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  1. #1
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    Default Bending sheet metal with a panbrake, bend lines

    I am trying to work out bending up a toolbox with a pan brake I am borrowing the use of.

    I did some test bends with some metal today and the machine seems to bend the material from where it clamps, which is how I would expect it works.

    It bends the metal with a 2mm radius on the inside bend. It is 1.6mm gal sheet.

    Fusion 360 gives me three lines in the sheet metal CAD. I assume it is the start of the radius, the centre, then the end.

    So with the panbrake do you mark out your sheet so you clamp it on the inside line of the bend.

    A pressbrake would you would mark out the sheet so the bending tool presses on the centre of the bend?

    Are there any incantations or special rituals to make it go easier. It makes mill work look elementary.
    Gold, the colour of choice for the discerning person.

  2. #2
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    I clamp on the line and bend. For thinish stuff that seems to work, for thicker stuff the bend is pushed out a bit. Because of that you want to work symmetrically - if you are being a U shape for example, clamp the base and bend, then (if you can) turn it around so you are still clamping on the base for the other bend. If you have multiple bends, start with the ones closest to the edge of the seam and work by pulling the sheet outwards.

    Good luck (lot of trial and error learning involved)

    Michael

  3. #3
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    When I'm folding toolboxes for example I work from the edges in, just make sure you don't get creeping. That's where you start with the sides at 150 high and the base 150 also, if you're not careful, you'll end up with 150 high on one side, 145 base and 155 on the other side. It's fun when you have something like 10 bends on an aluminium toolbox.
    Kryn
    To grow old is mandatory, growing up is optional.

  4. #4
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    Thanks, the box will be made in 4 pieces, it is 1100 X 300 X 275 high.

    The top will have a reverse bend so it has a lip standing up to stop water ingress. The ends will be bent separately with tabs folded in on pop rivet.

    I will bend the outer reverse edges first, then work from the base out. The panbrake is 2500 X 2mm capacity.
    Gold, the colour of choice for the discerning person.

  5. #5
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    Mar 2012
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    adelaide
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    Some thing to keep in mind is how the folder is set up as to what sort of folds you get , is the top clamp set back for material allowance or is that set on the clamping line and the front “ apron” lowered for material allowance

  6. #6
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    Fusion 360 is just guessing . I can't even remember how to calculate bend allowance, but that would just get you in the ball park anyway.
    In a perfect world 360 would get the fold allowance correct and the middle line would go on your hinge line. But that assumes many things, some of which you control, some you don't.
    If you're really after the best fit and need to hit your size, start with a strip say 50mm wide and 200mm long, put a fold line at 100mm, fold then measure the lengths of the sides. With your machine set up as it is, folding that width at that location, you have a "pretty good idea" of what your fold allowance needs to be and where the fold is in relation to the line. Though a longer fold will almost certainly change things, how much? that would be guessing. Make the adjustments you need to your part sizes and possibly fold a full length test piece? or just fold the body, measure, and adjust the end sizes to match. As MG said they tend to pull out, so you have to keep the direction in mind and your inside/outside sizes.

    But really, unless the toolbox needs to be +/- 0.1mm, if you work symmetrically(as I see you just posted). Then make the ends fit. you might end up a couple of mm short or long but at least the things that need to be the same will be.

  7. #7
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    So do I need to visit the local witch doctor first and have a sacrificial sacrifice to appease the bending gods before I start?

    I measured up the test bends, from the mark from the clamp to the other side of the bend averages about 3mm.
    Gold, the colour of choice for the discerning person.

  8. #8
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    Is the owner/operator of the machine able to give you the advice you need?

  9. #9
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    Nope, the machine is near brand new and the owner knows as much as I do about sheet metal bending.
    Gold, the colour of choice for the discerning person.

  10. #10
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    this is what I use...seems to work for sheet metal.
    bending.pdf

  11. #11
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    Quote Originally Posted by .RC. View Post
    So do I need to visit the local witch doctor first and have a sacrificial sacrifice to appease the bending gods before I start?
    Couldn't hurt.
    When you get down amongst it steel can have a "grain" that means it folds differently across the sheet than it does along the sheet. (though alum is far worse)

    Just how close do you want this toolbox to be? lol



    Omg someone that tells you to use K factor then tells you how to work it out! and that in effect it only works for that machine/setup. Give the man a gold star. The number of times I have seen K factor used as if the machine has no effect on it.

  12. #12
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    Well I do not want one side 10mm higher then the other. I have enough hand bent sheet metal stuff I have made that turned out like that already. I have already mastered that part of sheet metal work.

    Got to take your hat off to the sheet metal workers who manage to do it all right.
    Gold, the colour of choice for the discerning person.

  13. #13
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    Quote Originally Posted by tontonh View Post
    This post tells a story.
    Well I'm confused. Did you have a post in mind? or do you mean "thread"?

    Quote Originally Posted by tontonh View Post
    Don't you think you're making bending a piece of sheetmetal unnecessarily complex?
    Well now that depends, you tell me what the tolerance is and I'll let you know.

    Quote Originally Posted by tontonh View Post
    Why don't you just get a bit of scrap, bend it and work it out from there.
    Isnt that what most of the replies have said in one way or another?

  14. #14
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    Quote Originally Posted by tontonh View Post
    You certainly are confused,
    Yes I though I said that. Though your post hasn't helped, I'm still confused as to whether it is a particular post you have an issue with or the whole thread. No skin off my nose that you don't seem to know the difference.

    Quote Originally Posted by tontonh View Post
    Well, at the moment I'm tolerating your 'thread'.
    Oh I get it, a joke. Though I guess it would be funnier if it was in fact my thread.

    Now perhaps I could have added a smiley face to one of my previous posts or could have worded something differently, perhaps you weren't even talking about one of my posts, who knows. But until you know the tolerance you cant tell me how easy it's going to be. The fact that you think it's not going to the moon doesn't help much. Now granted its likely that as long as its symmetrical it will be "close enough" and its all good.


    Quote Originally Posted by tontonh View Post
    Incidentally, it's isn't not isnt
    I'm sorry that wasnt clear.

  15. #15
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    Could we please get back to the subject at hand and leave the personal stuff out of it!!!!!
    Have seen where this sort of thing has either seen someone banned, or severely reprimanded.
    Kryn
    To grow old is mandatory, growing up is optional.

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