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Tube End Forming - Rectangular to Circular

  1. Jul 24, 2016 #1

    I wish to manufacture a transition tube from 4"x1" rectangular section to 3" OD circular section. The height of the part is 3" and is supposed be around 2 mm (.082") thick. Currently I am planning to manufacture this in a hydraulic press using (custom made ) end forming tools. The forming will be done in 3 or 2 stages starting from rect. and gradually forming a circular section. Has anyone tried this before? Is there any alternative way to make this. I am looking to make 6 such parts. I have no idea of the spring back, so can anyone help me with that. Also can anyone suggest me some literature/ handbook to help me in the process,
    Material - Stainless Steel (304)

    Thanks in advance
    Last edited: Jul 24, 2016
  2. jcsd
  3. Jul 24, 2016 #2


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    Not really my field but perhaps it would be possible to make it from welded sheet metal? As you would a cone/funnel. Try making a paper template?

    Edit: Actually I think this would be difficult.
  4. Jul 24, 2016 #3


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    Or perhaps print one using a 3D printer and cast copies in aluminium?
  5. Jul 24, 2016 #4
    I forgot to mention material, its Stainless steel
  6. Jul 25, 2016 #5


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    If you try to do this by simple cold forming then :

    (a) the square tube will almost certainly split before the round shape is fully developed .

    (b) the round section will always retain a component of 'squareness' that you will not be able to get rid of .

    There are forming processes that would work but these would require sophisticated engineering facilities .

    @CWatters has the right idea . Make the transition piece as a welded fabrication . This type of work is routinely done in ordinary sheet metal fabrication shops .

    Working out the shapes of the individual parts for the fabrication is not particularly difficult .
    Last edited: Jul 25, 2016
  7. Jul 25, 2016 #6


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    For sure. Solidworks flatten feature makes turning most 3d surfaces into 2d shapes for profile cutting easy. The press brake operator does the hard part.
  8. Jul 25, 2016 #7
    Thank you
  9. Jul 25, 2016 #8


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    As explained earlier, any attempt to open the right angle corners to a 1.5” radius by bending will fracture the material.

    If you start with a rectangular section then, to prevent the fractures, you will need to cut along the tube corners prior to forming the circular section. After forming you will need to weld up the previous cuts with the new surface curvature and alignment.
  10. Jul 26, 2016 #9
    What is the pressure and use of the part you need. A piece like this is a moderately easy standard layout from the sheet metal world. It would be easy to layout a pattern copy six times and fold them up. A little skill on a TiG welder could even make water or air tight parts.
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