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Thread: Tube Bending

  1. #1
    Associate Engineer
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    Jan 2013
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    Tube Bending

    First post - hopefully I'm in the right forum for this question.

    I'm designing a form die to put a 32.5 bend in a .75" steel tube with a .047" wall thickness.

    The design is currently set up with the upper punch being a solid block (pulley) with a 2.441" centerline radius.

    I am trying to find an accurate calculation for the amount of nitrogen (spring) pressure I will need to hold the tube in place as it is formed.

    Any help or direction to an online calculator is greatly appreciated. I haven't had much luck so far.

  2. #2
    Lead Engineer RWOLFEJR's Avatar
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    Mar 2011
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    Rochester Pennsylvania
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    Hi, and welcome to the forum...

    How many? How long? Any straight portion? When you say upper die I'm guessing there's also a lower die? What sort of circularity do you expect or require? I'm not seeing where you'd need any springs?

    There's more than one way to skin a cat. Lot depends on quantity, quality, finish dimensions and any further processing that the part might go through...?

    Right off I think if it's jsut a couple / few pieces or a hundred even... and you can stand some slight ripples just whip up a custom (for your radius requirement) conduit bender. If it's a few and you'd rather no ripples conduit bender and pack the tube with sand or flour etc. and cap it then trim after the bend. If there are a bunch of these then do a search "tubing bender" and either buy or build a bender with a mandrel and wiper block set-up. You're not going to need much oomph to move the part.

    More info and might be more help.

    good luck,
    Bob

  3. #3
    Associate Engineer
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    Jan 2013
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    I'm locked into the design as an in-press hand transfer die. No mandrel, no wiper. Qty is 15,000 per year. GDT profile is .4mm

    This is more of a form die than a tube bender, to be honest.....

    If you're familiar with tool and die work, the part will be placed on the lower stripper. The stripper compresses as the bend is put into the tube. As the tube bends, I expect it to slide a bit within the locators. The upper is a solid block capturing the tube within the stripper. The stripper needs nitrogen springs (cylinders) to maintain its grip on the tube as it is formed.

  4. #4
    Lead Engineer RWOLFEJR's Avatar
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    I see no reason for any springs or strippers for the part you described. (But then again I don't see the whole picture...) With the right dies that part can't go anywhere and with properly designed dies they won't stick. Is this a basic ram press? How long are these parts?

    I have a big epistle written up on how I'd do these with our equipment but then I questioned what you're running exactly & how long these are. In a nutshell... If they're short then a die set with multi-cavity upper and lower dies and bang as many at a time as you can within the limits of your press and budget.

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