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      <title>Output Pre-Drill points</title>
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      <div class="title_topic2" id="xps10_pagetitle">Output Pre-Drill points</div>
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      <div class="title_division">Pre-Drill</div>
      <p class="para_division">Pre-Drill creates and saves engage points in a temporary file so they can later be used in defining a Point-to-Point (drilling) operation. The Point-to-Point operation enables you to create pre-drilled holes which will allow the tool in a subsequent milling operation to engage along the specified tool axis (or Automatic specification) without removing material. This is necessary for milling tools which cannot plunge directly into material.</p>
      <p class="para_division">These points are defined by the processor based on the Automatic or Tool Axis engage moves. They are not defined manually using the Generic Point or Point Constructor dialogs. &nbsp;Processor defined pre-drill points automatically override any manually defined pre-drill points.</p>
      <p class="para_division">Engage points may be defined for single cut level operations or for multi cut level operations. For single cut level operations, you may generate engage points for all engages (points 1 &amp; 2 below), for the initial engage only (pt. 1), or for internal engages (pt. 2).</p>
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         <p align="center"><img align="bottom" src="graphics/pcmill_metfi10.gif"></p>
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      <div class="title_figure">Engage Points for a Single Level Operation</div>
      <p class="para_division">For multi cut level operations, you may generate engage points for all engages (points 1-9 below), for the initial engage only (pt. 1), for internal engages, (pts. 2-9), or for bottom cut regions only (pts. 8, 9).</p>
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         <p align="center"><img align="bottom" src="graphics/pcmill_metfi09.gif"></p>
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      <div class="title_figure">Engage Points for a Multi Level Operation</div>
      <p class="para_division">Creating points at every cut level sometimes results in an excessive number of pre-drill points. This, in turn, results in an excessive number of pre-drilled holes and added stress on the machine tool and cutter when the load on the tool changes as each of the holes is encountered during milling. The Bottom Regions option reduces the number of pre-drill points generated in multi cut level operations to a minimum.</p>
      <p class="para_division">When you generate the &nbsp;milling operation, the system retrieves the pre-drill points file. There is a flag stored in the file that indicates whether the point-to-point operation has already &nbsp;retrieved and accepted the current pre-drill points in the file. If they have, the pre-drill points are deleted at that time, before any new pre-drill points can be added.</p>
      <p class="para_division">When you save the point-to-point operation, the operation checks to see if there are points in the pre-drill file. If there are, a flag is stored in the pre-drill file which marks it for deletion the next time a milling operation accesses it. </p>
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            <td valign="top" align="left"><img align="left" src="../graphics/warning.gif" alt="Warning" title="Warning"></td>
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                  <p class="para_warning_body">The point-to-point operation does NOT delete the pre-drill points file when the operation is accepted and saved. It merely indicates that the pre-drill points file should be deleted the next time a milling operation attempts to append to it. </p>
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      <p class="para_division">The pre-drill points are saved in the database. The only time the pre-drill points file is deleted is when a point-to-point operation marks the file for deletion and a milling operation attempts to append points to the file during generation. Closing the part file does not automatically delete the pre-drill points file.</p>
      <p class="para_division">One advantage this behavior provides is in the situation where a large non-plunging cutter engages along the tool-axis. In such cases, your may need to use multiple drill sizes, hence multiple point-to-point operations, to create a hole big enough to land the cutter.</p>
      <p class="para_division">The Verify Predrill Points option allows you to list and redisplay the predrill points.</p>
      <p class="para_division">Refer to Predrill Points for more information on how the Point-to-Point module uses Pre-Drill points.</p>
      <div class="title_division">Interactive Sequence</div>
      <p class="para_division">To create Pre-Drill engage points, first specify the appropriate Engage Method. Initial must be set to either Automatic or Tool Axis, or Internal must be set to either Automatic or Tool Axis. At least one of the engage methods (Initial or Internal) must be set to Automatic or Tool Axis for the Pre-Drill options to be available.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/pcmill_metfi08.gif"></p>
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      <div class="title_figure">Engage Method</div>
      <p class="para_division">Second, specify All Regions or Bottom Regions as the Pre-Drill option. The availability of these options depends on the specified Engage Method.</p>
      <p class="para_division">Third, generate the tool path. This defines the Pre-Drill points. The points can be verified by selecting Options&quot;Verify Predrill Points.</p>
      <p class="para_division">Fourth, generate a Point-to-Point drilling operation using these Predrill Points.</p>
      <p class="para_division">Last, reorder the operations so that the Point-to-Point operation is executed before the milling operation that defined the Pre-Drill points. The milling operation now uses the pre-drilled holes when engaging.</p>
      <p class="para_division">The Pre-Drill options (None, All Regions, Bottom Regions) are described below.</p>
      <div class="title_division">None</div>
      <p class="para_division">None will not generate Pre-Drill engage points.</p>
      <div class="title_division">All Regions</div>
      <p class="para_division">All Regions can generate pre-drill points in every cut region of every level. Pre-drill points are generated for the Initial or Internal engages only when specified as Tool Axis.</p>
      <p class="para_division">When Tool Axis is specified for Initial (and only Initial), a pre-drill point is generated only by the initial engage (pt. 1 below).</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/pcmill_metfi07.gif"></p>
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      <div class="title_figure">All Regions, Initial</div>
      <p class="para_division">When Tool Axis is specified for Internal (and only Internal), pre-drill points are generated by all internal engages (pts. 1 and 1-8 below). A pre-drill point is generated for every cut region of every cut level except the initial engage.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/pcmill_metfi06.gif"></p>
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      <div class="title_figure">All Regions, Internal</div>
      <p class="para_division">When Tool Axis is specified for both Initial and Internal, pre-drill points are generated by the initial engage and all internal engages (pts. 1, 2 and 1-9 below). A pre-drill point is generated for every cut region of every cut level.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/pcmill_metfi05.gif"></p>
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      <div class="title_figure">All Regions, Initial and Internal</div>
      <div class="title_division">Bottom Regions</div>
      <p class="para_division">Bottom Regions generates pre-drill points only at the bottom cut level of each cut region (points 1 &amp; 2 below) to avoid creating an unnecessary number of holes.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/pcmill_metfi04.gif"></p>
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      <div class="title_figure">Bottom Regions</div>
      <p class="para_division">Bottom Regions is available only when one or both of the Engage Method options (Initial and Internal) are set to Automatic. Although the resulting pre-drill engage points will be identical regardless of the options specified for Initial and Internal, the tool path may differ. We recommend specifying Automatic for both Initial and Internal engages to insure that this milling operation can be successfully executed following the Point-to-Point drilling operation.</p>
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