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      <title>Helical</title>
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      <div class="title_topic4" id="xps10_pagetitle">Helical</div>
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               <p class="para_td"><a class="links" href="javascript:void(0)" onclick="top.openFile('mfgmilling/noncut_moves_ov.html');return(false);">Overview</a></p>
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               <p class="para_td"><a class="links" href="javascript:void(0)" onclick="top.openFile('mfgmilling/ncm_list_opt.html');return(false);">Options</a></p>
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               <p class="para_td"><a class="links" href="javascript:void(0)" onclick="top.openFile('mfgmilling/ncm_list_rt.html');return(false);">Related Topics</a></p>
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      </table><br><p class="para_topic"><b class="uiTerm">Helical</b> creates a collision-free helix shaped engage move that is tangent to the first cutting motion.
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            <p class="para_item">If a tangent engage would collide with the part, <b class="uiTerm">Helical</b> moves away from the part and produces a helix around the region start point.
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            <p class="para_item">If a helix around the region start point would collide with the part, <b class="uiTerm">Helical</b> ramps along the inner pass the same as <b class="uiTerm">Ramp On Shape</b>.
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      <p class="para_topic">Examples of <b class="uiTerm">Helical</b> engages created a safe distance from walls:
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      <p class="para_topic"><img align="bottom" src="graphics/ncm_safe_helical_ex1.gif" border="0"></p>
      <p class="para_topic"><img align="bottom" src="graphics/ncm_safe_helical_ex2.gif" border="0"></p>
      <p class="para_topic">The general rule for helical engage is that if the processor cannot find, based on the input data, an open area outside of material to engage the part, the tool will ramp to the cut level. In many cases when using Profile, there is room for the cutter to engage the part and remain outside of the material. In these cases the cutter will not ramp to the cut level. When cutting a cavity region where the number of passes and the horizontal clearance is set such that there is no open area for the tool to engage, the tool will ramp to the cut level. Otherwise, the tool will engage in the open area.</p>
      <p class="para_topic">&nbsp;If a helical engage cannot be executed or if you have specified Zig, Zig-Zag, or Zig with Contour, the system follows traces along the tool path as it ramps the tool into the part. The system follows a tool path that is away from the part walls to avoid moving the tool along the walls. After the tool descends to the cutting level it steps over to the first cutting path (if necessary) and starts the first cut as illustrated below.</p>
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      <div class="title_figure">Helical with Zig-Zag Tool Path</div>
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                  <p class="para_td"><b class="uiTerm">Helical</b> options
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                  <p class="para_td"></p>
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                  <p class="para_td"><b class="uiTerm">Diameter</b></p>
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                  <p class="para_td">The default diameter of the helix is 90% of the tool diameter to allow a 10% overlap of the tool. This prevents a post from remaining in the middle of the helix.</p>
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                     <p align="center"><img align="bottom" src="graphics/max.gif"></p>
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                  <div class="title_figure">Figure. Diameter (1)</div>
                  <p class="para_td">If the region is not large enough for the specified helix, the software reduces the <b class="uiTerm">Diameter</b> value and attempts the helical engage again. This continues until either the engage is successful or the path diameter becomes less than the <b class="uiTerm">Minimum Ramp Length</b> value.
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                  <p class="para_td"><b class="uiTerm">Ramp Angle</b></p>
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                  <p class="para_td">Controls the incline at which the tool cuts into the material, and is measured in a plane perpendicular to the part surface. The angle must be greater than 0 degrees but less than 90 degrees. The tool starts the ramping move where the specified <b class="uiTerm">Ramp Angle</b> and <b class="uiTerm">Minimum Clearance</b> geometry intersect. No ramping occurs if the area to cut is smaller than the radius of the tool.
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                  <div class="title_figure">Ramp Angle (A) with Minimum Clearance (B)</div>
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                  <p class="para_td"><b class="uiTerm">Height </b></p>
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                  <p class="para_td">Specifies how far above the cutting level to start the engage.</p>
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                  <p class="para_td"><b class="uiTerm">Minimum Clearance</b></p>
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                  <p class="para_td">Specifies the distance the cutter stays away from part areas that are not meant to be machined. Also specifies how far a backup retract ramps away from the part.</p>
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                  <p class="para_td"><b class="uiTerm">Trim</b></p>
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                  <p class="para_td">Cuts off the engage move portion that extends past the specified <b class="uiTerm">Minimum Clearance</b> value. Overrides <b class="uiTerm">Arc Angle</b> and <b class="uiTerm">Length</b> values.
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                  <p class="para_td"><a class="links" href="javascript:void(0)" onclick="top.openFile('mfgmilling/engret_auto_min.html');return(false);"><b class="uiTerm">Minimum Ramp Length</b></a></p>
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                  <p class="para_td">Specifies the overall length the cutter travels while making the engage move.</p>
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            <td valign="top" align="left"><img align="left" src="../graphics/note.gif" alt="Note" title="Note"></td>
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                  <p class="para_note_body">The <b class="uiTerm">Follow Periphery</b> cut pattern with <b class="uiTerm">Outward</b> progression traces the inner most pass of the tool path as it ramps into the part. If the inner most tool path is too constricted, the software traces along the next largest pass of the tool path. 
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