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      <title>Return Flange/Double break</title>
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      <div class="title_topic4" id="xps10_pagetitle">Return Flange/Double break</div>
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      <div class="title_division">Definition</div>
      <p class="para_division">A double break return flange is a return flange condition on the second bend radius. The picture below labels the basic portions of the double break return flange.</p>
      <p align="center"><img align="bottom" src="graphics/dfm_double_break_desc.gif"></p>
      <div class="title_division">Purpose</div>
      <p class="para_division">The purpose of this check is to ensure that enough clearance exists so that the double break return flange can be manufactured.</p>
      <div class="title_division">To Pass Check</div>
      <ul>
         <li>
            <p class="para_item">Opening distance (D) must be greater than Length Ratio value(?) x L</p>
         </li>
         <li>
            <p class="para_item">Height (H) must be greater than Minimum Flange Height value(?)</p>
         </li>
         <li>
            <p class="para_item">Wall angle (A) must be greater than Minimum Inner Wall Angle for inner panels, and greater than Minimum Outer Wall Angle value(?) for outer panels. (Note, the DFM Advisor dialog has a menu option where the panel type is specified.)</p>
         </li>
      </ul>
      <div class="title_division">Computational Method</div>
      <p class="para_division">For this DFM criteria, 2 types of section cuts are needed.</p>
      <ol type="1" start="1">
         <li>
            <p class="para_item">A section that is 3D-Radial (normal) to the flange tangency curve. This section will be used to determine the non-angle measurements (flange opening distance (D), the flange height (H), and the return length (L).)</p>
         </li>
         <li>
            <p class="para_item">A section that is normal to the flange tangency curve in the press view. This section will be used to compute the flange wall angle (A).</p>
         </li>
      </ol>
      <p class="para_division">These sections are shown below.</p>
      <p align="center"><img align="bottom" src="graphics/dfm_double_break_2sections.gif"></p>
      <div class="title_division">System Generated Sections, and theoretical lines</div>
      <p class="para_division">Remember, the DFM advisor uses the convention that thickness is opposite of the face normal from the sheet. If the sheet was not extracted from a solid, the sheet normals might be pointing in the wrong direction.</p>
      <p class="para_division">First, a 3d radial section (true view section) is cut on the faces representing the double break flange. Then, from this section the theoretical lines are created. If these lines represent the outside of the double break flange, they are offset by metal thickness to obtain the inside theoretical lines. The picture below illustrates this step.</p>
      <p align="center"><img align="bottom" src="graphics/dfm_double_break_theoretical.gif"></p>
      <div class="title_division">Measuring D, L &amp; H</div>
      <p class="para_division">Next a coordinate system is constructed where the press direction vector is projected into the same plane as our theoretical curves. This forms the +Y of our local coordinate system. D, L, &amp; H are measured from the inside theoretical lines of the double break flange. The measurements of H and D are parallel to this +Y, and the measurement L is perpendicular to the +Y axis. The picture below illustrates this.</p>
      <p align="center"><img align="bottom" src="graphics/dfm_double_break_meas.gif"></p>
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            <td valign="top" align="left"><img align="left" src="../graphics/note.gif" alt="Note" title="Note"></td>
            <td valign="bottom" align="left" width="100%">
               <div class="para_note">
                  <p class="para_note_body">  The opening distance (D) is from the end of the return length, to the inside theoretical curve (See picture with section curves and theoretical lines) from the part.</p>
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            </td>
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      <div class="title_division">Measuring A</div>
      <p class="para_division">The measurement of the wall angle (A) will be performed with the actual press direction vector. This vector is not projected into any plane to measure the flange wall angle. Therefore an additional section is cut that is perpendicular to the press direction. This section is represented by the black curves on the orange colored double break flange about. The section used for measuring wall angle A is labeled.</p>
      <p class="para_division">The side view of this section is shown below, and the wall angle labeled.</p>
      <p class="para_division"> <img align="bottom" src="graphics/dfm_double_break_angle.gif" border="0">    
      </p>
      <div class="title_division">Cost Penalty</div>
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            <col span="1" width="113*">
            <col span="1" width="113*">
            <col span="1" width="72*">
            <col span="1" width="98*">
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            <th bgcolor="#c0c0c0" colspan="1" rowspan="1" valign="middle">
               <p class="para_th">Deviation</p>
            </th>
            <th bgcolor="#c0c0c0" colspan="1" rowspan="1" valign="middle">
               <p class="para_th">Complexity Result</p>
            </th>
            <th bgcolor="#c0c0c0" colspan="1" rowspan="1" valign="middle">
               <p class="para_th">Added Cost</p>
            </th>
            <th bgcolor="#c0c0c0" colspan="1" rowspan="1" valign="middle">
               <p class="para_th">Complexity Value</p>
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            <td bgcolor="#f4f4f4" colspan="1" rowspan="1" valign="middle">
               <p class="para_td">L or D fail</p>
            </td>
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1" valign="middle">
               <ul>
                  <li>
                     <p class="para_item">...</p>
                  </li>
               </ul>
            </td>
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1" valign="middle">
               <p class="para_td">$XXX</p>
            </td>
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1" valign="middle">
               <p class="para_td">X</p>
            </td>
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               <p class="para_td">Wall angle (A) fails</p>
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               <ul>
                  <li>
                     <p class="para_item">...</p>
                  </li>
               </ul>
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            <td bgcolor="#f4f4f4" colspan="1" rowspan="1" valign="middle">
               <p class="para_td">$XXX</p>
            </td>
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1" valign="middle">
               <p class="para_td">X</p>
            </td>
         </tr>
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