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  1. #1
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    Default Aluminium microchannel tube serpentine bend

    Hi Guys,
    I'm new here and bit inexperienced in metal working. I've been trying to bend some aluminium microchannel tubes into a serpentine bend for a project of mine. I tried a hydraulic press and used some pipes placed at equal intervals to bend it as shown however I'm afraid that this might break/flatten the channels itself. Is there some standard/reliableIMG-20181213-WA0004.jpgIMG-20181213-WA0002.jpgIMG-20181213-WA0004.jpgIMG-20181213-WA0002.jpg way to do this?

  2. #2
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    If you can find some 'low melt' metal (Eutectic). Some of these melt in boiling water, and can be poured into the 'tubes'.
    When cool, it will help to maintain the profile of the extrusion when bending, then can be reheated to drain the 'low melt' out.

  3. #3
    BobL is offline Member: Blue and white apron brigade
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    Whatever you do it will really help if you anneal the Al before you bend it.

  4. #4
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    When bending soft metal tube/pipe, a lot of people pack the tube with dry fine sand or salt. This will help to minimise the tube from flattening when it is bent. The sand or salt can then be poured or washed out leaving the inside of the tube clear. I have no idea what the compressibility of something like paraffin wax is, but it is conceivable that you could fill the tubes with melted wax before trying to bend it similar to Brian's suggestion above.

    Simon

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    Back some 40 years ago I use to watch the guy`s bent thin walled pipe up to about 50 mm for furnace cooling systems.
    The pipes where filled with sand and capped at each end to stop the sand from moving around.
    They then used the biggest oxy/acyt heating tips I have ever seen then bend the pipes around the die by hand. Not a wrinkle or pinch to be seen.

    Probable falls into the lost arts group these days.

  6. #6
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    I've seen tubes filled with water and then frozen before forming ! I've also seen aluminium tube extruded into a former to make heat exchanger coils for dehumidifiers.
    Best Regards:
    Baron J.

  7. #7
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    It would help if we knew what sort of radius you're hoping to achieve. Is this going to be a one off, or a production run of these items? As others have already mentioned, filling the tube with dry sand or salt, then bending it around a former of the radii required. The former could be made from timber, to the height of the channel, then a follower with a bearing on the outside to roll it into shape.
    Something similar to this; https://www.google.com/search?q=DIY+...SmpkV2ANMkE8M:
    Hope this helps.
    Kryn
    To grow old is mandatory, growing up is optional.

  8. #8
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    Quote Originally Posted by KBs PensNmore View Post
    It would help if we knew what sort of radius you're hoping to achieve. Is this going to be a one off, or a production run of these items? As others have already mentioned, filling the tube with dry sand or salt, then bending it around a former of the radii required. The former could be made from timber, to the height of the channel, then a follower with a bearing on the outside to roll it into shape.
    Something similar to this; https://www.google.com/search?q=DIY+...SmpkV2ANMkE8M:
    Hope this helps.
    Kryn
    Hi Kryn,
    The radius I'm going for is pretty small, about 9.2 mm and there are no breaks, as in, these bends are in a continuous serpentine fashion. I did try the dry sand, but since the folds are too many and too small, some sand gets trapped and restricts the coolant flow.
    I did love Brian's suggestions. Hell, I didn't even know about wood's metal which melts at 70 deg C. Unfortunately, I couldnt source it in my country and importing it costs me about 600-700 $ a kg (and that is way more than what I had in mind). But that also kinda made me wonder if wax could do the trick. Has anyone tried wax for thin walled tube bending?
    Again, thanks for all the answers guys!
    Regards,
    Harshit.

    P.S. I will try the filling the tubes with wax and adding some stoppers to this makeshift die ive made and give it a go on monday. Will share an update!

  9. #9
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    Hi Simon,
    Yes, I was wondering the same. I'll try wax on monday. Perhaps the solder for soldering wires could also be used. It doesnt stick to aluminium and is pretty malleable. I've seen some people freeze water and do it too on youtube channels but idk. I'll give it a go if nothing else works. Thanks for the suggestion!

  10. #10
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    Quote Originally Posted by Briangoldcoast View Post
    If you can find some 'low melt' metal (Eutectic). Some of these melt in boiling water, and can be poured into the 'tubes'.
    When cool, it will help to maintain the profile of the extrusion when bending, then can be reheated to drain the 'low melt' out.
    That is awesome Brian. I looked into wood's metal and its amazing. unfortunately, I couldnt source it locally. I'll try Simon's suggestion and try wax. And if nothing works, I think solder might do the trick as well as it is kinda malleable. Thanks dude for the eutectic metal info!

  11. #11
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    Don't know what they do these days, but trumpets (the musical kind) were traditionally made by filling the annealed tube with water and freezing. Lots of bends in a trumpet.

  12. #12
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    pipebend2.jpgPipebend1.jpgpipebend3.jpg
    *UPDATE*
    So, I tried bending the pipe again by filling it with wax and it worked like a charm! The bends are uniform and there are no ridges popping up as compared to the previous attempt with minimal deformation.

    Next though, is figuring out the tonnage of the hydraulic press I'd need for such work. Does anyone have any idea about that?

  13. #13
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    How long? Will you form multiple bends simultaneously? I think any real press should do 10" or so but if you want to do 6 feet you'll need a beast

  14. #14
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    Hi Hashit, Guys,

    That looks like a good candidate for a "Step and repeat" operation ! A fly press would do that with ease. As would a pair of form rollers, that could even be made from hard wood, meshing like a pair of gears.
    Best Regards:
    Baron J.

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