on most of them to set one side to 12" and the other to 17", but you will be fighting it because the material wants to feed in straight but you need to feed it in an arc. I just worked it in three inch increments but it wasn't fast by any means.

What does this the best is a roller with cone rollers. If you have a lathe that can make suitable rollers that would be best, but that may not be practical.

Now that I have a press brake I use that for all of my plate forming needs but that's generally for personal projects.

If it helps in your research the truncated cone shape you are describing is called a frustum.

Bondo · Dec 30, 2018

There are 2 ways of doing it without it just coming out perfectly from the roller the first time.

1- roll your cone, barely weld it up and put it back through the roller.

2- roll your cone, weld it up completely then slide it on a pipe that is as big as you can and shape the weld seam. Or roll it, then beat it around a pipe, then weld and finish shaping it.

Rolling cones can be a big learning curve and it is always best to take the time to learn the machine.

Sent from my SM-G960U using Tapatalk

DDoug · Dec 30, 2018

With 100 pieces, can you sub it out to an expert vendor ?

gbent · Dec 30, 2018

Another way of getting perfect seams is cut your piece overly long. After rolling cut off your start/finish tabs. Works good on floppy stuff like 12 gauge and smaller.

M. Moore · Dec 30, 2018

Thanks for all the replies while I was sleeping.
Not sure that I want to beat on the seam area, these will be for furniture bases and need to look very good.
I will reasearch subbing them out but I do like a challenge and I have the equipment already.

I like the idea of leaving the material long but can’t think of a good way to make the cut? Also the material size just fits on a 4 x 8 sheet, bigger would mean lots more material and cost.

For my current shapes I just prebend after feeding through and then turn around and feed through and roll from back to front. This results in a near perfect shape if I guess correctly on the prebend.
I usually bring the back roller up a good percentage higher than the finish pass.
I am almost always using 3/8” steel for these jobs.

I also just restored a Brown Boggs 30” roller that does 12 gauge steel, it is not powered but it might give a better result than the big roller?

Strostkovy · Dec 30, 2018

A weird way I've done it as well was to take a 2" diameter piece of round bar and set it in a 2" gap in one of my welding tables. I blocked up one end slightly, then repeatedly dropped it on a piece of sheet metal place over the gap. The blocking on the pivot side set the angle of the cone. It was hokey but went way faster than the roller.

hobbyman · Dec 30, 2018

Maybe make sweeps to check large and small ends then prebend all the ends by feeding in a short distance from the back with the pinch rolls tight and the back roll tilted. If you have a good set of rolls then the flat spot will be minimal. Allow that the weld on the outside will will flatten the curve and inside will increase the curve. Adjust your prebend according to which side your weld will be. Plan to make at least 105. You will have some dead soldiers.
Keep in mind that aluminum is very problematic with grain direction. If your parts are just cut from the sheet at random then your bends will change between parts.
Not sure about choices on cutting. Years ago I talked to a guy who had a laser cutting table and he complained how reflective the sheets of aluminum were and how it shortened the life of his consumables. If you have plasma cut there is no doubt that you will have to prep the edges to remove oxide.

snowman · Dec 30, 2018

I would absolutely get those laser cut. Not plasma cut...laser edge is much nicer.

I've done a few jobs like what you suggest. Fortunately, the length of the hypotenuse was small and I could hand hammer it in (plus it was always stainless, so it reacted better to hammer faces).

An easy way of doing it is to leave an extra inch or two on each end so the cone overlaps. Then spring it out a little for kerf, clamp with vise grips, then do a final cut on a table saw, or a vertical band saw if you are so lucky. It springs back to leave a perfectly matched cone.

Ken hosford · Dec 30, 2018

I have seen a 2 wheel rolls were the lower roll was urethane and the upper was steel you set the bend by the deflection of the lower rolls surface. making near perfect ends . The upper wheel needs to be quick detachable . To roll cones in this manor the rolls need to be conical . the soft roller can be made as large as you want to deal with the load . I have seen belt sander pulley made out of stacked paper . you could cut discs of urethane and stack to achieve the result possibly alternating + then - in dia. to change hardness . A pretty crude cone roller could be made this way 3 1/2" pillow blocks 3" pipe for axles . the hard rller could be made same way with mdf discs then turned eve osb then epoxy

Illinoyance · Dec 30, 2018

Not done it but watched it done: Put the part in the rolls upside down. Just enough pressure on the top roll to hold the metal in place. Use a soft hammer to form a pre-bend against the bottom roll. Do the other end in a similar manner. Revers the plate and roll the cone in the conventional manner.

M. Moore · Dec 30, 2018

Good stuff guys.
I think I will talk to the local laser shop about cutting.

My Webb roller has a powered back roll so I don’t think it is very easy to angle it, I was under the impression that the pinch rolls were slightly angled to allow for the small end of the cone to slip a little as it rolled through. That is the reason for the cone roller guide attachment.

I like the idea of cutting on the tablesaw, these are 28” long and won’t fit any of my vertical bandsaws, lol.
The problem with that is the extra material, I can just squeeze the shape out of a 48 x 96 sheet, three pieces per sheet, with only a small amount of waste. No random cutting with this size.
I can use a 5 x 10 sheet , four pieces per, but there is more waste. I also have to check what is available from my supplier, these holidays are a pain for quoting.

It sounds like some folks reading my post don’t quite understand that these will be rolled from a 31” x 48” piece, if it was a rectangle.

I won’t be dropping a round bar on them to make the shape but thanks for the input.

I am just quoting the job, my guess is the frustrum shape will be too expensive but you never know.

EmGo · Dec 30, 2018

M. Moore said:
I am just quoting the job, my guess is the frustrum shape will be too expensive but you never know.

Shouldn't be ... in the heyday of two-strokes there were guys in LA that would make onesy-twosey cones any size you wanted (admittedly not as big as yours but same idea) and they were cheap.

Nice welds but probably not furniture-grade ...

Strostkovy · Dec 30, 2018

Just to clarify you will be having a section of a ring cut, not a rectangle, right?

If you send out the correct file you don't need any trimming of the top or bottom and it's easier to weld because you can force one edge against the table with a ring and it either becomes a near perfect cone or buckles.

M. Moore · Dec 30, 2018

Strostkovy,

Yes, it will be the proper shape, you missed the "if" in the above paragraph.

I am still researching the rolling part and also looking in to having them done.
The problem with bidding on jobs where you haven't actually done the process before is the hidden surprises, like, oops this is taking twice as long as I estimated for the rolling part. Hard to make up that time. When doing 2 it is not such a big deal but multiplying anything by 100 is a much bigger deal, it also may turn into 400.
I do have the machines to do the rolling so it would be fun to take on the challenge but I don't like surprises.

Michael

Search

Largest Manufacturing Technology Community on the Web

Search

Rolling cone shapes

M. Moore

Titanium

Strostkovy

Titanium

Bondo

Hot Rolled

DDoug

Diamond

gbent

Diamond

M. Moore

Titanium

Strostkovy

Titanium

hobbyman

Hot Rolled

snowman

Diamond

Ken hosford

Cast Iron

Illinoyance

Stainless

M. Moore

Titanium

EmGo

Diamond

Strostkovy

Titanium

M. Moore

Titanium

Similar threads