rolling a precision sheet metal ring - How???
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  1. #1
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    Default rolling a precision sheet metal ring - How???

    Hey folks-

    we are a small (but important!) part of a prototype fab shop. My 'division' produces small perforated sheetmetal rings, mostly by hand. The size (# of pieces) of our orders are growing and we need to figure out how to accurately shape the rings, faster. Currently we use a hardened & polished mandrel (turned to a specific size, per the order) and small brass hammers. Yeah-- it is archaic, but with some practice we can get them within 0.040mm, or less. A typical part might be about 40MM Dia x 10MM wide x .6MM thick. We cut the perforated & formed strip to a precise length, form it sort of round in a sort of press, weld the ends together in a custom resistance welder, then precisely round them, as described above

    I have done large (3ft diameter) rings on one of those huge industrial rolling machines, but that was not precision work.

    Any suggestions on how to roll a ring like this, holding a +/- 0.150MM tolerance on the diameter?

    The boss is asking us to modify a small/cheap ring roller ($200 range), but it is looking like a goose chase.

    Anyone have an idea that works? Internet searches have led me to large hot-forged rings, but nothing as small & precise as we do.

    thanks for reading!

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    Roll, weld, and then expand to size.

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    To bend them Press them and press hard
    Use a piece of round as the upper die Press at the far ends only with a fork shaped piece
    Lower die is best less as 180Dgr
    This way the ends get bend too
    But I like the expanding idea to get them to size
    Your 0.04mm accuracy is that on the lenght of the diameter or out of round tolerance ?

    Is it possible to make these on a lathe with driven tool from solid ??

    Peter

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    Once you hit quantities, could this be a screw machine part? Probably pennies compared to your current approach.

    Failing that, I would do it the way you’re doing it now. Maybe the roll and weld could be rougher if you start oversized, expand on a mandrel for ID tolerance and finish, then turn the OD and edges?

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    Quote Originally Posted by Jeep-Power View Post
    Hey folks-

    we are a small (but important!) part of a prototype fab shop. My 'division' produces small perforated sheetmetal rings, mostly by hand. The size (# of pieces) of our orders are growing and we need to figure out how to accurately shape the rings, faster. Currently we use a hardened & polished mandrel (turned to a specific size, per the order) and small brass hammers. Yeah-- it is archaic, but with some practice we can get them within 0.040mm, or less. A typical part might be about 40MM Dia x 10MM wide x .6MM thick. We cut the perforated & formed strip to a precise length, form it sort of round in a sort of press, weld the ends together in a custom resistance welder, then precisely round them, as described above

    I have done large (3ft diameter) rings on one of those huge industrial rolling machines, but that was not precision work.

    Any suggestions on how to roll a ring like this, holding a +/- 0.150MM tolerance on the diameter?

    The boss is asking us to modify a small/cheap ring roller ($200 range), but it is looking like a goose chase.

    Anyone have an idea that works? Internet searches have led me to large hot-forged rings, but nothing as small & precise as we do.

    thanks for reading!
    Maybe have them spun?
    Metal Spinning & Water Jet Cutting – Syracuse, New York – Hy-Grade Metal Products Corp.

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    Pexto built a roller for doing production high tolerance rolling
    Very simple 2 roll bender Bottom roll urethane top roll under size to give room for over bend , lower roll powered slowly upper roll on quick release pivot so you feed stock into turning rolls when done you stop and release roll and remove ring relock roll and repeat
    All done with compressing urethane to give drive and bending very easy to built your own simple

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    Quote Originally Posted by digger doug View Post
    Roll, weld, and then expand to size.
    this is what we at doing now- as they are teardrop shape when coming out of the welder. THe trouble with the expanding part is that the walls of the formed edge get crushed & the perforations change size (they need to hold a specific tolerance, as well)

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    Quote Originally Posted by Ken hosford View Post
    Pexto built a roller for doing production high tolerance rolling
    Very simple 2 roll bender Bottom roll urethane top roll under size to give room for over bend , lower roll powered slowly upper roll on quick release pivot so you feed stock into turning rolls when done you stop and release roll and remove ring relock roll and repeat
    All done with compressing urethane to give drive and bending very easy to built your own simple

    this sounds promising-- any chance you have a photo of this setup?

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    Quote Originally Posted by Jeep-Power View Post
    this sounds promising-- any chance you have a photo of this setup?
    No pix needed.

    IIRC Diacro made a small one as well.

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    Just search online for 2 roll urethane slip roll. If the part needs straightened after welding you will still be doing so no matter what you use to initially roll the part though. I am not sure what is best in that regard, and I suspect the urethane rolls do not react great to difference in material. (bent welded joint will not bend the same as the flat material if you were to re-roll it after grinding the weld)

    If hammering by hand works, but you want to speed up the process. Maybe try making a set of dies that presses the welded seem back to the correct radius in one clamping action?

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    I made this semi-crude roller many moons ago and it worked well..made round parts day in and day out.

    Stuart

    smallroll1.jpg.jpgsmallroll2.jpg.jpgsmallroll3.jpg.jpg

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  14. #12
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    Quote Originally Posted by Jeep-Power View Post
    this is what we at doing now- as they are teardrop shape when coming out of the welder. THe trouble with the expanding part is that the walls of the formed edge get crushed & the perforations change size (they need to hold a specific tolerance, as well)
    Make the expanding mandrel grooved to match (and support) the formed edge.

    Have you tried a plasma or laser welder ? The hand held units like jewelry
    and lab people use.


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