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Pie-Cut Purge Exhaust for a Paint Robot

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  • Pie-Cut Purge Exhaust for a Paint Robot

    Paint robots require a purge switch connected to exhaust pipe to purge paint fumes from the robot so that the electric motors will not ignite the paint fumes. During the prototype phase to save time, we typically use the pie-cut method to construct the exhaust pipe. For the pie-cut method, we purchase mandrel bent elbows as shown in the first picture, cut them as required, then weld them together and weld on end flanges. For production, we will have a company mandrel bend the entire tube for us, with just the end flanges welded. The second and third pictures show a pie-cut and production purge exhaust pipe.

    For a prototype application, I needed to modify an existing exhaust pipe to change the geometry. First, I cut off the bends that were no longer required as shown in the fourth picture and then I chucked up the flange and turned off the weld from it. To get the 90-degree angle correct and the proper alignment of the bottom flange; I oriented the components on top of a print on my welding table and then tacked it in place as shown on picture 5.

    Pictures:
    1. Mandrel bent elbow
    2. Pie-Cut Exhaust Pipe
    3. Production Exhaust Pipe
    4. Cutting off bends
    5. Ready for tacking
    Click image for larger version  Name:	1. Mandrel bent elbow.jpg Views:	1 Size:	30.2 KB ID:	589750

    Click image for larger version  Name:	2. Pie-Cut Exhaust Pipe.jpg Views:	1 Size:	36.6 KB ID:	589751

    Click image for larger version  Name:	3. Production Exhaust Pipe.jpg Views:	1 Size:	41.1 KB ID:	589752

    Click image for larger version

Name:	4. Cutting off bends.jpg
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    Click image for larger version  Name:	5. Ready for tacking.jpg Views:	1 Size:	52.3 KB ID:	589754
    Last edited by Don52; 04-26-2018, 09:13 PM.
    Miller Thunderbolt
    Smith Oxyacetylene Torch
    Miller Dynasty 200DX
    Lincoln SP-250 MIG Welder
    Lincoln LE 31 MP
    Lincoln 210 MP
    Clausing/Coldchester 15" Lathe
    16" DuAll Saw
    15" Drill Press
    7" x 9" Swivel Head Horizontal Band Saw
    20 Ton Arbor Press
    Bridgeport

  • #2
    Picture 6 is a comparison of what I started with and what I ended with. Picture 7, 8 and 9 are some close ups of my welds.

    Pictures:
    1. Before and After
    2. Pipe Splice Weld
    3. Flange Weld 1
    4. Flange weld 2

    The pie cut method is commonly used, for making tight bends for race and performance cars, because they rarely have the time to mandrel bend up the entire tube.

    Click image for larger version

Name:	6. Before and After.jpg
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    Click image for larger version

Name:	7. Pipe Splice Weld.jpg
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    Click image for larger version

Name:	8. Flange Weld 1.jpg
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    Click image for larger version

Name:	9. Flange weld 2.jpg
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    Miller Thunderbolt
    Smith Oxyacetylene Torch
    Miller Dynasty 200DX
    Lincoln SP-250 MIG Welder
    Lincoln LE 31 MP
    Lincoln 210 MP
    Clausing/Coldchester 15" Lathe
    16" DuAll Saw
    15" Drill Press
    7" x 9" Swivel Head Horizontal Band Saw
    20 Ton Arbor Press
    Bridgeport

    Comment


    • #3
      Why do you have to have them mandrel bent after you made those pipes?

      Comment


      • #4
        Originally posted by ryanjones2150 View Post
        Why do you have to have them mandrel bent after you made those pipes?
        For the prototype exhaust pipes I welded together store bought elbows that were mandrel bent. The reason that they had to be mandrel bent is that the tubing had a very thin wall (1/16") and the bends were too sharp for a conventional bender. For the production exhaust pipes we sent the mandrel bending company our drawing and they sent us the bent up tube. We welded a flange on each end of the bent tube.
        Last edited by Don52; 04-26-2018, 06:16 PM.
        Miller Thunderbolt
        Smith Oxyacetylene Torch
        Miller Dynasty 200DX
        Lincoln SP-250 MIG Welder
        Lincoln LE 31 MP
        Lincoln 210 MP
        Clausing/Coldchester 15" Lathe
        16" DuAll Saw
        15" Drill Press
        7" x 9" Swivel Head Horizontal Band Saw
        20 Ton Arbor Press
        Bridgeport

        Comment


        • #5
          Originally posted by Don52 View Post

          For the prototype exhaust pipes I welded together store bought elbows that were mandrel bent. The reason that they had to be mandrel bent is that the tubing had a very thin wall (1/16") and the bends were too sharp for a conventional bender. For the production exhaust pipes we sent the mandrel bending company our drawing and they sent us the bent up tube. We welded a flange on each end of the bent tube.
          I'm thinking ryan meant, if you have fabricated a pipe that works, why have another made? Does the ID welds interfere with the exhaust flow?
          Last edited by Ltbadd; 04-28-2018, 01:41 PM.
          Richard

          Comment


          • #6
            That is precisely what I meant...thank you for clarifying it.

            Comment


            • #7
              Originally posted by ryanjones2150 View Post
              That is precisely what I meant...thank you for clarifying it.
              The pie cut prototype exhaust pipes are for our first prototype robot. The pie cut pipes are very expensive. The production exhaust pipes are for the hundreds of robots that we build after the prototypes.
              Last edited by Don52; 04-28-2018, 04:44 PM.
              Miller Thunderbolt
              Smith Oxyacetylene Torch
              Miller Dynasty 200DX
              Lincoln SP-250 MIG Welder
              Lincoln LE 31 MP
              Lincoln 210 MP
              Clausing/Coldchester 15" Lathe
              16" DuAll Saw
              15" Drill Press
              7" x 9" Swivel Head Horizontal Band Saw
              20 Ton Arbor Press
              Bridgeport

              Comment


              • #8
                Ah, that makes much more sense.

                Comment

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