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      <title>Neutral Factor and Bend Allowance Formula</title>
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      <div class="title_topic4" id="xps10_pagetitle">Neutral Factor and Bend Allowance Formula</div>
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      <p class="para_topic">Whenever a material is bent, the material compresses inside the bend region and stretches on the outside. The <b class="uiTerm">Neutral Factor</b> is based on a calculation of the neutral axis (the point in a bend where the tension of the outside of the bend and the compression of the inside become neutral). This value is always a percentage of the material thickness as measured from the inside radius of a bend region. 
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      <p class="para_topic">You could also say that the <b class="uiTerm">Neutral Factor</b> is the percentage through the material where the length of the surface in the flat state is equal to the arc length of the surface in the bent state.
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      <p class="para_topic">Since you usually design parts in NX Sheet Metal in the bent state, the <b class="uiTerm">Neutral Factor</b>&mdash;in conjunction with the bend allowance formula&mdash;is used to calculate the length of the bend region in the flat state. This happens, for example, when you use <b class="uiTerm"><a class="links" href="javascript:void(0)" onclick="top.openFile('nx_sheet_metal/unbend_over.html');return(false);">Unbend</a></b> or <b class="uiTerm"><a class="links" href="javascript:void(0)" onclick="top.openFile('nx_sheet_metal/flat_pattern_over.html');return(false);">Flat Pattern</a></b>.
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      <p class="para_topic">The <b class="uiTerm">Neutral Factor</b> in NX Sheet Metal is part of an internal bend allowance formula, as follows:
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      <p class="para_topic">Neutral Surface Length = rad(Angle) * (Radius + (Neutral Factor * Material Thickness))</p>
      <p class="para_topic">You can also use other bend allowance formulas in NX Sheet Metal. You can define your own formula in <b class="uiTerm">NX Sheet Metal Preferences</b> so that the bend region deformation is calculated using your formula rather than the default.
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