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      <title>Avoidance &ndash; Drill and HoleMaking</title>
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      <div class="title_topic3" id="xps10_pagetitle">Avoidance &ndash; Drill and HoleMaking</div>
      <hr noshade="true">
      <p class="para_topic">Avoidance allows you to specify, activate, cancel and manipulate points, lines or symbols. These points, lines or symbols help you define tool clearance motion before and after an operation. This option also enables you to save the avoidance control parameters you have defined, which can then be retrieved for future operations.</p>
      <div class="title_division">Common Avoidance Sub-Options</div>
      <p class="para_division">After you choose one of the Avoidance Geometry options, the system prompts you to choose one of the following Avoidance sub-options:</p>
      <table border="0">
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            <td valign="top" align="left"><img align="left" src="../graphics/note.gif" alt="Note" title="Note"></td>
            <td valign="bottom" align="left" width="100%">
               <div class="para_note">
                  <p class="para_note_body"> NOTE: Some of the Avoidance options have one or two additional selections. Those selections are described below under that particular Avoidance option.</p>
               </div>
            </td>
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      </table>
      <p class="para_division">Specify allows you to choose a method of defining the point. The Avoidance Geometry symbol appears on the display screen at the specified location and remains displayed until the screen is refreshed. After you use Specify, the system shows the status as ACTIVE.</p>
      <p class="para_division">Omit allows you to disable tool motion to and from the Avoidance Geometry until you enable it again using the Reinstate option. The system shows the status as INACTIVE. If you choose Omit before you specify an Avoidance Geometry option, the system displays an error message.</p>
      <p class="para_division">Reinstate allows you to reactivate an omitted Avoidance Geometry option. After you use Specify, the system shows the status as ACTIVE. If you choose Reinstate before you specify an Avoidance Geometry option, the system displays an error message.</p>
      <p class="para_division">Verify allows you to verify the work coordinate location of an ACTIVE or INACTIVE Avoidance Geometry option. You cannot change the location of an option using Verify.</p>
      <p class="para_division">Redisplay Point allows you to redisplay the specified Avoidance Geometry option. The Avoidance Geometry symbol appears on the display screen at the specified location and remains displayed until the screen is refreshed.</p>
      <p class="para_division">Tool Axis allows you to specify a vector to set the Tool Axis at the Avoidance option location. See the discussion of the Vector Constructor in the Introduction to NX manual.</p>
      <table border="0">
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            <td valign="top" align="left"><img align="left" src="../graphics/note.gif" alt="Note" title="Note"></td>
            <td valign="bottom" align="left" width="100%">
               <div class="para_note">
                  <p class="para_note_body"> NOTE: If you do not specify or activate a Tool Axis, the system automatically assigns the default 0,0,1 tool axis value of the Machining Coordinate System (MCS).</p>
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      </table>
      <div class="title_division">Avoidance Options</div>
      <p class="para_division">The following are the available Avoidance options:</p>
      <div class="title_division">FROM Point</div>
      <p class="para_division">FROM Point defines the initial cutter location at the start of a new segment of cutter path. It does not cause tool movement and it outputs a FROM command as the first entry in the tool path. Therefore, any other post commands will follow the FROM command.</p>
      <p class="para_division">Only one FROM statement is valid for any tool path. It should occur prior to any GOTO commands and will serve as the initial coordinate reference point. Any subsequent FROM commands in the tool path are not passed to GPM.</p>
      <div class="title_division">Start Point</div>
      <p class="para_division">Start Point is a tool positioning location in the cutter path start up sequence that can be used to avoid geometry or fixture components. The Start Point will not output if defined below the Floor Plane.</p>
      <div class="title_division">Return Point</div>
      <p class="para_division">Return Point is a tool positioning location used to control the position of the cutter as it moves away from the part at the end of a cutting sequence.</p>
      <div class="title_division">GOHOME Point</div>
      <p class="para_division">GOHOME Point is the final tool position. The FROM Point is often used as this position. GOHOME Point outputs a GOHOME command as the final entry in the tool path. The postprocessor will always interpret the GOHOME command as a Rapid move. When you select this option you have two additional options:</p>
      <p class="para_division">In addition to the common Avoidance options, you also have the following options when you choose GOHOME Point:</p>
      <p class="para_division">Use FROM Point allows you to position the GOHOME Point in the same location as the FROM Point. The symbol &quot;FR:GH&quot; appears on the display screen at the location of the FROM Point, now also the location of the GOHOME Point. It remains displayed until the screen is refreshed.</p>
      <p class="para_division">GOHOME With No Parameters causes the system to output the postprocessor command move to the GOHOME position without location, values and tool axis.</p>
      <div class="title_division">Clearance Plane</div>
      <p class="para_division">Clearance Plane defines a safe clearance distance for tool motion before and after an operation and during any programmed obstacle avoidance moves between points. The Clearance Plane may be defined as associative or non&ndash;associative to the model geometry.</p>
      <p class="para_division">The status is <b class="uiTerm">NONE</b>, <b class="uiTerm">ACTIVE</b>, or <b class="uiTerm">INACTIVE</b>. <b class="uiTerm">NONE</b> indicates that a clearance plane is not defined. <b class="uiTerm">ACTIVE</b> and <b class="uiTerm">INACTIVE</b> indicate whether or not the Clearance Plane is to be incorporated into the current tool path.
      </p>
      <p class="para_division">If the clearance plane is active, the system generates a rapid move to the clearance plane before the engage move at the start of the operation and retracts to the clearance plane at the end of the operation.</p>
      <p class="para_division">For <b class="uiTerm">Drill</b> operations, the clearance plane may also be used for avoidance moves between CL-points.
      </p>
      <p class="para_division">When using <b class="uiTerm">Verify</b>, the XC, YC, ZC values represent the work coordinates of a point on the clearance plane. The I, J, K values represent the work coordinates of a unit vector perpendicular to the plane.
      </p>
      <div class="title_division">Use At Start and End</div>
      <p class="para_division">Use At Start And End - This option allows you to define the usage of the Clearance Plane you specified.</p>
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            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td">Start And End</p>
            </td>
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td">The system generates a move to the Clearance Plane at both the start and end of the tool path. This is the default status.</p>
            </td>
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         <tr valign="top">
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td">Start Only</p>
            </td>
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td">The system generates a move to the Clearance Plane at the start of the tool path only. At the end of the path, the tool retracts using the specified retract method. If no retract is given, the tool remains on the part surface</p>
            </td>
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         <tr valign="top">
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td">End Only</p>
            </td>
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td">The system generates a move to the Clearance Plane at the end of the tool path only. At the start of the path, the tool engages using the specified engage method. If no engage is given, the first motion output is the first cut motion on the part surface.</p>
            </td>
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            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td">Start Only, Min Clear At End </p>
            </td>
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td">The system generates a move to the Clearance Plane at the beginning of the tool path. At the end, it retracts along the tool axis a distance equal to the Minimum Clearance value specified under the Stock option for that operation. For Surface Contouring, the Check Clearance is used for the Minimum Clearance.</p>
            </td>
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            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td">End Only, Min Clear At Start</p>
            </td>
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td">The system generates a move to the Clearance Plane at the end of the tool path. The tool path begins with an engage move along the tool axis a distance equal to the Minimum Clearance value specified under the Stock option for that operation. For Surface Contouring, the Check Clearance is used for the Minimum Clearance.</p>
            </td>
         </tr>
      </table><br><table border="0">
         <tr>
            <td valign="top" align="left"><img align="left" src="../graphics/note.gif" alt="Note" title="Note"></td>
            <td valign="bottom" align="left" width="100%">
               <div class="para_note">
                  <p class="para_note_body"> NOTE: The motions from and to the Clearance Plane will generally be long the tool axis. The only exception is when the Clearance Plane is perpendicular to the Floor Plane. The motions will be perpendicular to the Clearance Plane.</p>
               </div>
            </td>
         </tr>
      </table>
      <table border="0">
         <tr>
            <td valign="top" align="left"><img align="left" src="../graphics/note.gif" alt="Note" title="Note"></td>
            <td valign="bottom" align="left" width="100%">
               <div class="para_note">
                  <p class="para_note_body">The clearance plane and lower limit planes may be inherited from a geometry group, This allows several operations to share the same clearance plane. If you specify the clearance plane in avoidance, then the inheritance is turned off. If you change your mind and want to use the plane in the group, then you need to go to the inheritance list and turn the inheritance back on.</p>
               </div>
            </td>
         </tr>
      </table>
      <p class="para_division">The ZC option allows you to specify the Clearance Plane in terms of a distance from the work plane (XC-YC). The system creates a plane parallel to the XC-YC plane at the specified distance along the ZC axis.</p>
      <div class="title_division">Lower Limit Plane</div>
      <p class="para_division">Lower Limit Plane defines the lower limit of cutting and non cutting tool motions. The normal vector defines the &quot;above&quot; side of the plane and should point toward the tool holder. When the tool violates the Lower Limit Plane by attempting to position to the &quot;lower&quot; side (the side of the plane opposite the normal vector) , you have several Actions available; a warning can be issued to the tool path and CLSF, the system can adjust the points upward, or omit them altogether. The actions available depend on the submodule.</p>
      <p class="para_division">The <b class="uiTerm">Action</b> option toggles between the following.
      </p>
      <table cellspacing="3" align="center">
         <tr valign="top">
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td"><b class="uiTerm">Warning Only</b></p>
            </td>
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td">The the GOTOs are not affected. The tool motion is not altered and is allowed to violate the Lower Limit Plane, but a warning is written to the tool path and CLSF.</p>
            </td>
         </tr>
         <tr valign="top">
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td"><b class="uiTerm">Normal To Plane</b></p>
            </td>
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td">A warning is displayed and the violating GOTOs are projected to the Lower Limit Plane, in a direction normal to the Lower Limit Plane. The violating tool motion is omitted.</p>
            </td>
         </tr>
         <tr valign="top">
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td"><b class="uiTerm">Along Tool Axis</b></p>
            </td>
            <td bgcolor="#f4f4f4" colspan="1" rowspan="1">
               <p class="para_td">A warning is displayed and the tool violating GOTOs are projected to the Lower Limit Plane, in a direction along their respective tool axis. The violating tool motion is omitted. This allows the tool to follow the contour of the part to the point of intersection between the part and the lower limit plane.</p>
            </td>
         </tr>
         <tr>
            <td bgcolor="#F4F4F4" colspan="1" rowspan="1" valign="top">
               <p class="para_td"><b class="uiTerm">Limit Point</b> (<b class="uiTerm">Drill</b> operations only)
               </p>
            </td>
            <td bgcolor="#F4F4F4" colspan="1" rowspan="1" valign="top">
               <p class="para_td">&nbsp;If a point is below Lower Limit Plane, the point is omitted. If point is on the Lower Limit Plane, and FEDTO causes a violation, FEDTO is adjusted to reach the Lower Limit Plane.</p>
            </td>
         </tr>
      </table><br><p class="para_division">The Flip Normal to Plane suboption reverses the normal vector of the defined Lower Limit Plane. This vector defines the &quot;above&quot; side of the plane and should point toward the tool holder.</p>
      <p class="para_division">The ZC suboption allows you to specify the Lower Limit Plane in terms of a distance from the work plane (XC-YC). The system creates a plane parallel to the XC-YC work plane at the specified distance along the ZC axis.</p>
      <table border="0">
         <tr>
            <td valign="top" align="left"><img align="left" src="../graphics/note.gif" alt="Note" title="Note"></td>
            <td valign="bottom" align="left" width="100%">
               <div class="para_note">
                  <p class="para_note_body"> NOTE: The cutter will probably gouge the Lower Limit Plane when you use either projection method and the tool axis is not normal to the Lower Limit Plane.</p>
               </div>
            </td>
         </tr>
      </table>
      <div class="title_division">Redisplay Avoidance Geometry</div>
      <p class="para_division">Redisplay Avoidance Geometry is the method used to redisplay the points and plane symbols in the Floor plane, if they are active. This option also displays the current Reference Coordinate System (RCS).</p>
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