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sheet metal bending question

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  • metalmagpie
    replied
    Well, after I cut the sheet into 4 parts the rest was pretty straightforward. Thanks to all. Here's one last picture. In it the shape is just roughly clamped together, but you can see it's going to work. Sorry for all the raggedy protective wrap, it's going to come off next.

    metalmagpie

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  • metalmagpie
    replied
    Not trying to keep this going unnecessarily long, but I wanted to point out that NONE of these bends are 90 degrees.

    I am pretty good at shop math but calculating the bend angles has thus far escaped me. Each panel is 12" wide at its narrow end, 22" wide at its wide end, and 12" tall. Note that the base is 10" wider than the top, so the two triangles on each side are both 5-12-13 by random luck.

    metalmagpie

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  • J Tiers
    replied
    If your 3in1 has a solid bottom die you will have more trouble than you think......

    The original issue was seeing if it would be doable on a B & P bender. Answer is either "almost" or "maybe".

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  • CCWKen
    replied
    Geez, you guys are turning this into a career. I could bend that up on my 3n1 in a few minutes after a finger setup. I've made a number of battery boxes of similar design. The "pyramid shape" makes no difference. If the short side flanges were odd dimensions, It would take me a couple of more minutes to step the bend across. (My fingers are even inches.) I'd do the long side flanges by hand and last since they look opposed to the short side and would interfere with the V-die. Done. Spot weld it up and paint it!
    Last edited by CCWKen; 08-04-2016, 08:47 AM.

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  • BCRider
    replied
    When I was doing this stuff the common practice was to bend up the flanges first. But in this case the shape is causing a problem with that method. We can't bend even one flange without the bend extending onto the other "flat" areas that we do not want bent if we are using a finger brake. At least not unless we have a finger brake that has a clear jaw end so the majority of the plate can overhang the front bending leaf.

    The only way to do this shape on a finger brake is to bend the box joints first to shape the truncated pyramid shape. Then bend the flanges as far as we can before the box fouls up on the fingers. Then finish the flange bends by hand given that 'magpie has mentioned that he is using thin easily bent stock.

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  • boslab
    replied
    Just looking I'd guess a box and pan aka finger brake could do that, it may even be possible on a beam brake if the throat will open wide enough for a jumper plate the size of the flange to fit, the beam clamps the jumper, the jumper clamps the stock, I can do flanged bends on my old Edwards up to about 1".
    Your just treating the folder as a big bending bar, it's useful to get some blocks to allow flanges to be folded with the flange turned up, a square edge is all that's needed.
    I may be proved wrong trying but I'd guess it would work.
    Mark

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  • Ridgerunner
    replied
    I see what you mean. If I can get some time it would be interesting to see if something acceptable could be done.

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  • J Tiers
    replied
    The key difference with the original post is that it is tapered. That causes the blank to be somewhat circular, and brings the blank across the bend line of other bends. That is a complicating feature, which affects how much finessing is required.

    A straight-sided box, as in your pictures , is precisely what a B&P brake is designed to do easily, and is therefore trivial by comparison. The direction of bends can affect how easily the part is made, but the blank is not in general an issue for falling across the bend and interfering with the table.

    The OP's blank


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  • Ridgerunner
    replied
    If this is what is in the first drawing I did it real quick on a Tennsmith box and pan brake. Depending on the dimensions it is no problem. The Z was bent first. I did 90 degrees on the Z flanges since that might be harder. There was no attempt to cut the notches at a 45, just guessing. The ending flange can go on the inside. I put it on the outside for the picture.



    Last edited by Ridgerunner; 08-03-2016, 06:45 PM. Reason: added on the Z flanges for clarity

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  • strokersix
    replied
    I think deltap has it! This is how I would do it. With care and appropriate clamping and support you can do nice work with soft mallets. Don't just swing away at it. Gently form the flange a little bit at a time. If you get heavy handed you will stretch the flange and cause a curve in the part.

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  • deltap
    replied
    I would bend the small end flanges first. They are only about 45 degree bends. They can be done in a standard brake by using a mallet instead of the bending leaf. Position the bend line even with the front edge of bending leaf. Gently hammer the flange down to the approximate angle. Now bend the side corners in a B&P. Spring it open and remove from brake. Close the corner seam. Return to B&P and complete large end flange bend.

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  • Kiwi
    replied
    Assuming the photo shows the full size and it's not heavier than 18# steel it will fold up in a box pan just fine remember it will spring enough to get it into position to fold

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  • BCRider
    replied
    The bends can be done with a regular bending brake, since you have your choice of lengths of bottom and top die. Some home shop type brakes, like the common 3 in one (shear, bender and roller), have a single full width bottom die, and they don't allow that option, even though you can replace the top dies.
    Yep, that's what I figured too earlier. Such a brake would solve the issues to a "T".

    The way I have gotten away with stuff like that is to bend what you are calling the "pyramidal" bends (I called them "box bends"), and then "finesse" the box around the finger. With the box at least partly formed, the overlap bend can be out of the way.
    I've done my share of that too. And in this case it would likely work fine since Paul confirmed that it was being done in thin metal which could be creased at least on the brake then finished up with hand forming. If the flanges themselves had a nice open "V" at the corners the box joints could be bent up and the box closed and a good start on the flanges could be done up to the angle permitted. By that time the box would run into the fingers anyway. Then the bends can be finished up by hand forming.

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  • J Tiers
    replied
    It's not just the flange, it's the whole "half circle".

    It curves around and the extended bend line goes across metal for the 4 flanges on the "inner circle" of 4 flanges. The metal either needs to be elsewhere, i.e. already bent and out of the way, OR someplace has to be made for it to move without hitting part of the machine.

    A machine that allows a bend on the end, with material hanging off the table, is capable of making at least the outside two.

    In some cases, bending up the outside two panels will allow repeating the "outside the end" bend on the next two, which is what I would try to do. The actual piece is so big that may not work too well

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  • garyhlucas
    replied
    Some box and pan brakes allow you to drop the lower jaw and you can then insert a short block to clamp the metal and then there would be room for the flange to clear.

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