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<a name = "hj-top"> </a><table class = "table1" id = "table11"><tr><td><table class = "DocHeader"><tr><td class = "DocHeader1" colspan = "2"><h1>About Tightness Restriction for the Resulting Structure</h1></td></tr><tr><td class = "DocHeader4" colspan = "2"/></tr><tr><td class = "DocHeader3"><table class = "DocHeaderIntro" id = "table12"><tr><td class = "Intro1Only"><p class = "shortdesc">The manufacturing constraints for tightness represent a possibility to prevent the
    remaining structure from having holes and breakouts in the defined restriction area. 
</p></td></tr></table></td><td class = "DocHeader2"><table class = "DocTopicsSeeAlso" id = "table13"><tr><td class = "TopicsTitle">See Also</td></tr><tr><td><a title = "You can define a tightness restriction to prevent the remaining structure from having holes and breakouts in the defined restriction area." href = "tso-t-user-TopOpt-DesArea-TighCon.htm#tso-t-user-TopOpt-DesArea-TighCon">Defining a Tightness Restriction in Tosca Structure.gui</a></td></tr><tr><td><a title = "This section gives information how undercuts in optimized models can be prevented using design variable constraints." href = "tso-c-user-TopOpt-DesArea-Undercut.htm#tso-c-user-TopOpt-DesArea-Undercut">About Prevention of Undercuts in the Model</a></td></tr></table></td></tr></table>
  

  
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    <p>The tightness restriction is a variant of the demold manufacturing constraint with
        the <code class = "ph codeph">MID_PLANE</code> parameter set to <code class = "ph codeph">AUTO_TIGHT</code>. The following
      figure shows an example with the default casting restriction (<code class = "ph codeph">MID_PLANE=AUTO</code>,
      left) in comparison to the tightness restriction (<code class = "ph codeph">MID_PLANE=AUTO_TIGHT</code>,
      right): </p>
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    <p>The elements are removed in a similar way to the <code class = "ph codeph">AUTO</code> option. This means
      that the elements are removed in the pull direction or in the opposite direction. However, at
      least one layer of elements will be present in the middle plane. The resulting "middle plane"
      is not necessarily planar. It might be a curved surface. </p>
    <p>The tightness is only checked within the restriction area. It is impossible to ensure a
      tight connection to elements outside the restriction group in the area of the boundary. </p>
    <p>The midplane thickness is controlled by the <code class = "ph codeph">RADIUS</code> parameter (midplane
      thickness = 2*<code class = "ph codeph">RADIUS</code>). The radius should be at least the size of the average
      element to ensure that a correct midplane can be found. </p>

    <table class = "Remark" id = "table132"><tr><td class = "Remark"><span class = "run-in.important">Important:
				</span><span class = "notecontent">
      <ul class = "ul">
        <li class = "li">For 2D models, the definition of a manufacturing constraint leads to a significant
          reduction of the possible solution space. If this option is used in combination with 2D
          models, an additional definition for the step width should be added using the
            <code class = "ph codeph">OPT_PARAM</code> command (the parameter <code class = "ph codeph">SPEED=SLOW</code> must be
          defined). </li>
        <li class = "li">Breakouts might occur if there are thin walls parallel to the pull direction. These
          areas should be excluded from the restriction group. </li>
        <li class = "li">For some cases (for example, for uniform hexahedral meshes with an aspect ratio higher or lower
          than 1) the default radius might be too small to determine a valid midplane. The result
          will contain holes. If this is the case, the radius must be set manually to a high enough
          value (greater than element edge length in the pull direction). </li>

      </ul>
    </span></td></tr></table>


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