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      <title>Why use sheet metal features on flanges</title>
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      <div class="title_topic2" id="xps10_pagetitle">Why use sheet metal features on flanges</div>
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      <p class="para_topic">There are two reasons to use Sheet Metal features (<b class="uiTerm">Holes</b>, <b class="uiTerm">Slots</b>, <b class="uiTerm">Cutouts</b>, <b class="uiTerm">Beads</b>, <b class="uiTerm">Punch</b> and <b class="uiTerm">Solid Punch</b>) on flanges. The first is that these features can distort. The distortion occurs when you place one of these features on the distortion region of a flange. &nbsp;When the flange feature changes its state (goes from <b class="uiTerm">Unformed</b> to <b class="uiTerm">Formed</b>), the Sheet Metal feature will distort. &nbsp;A comparable Modeling feature will not distort and will fail to apply when the flange changes its state. The figures below show more detail of the distortion of a Sheet Metal feature.
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      <p align="center"><img align="bottom" src="graphics/distort1_new.gif"></p>
      <p align="center"><img align="bottom" src="graphics/distort2_new.gif"></p>
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            <p class="para_item">The second reason to use a Sheet Metal feature on a flange is when you want to place a feature on the web of a <b class="uiTerm">Flange</b> feature then RPO it across the bend face. When you do this the length of the bend face will change when the <b class="uiTerm">Flange</b> feature switches from the unformed state to the formed state. A Modeling feature placement control is the RPO, so when the <b class="uiTerm">Flange</b> feature changes its state the RPO maintains its dimensional values.&nbsp;A Sheet Metal feature does not maintain its placement RPO when the parent changes states. The placement RPO dimensions are only maintained when the parent is in its creation state. The figures below illustrate what happens to a Modeling feature versus a sheet metal feature when a <b class="uiTerm">Flange</b> feature changes from unformed to formed.
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      <p align="center"><img align="bottom" src="graphics/flange1_new.gif"></p>
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            <p class="para_item">The above figure shows what could be a Modeling <b class="uiTerm">Slot</b> or a <b class="uiTerm">Sheet Metal Slot</b> placed on the web of a <b class="uiTerm">Flange</b> feature. The Modeling<b class="uiTerm">Slot</b> or the <b class="uiTerm">Sheet Metal Slot</b> use the RPO from the marked edges to determine location,
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            <p class="para_item">The first figure below shows that the Modeling<b class="uiTerm">Slot</b> moved, because the RPO from the bend tangent line determined its new location when the <b class="uiTerm">Flange</b> feature changed from <b class="uiTerm">Formed</b> to <b class="uiTerm">Unformed</b>. 
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      <p align="center"><img align="bottom" src="graphics/new_model.gif"></p>
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            <p class="para_item">The figure above figure below shows that the <b class="uiTerm">Slot</b> did not move, because when the <b class="uiTerm">Flange</b> feature changed from <b class="uiTerm">Formed</b> to <b class="uiTerm">Unformed</b> the RPO did not determine the location of the slot.
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