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      <title>Drive Geometry</title>
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      <div class="title_topic5" id="xps10_pagetitle">Drive Geometry</div>
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      <p class="para_topic">The available Drive Geometry options enable you to select and edit faces.</p>
      <p class="para_topic">Edit displays the Edit Drive Geometry dialog allowing you to add or subtract faces for Drive Geometry and the parameters associated with each face.</p>
      <p class="para_topic">Select displays the Drive Geometry dialog allowing you to initially define the Drive Geometry. Reselect enables you to redefine the Drive Geometry. The options found in the Drive Geometry dialog box are similar to those found in the Part, Check, and Blank Geometry dialog boxes, however, most of these options are not available when defining Drive Geometry.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/matside_drv_vectr.gif"></p>
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      <div class="title_figure">Material Side and Drive Direction Vectors</div>
      <p class="para_topic">Refer to the introduction of this section and to the beginning of the discussion on Surface Area Drive Method details on Drive Geometry and how to select single and multiple faces.</p>
      <p class="para_topic">Display highlights the Drive Geometry you previously specified.</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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               <div class="para_note">
                  <p class="para_note_body"> NOTE: Only Faces is available under Selection Options. All other entity types are blanked out when defining Drive Geometry. Expand Item is also unavailable when defining Drive Geometry.</p>
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      <div class="title_division">Surface Stock</div>
      <p class="para_division">Surface Stock allows you to offset Drive Points along surface normals a specified distance.</p><a name="surface-area_tool_position"></a><div class="title_division">Tool Position</div>
      <p class="para_division">Tool Position determines how the system calculates contact points on the Part Surfaces. The tool positions to the Part Surfaces by following the Projection Vector from the Drive Point. Tanto creates Part Surface contact points by first positioning the tool tangent to the Drive Surface and then projecting along the Projection Vector to the Part Surface, where the Part Surface contact point is calculated. On creates Part Surface contact points by first positioning the tip of the tool directly on the Drive Points and then projecting along the Projection Vector to the Part surface, where the contact point is calculated.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/tanto_on-toolpostn.gif"></p>
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      <div class="title_figure">Tanto and On Tool Position</div>
      <p class="para_division">Tanto is generally useful for maximum Part Surface cleanup. You will get greater coverage on steep surfaces.</p>
      <p class="para_division">When creating a Tool Path directly on the Drive Surface (with no Part Surface defined), Tool Position should be toggled to the Tanto position. Depending on the Tool Axis used, On may violate the Drive Surface as illustrated below.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/tanto_cutdrvsurf.gif"></p>
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      <div class="title_figure">Tanto when Cutting Drive Surfaces</div>
      <p class="para_division">Tanto should be used when the same surfaces have been defined as both the Drive Surfaces and Part Surfaces.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/tanto_on_drvpt_same.gif"></p>
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      <div class="title_figure">Tanto and On when Drive and Part are Same Surface</div>
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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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               <div class="para_warning">
                  <p class="para_warning_body">  CAUTION: When you use the Tanto position method the Tool Path is calculated from the point on the tool that touches the cutting surface. As the tool moves along the surface the contact point on the tool will change as the shape of the surface changes. The display shows the path of the tool endpoint and not necessarily the cutting point of the tool.</p>
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      <p class="para_division">Since the cutting position on the tool may change and it is not necessarily represented by the Tool Path, the operation may appear to retrace, spike, or gouge. This condition may occur when you are machining a part where the radius of curvature of the Part Surface is smaller than the nose radius of the tool or when two surfaces meet at a concave corner. Changing your view of the tool path will reveal that the Part Surface is not being violated.</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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               <div class="para_note">
                  <p class="para_note_body"> NOTE: You must use Tanto if the Stepover Method is set to Scallop Height. On is blanked out.</p>
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      <div class="title_division">Cut Direction</div>
      <p class="para_division">Cut Direction allows you to specify the cut direction and the quadrant where the first cut will begin. It is specified by selecting one of the vector arrows which appear in pairs at each of the surface corners.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/vector_spec_dirctn.gif"></p>
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      <div class="title_figure">Selected Vector Specifies Cut Direction</div>
      <div class="title_division">Flip Material</div>
      <p class="para_division">Flip Material allows you to reverse the direction of the Material Side normal vector of the Drive Surface. This vector determines which side of the Drive Surface the tool contacts as it follows the Drive Path (Surface Area Drive Method only). &nbsp;The Material Side normal vector must point toward the material to be removed and away from the side that the tool cannot violate as illustrated below.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/matsidevectr.gif"></p>
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      <div class="title_figure">Material Side Vector</div>
      <p class="para_division">Note:</p>
      <ul>
         <li>
            <p class="para_item">When there is no Part Geometry, the Tool Path follows the Drive Path exactly, and the Material Side of the Drive Surface becomes the Tool Path's machining side.</p>
         </li>
         <li>
            <p class="para_item">When there is Part Geometry, the Tool Path is projected from the Drive Path and the Projection Vector determines the Tool Path's machining side. There are several options for computing Projection Vector and some of these options, such as Normal to Drive, use the Material Side normal vector in their calculations. &nbsp;Please refer to the Projection Vector section for more details.</p>
         </li>
      </ul>
      <div class="title_division">Shape of Trimmed Surfaces</div>
      <p class="para_division">When the drive surface is made up of trimmed surfaces, their shape is important because it determines the desired output. &nbsp;We recommend a rectangular shape. &nbsp;</p>
      <p class="para_division">In the situation where the trimmed surfaces are not rectangular, the system attempts to resolve this for you. &nbsp;Although this mapping (to rectangular topology) mechanism is fairly effective for simple trimmed faces, it may fail in the following situations:</p>
      <ul>
         <li>
            <p class="para_item">When there are less than 4 sides in the trimmed face</p>
         </li>
         <li>
            <p class="para_item">When there are much more than 4 sides in the trimmed face, and the shape is very irregular</p>
         </li>
      </ul>
      <p class="para_division">When the mapping mechanism fails, the system uses the untrimmed underline surface instead.</p>
      <div class="title_division">Work Around</div>
      <p class="para_division">There is a general work around, but it does require some modeling work.</p>
      <p class="para_division">You can gain control over the surface by splitting it at strategic places into smaller surfaces. You can do this in modeling:</p>
      <p class="para_division">Modeling &rarr; Insert &rarr; Feature Operation &rarr; Split.</p>
      <p class="para_division">First, Split needs a plane to split. &nbsp;A general way to define the plane is to construct 3 points that define the plane. &nbsp;Before going into Split, define your 3 points:</p>
      <p class="para_division">&nbsp;&nbsp;&nbsp;1. Find a corner on the trim boundary that looks like it will cause trouble and construct a point there.</p>
      <p class="para_division">&nbsp;&nbsp;&nbsp;2. Construct a point on the opposite boundary by the end point of a curve or points on a curve.</p>
      <p class="para_division">&nbsp;&nbsp;&nbsp;3. Translate one of the two points up off the surface in the direction approximately normal to the surface.</p>
      <p class="para_division">The goal is to use one or more splits to break up the surface into rectangular parts so that they can be put into a grid.</p>
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