6 Replies Latest reply on Dec 1, 2018 1:02 PM by Maha Nadarasa

    Hem on curved sheet

    Raj Chorghe

      Hi

      I need to give hem on curved sheet.

      Please find attached file and image.

       

       

       

      Thanks

       

      Raj

        • Re: Hem on curved sheet
          Rubén Rodolfo Balderrama

          Did you tried as Lofted Bend?

          • Re: Hem on curved sheet
            Kevin Chandler

            Hello,

             

            I'm not in front of SW today, so I can't see how you developed your curve.

            But my preferred workflow for creating curved sheet metal, such as for your part, is to start with a Thin-Revolve then convert this using Insert Bends.

            1. Satrt a sketch and draw a vertical construction line at the origin (length doesn't matter, this is the  revolve axis).
            2. Draw a solid vertical line with either its endpoint or midpoint vertical to the origin.
            3. Dimension the length of this second line to the width of the sheet metal part.
            4. Dimension the distance between the two lines to be the bend radius of the curved part.
            5. Save and exit the sketch
            6. Start the revolve command and it will default to a thin revolve (select thin revolve if prompted to close the contour).
            7. Set the thickness to your metal thickness (or something close to it, the thickness is later dictated by the Insert Bends)
              1. Select your thickness to be outward if the curve's radius was to the inside face, else set it to inward for an outside face radius.
            8. Select Blind and enter the revolve angle.
              1. Do not select Mid-plane as this defeats the conversion for the OP.
            9. If you require an arc length rather than a defined angle, then:
              1. Open Equations and create a global variable for your arc length.
              2. Using this gv and the bend radius dimension, use trig to compute the actual angle required to obtain the arc length.
            10. Select Insert Bends
            11. Set the bend radius to the curve radius.
            12. You now have a curved piece of sheet metal with valid end edges to create hems on.
            13. If you're not permitted to add hems on the curved part, unfold it, add hems arefold it.
              1. To unfold, select the edge that was the solid line from the revolve sketch.
                1. Even though the label for this entry states "face", you must select an edge.
                2. Of the four straight width edges, SW only lets you select the edge that was the line as I typed above. Invalid edges aren't accepted.

             

            This is the workflow I would attempt but it is untested, but I hope it helps.

             

            Kevin

             

            EDIT:

            I forgot to mention to watch your hem parameters if the hem is on the inner face as you may get intersection errors if the hem radius and length are such that the hem is within the arc portion.

             

            Also, I'm assuming this will be fabricated with the curve first, then the hemming.

            If so, the hem material will be curved as well and when bent, the hem portion will arc toward the inside face for an inner hem or arc away from the outer face for an outer hem.

            Either way, you may eliminate the curvature at the hems if you flatten the hems (effectively changing your continuous arc into an arc with tangential lines on each end).

            Thinking on this, you could alter your workflow to shorten the arc angle enough to add two tangent line hems.

            Then on your shorten curved metal, add a tab (just long enough for the hem) and a hem on one end and mirror them to the other end of the curve (about a mid-plane palne created from the thin revolve end faces).

            • Re: Hem on curved sheet
              Pardeep Yadav

              Draw the curve in one sketch to be used as a path and draw profile including hem in other sketch to be used as a profile. Now use swept flange tool from sheet metal toolbar.

               

              Note: profile should be connected with path.

              • Re: Hem on curved sheet
                Kevin Chandler

                Hello,

                 

                I tried my above steps and the revolve-thin edges don't convert into edges that a hem can use.

                Also tried adding a tangent tab but these didn't merge.

                 

                So I added an edge flange to each end.

                Also, to get the revolve angle, I used a chordal equation with the given data:

                This workflow isn't stable when changing the flange data, but it does flatten

                 

                 

                SW2018 attached.

                I hope this helps.

                 

                Kevin