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      <title>Surface Area Drive Method</title>
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      <div class="title_topic5" id="xps10_pagetitle">Surface Area Drive Method</div>
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      <p class="para_topic">The Surface Area Drive Method enables you to create an array of Drive Points that lie on a grid of Drive Surfaces. This Drive Method is useful in machining very complex surfaces requiring a variable Tool Axis. It provides additional control of both the Tool Axis and the Projection vector.</p>
      <p class="para_topic">The Tool Path is created on the selected Part Surfaces by projecting points from the Drive Surfaces in the direction of a specified Projection Vector. If Part Surfaces are not defined, the Tool Path can be created directly on the Drive Surfaces. The Drive Surfaces need not be planar, but must be arranged in an orderly grid of rows and columns. Adjacent surfaces must share a common edge and may not contain gaps that exceed the Chaining Tolerance defined under Preferences. Trimmed surfaces can be used to define Drive Surfaces as long as the trimmed surface has four sides. Each side of the trimmed surface can be a single edge curve or comprised of multiple tangent edge curves that can be thought of as a single curve.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/surfcont_sfi09.gif"></p>
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      <div class="title_figure">Even Rectangular Grid of Rows and Columns</div>
      <p class="para_topic">The Surface Area Drive Method will not accept Drive Surfaces that are arranged in uneven rows and columns or that have gaps that exceed the Chaining Tolerance as illustrated below.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/surfcont_sfi08.gif"></p>
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      <div class="title_figure">Uneven Rows and Columns</div>
      <p class="para_topic">The Surface Area Drive Method provides maximum control of the Tool Axis. Variable tool axis options become available which allow you to define the Tool Axis relative to the Drive Surfaces. Additional Tool Axis control is sometimes necessary to prevent excessive tool undulations when machining very contoured Part Surfaces as illustrated below.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/surfcont_sfi07.gif"></p>
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      <div class="title_figure">Tool Axis Movement using Normal to Drive</div>
      <p class="para_topic">In some cases, as illustrated above, Drive Surfaces are created specifically to control the Tool Axis. In other cases, as illustrated below, existing surfaces are used as Drive Surfaces.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/surfcont_sfi06.gif"></p>
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      <div class="title_figure">Tool Axis Movement using Normal to Drive</div>
      <p class="para_topic">The Surface Area Drive Method also provides maximum control of the Projection Vector. An additional Projection Vector option, Normal to Drive, is available. This option enables you to evenly distribute Drive Points on to very convex Part Surfaces (Part Surfaces whose relative normals exceed 180 degrees). Unlike a boundary, Drive Surfaces can be designed to wrap around the part surfaces to project Drive Points evenly on to all sides of the part as illustrated below.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/surfcont_figuressc29.gif"></p>
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      <div class="title_figure">Projection Vector is Normal to Drive Surface</div>
      <p class="para_topic">If the surfaces you wish to machine meet the criteria for Drive Surfaces (arranged in an orderly grid with no gaps) it may be preferable to generate a Tool Path directly on the Drive Surfaces by not selecting any Part geometry. Because Drive Points are not projected on to Part Surfaces, the Projection Vector definition becomes irrelevant. The Material Side vector direction determines which side the tool contacts when cutting directly on the Drive Surfaces. Material Side Vector should point towards the material to be removed.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/surfcont_figuressc30.gif"></p>
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      <div class="title_figure">Tool Path on Drive Surfaces</div>
      <p class="para_topic">When creating a Tool Path directly on the Drive Surface, Tool Position should be toggled to Tanto. 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/surfcont_figuressc31.gif"></p>
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      <div class="title_figure">Tool Position Should be Tanto when Machining Drive Surfaces</div>
      <p class="para_topic">Drive Surfaces must be selected in an orderly sequence. They may not be selected randomly. The sequence in which you select adjacent surfaces defines the rows. When you finish selecting the first row, you must specify that you wish to begin selecting the next row. You must then select the second row of surfaces and all subsequent rows in the same order as the first.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/surfcont_figuressc32.gif"></p>
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      <div class="title_figure">Drive Surface Selection Sequence</div>
      <p class="para_topic">You must specify that you wish to begin selecting the next row of surfaces after selecting the first row by choosing the Select Next Row button. In the figure above, you must specify that you wish to begin selecting the next row only after selecting surfaces 1-4. This allows the system to establish the number of surfaces in each row. Each subsequent row expects the same number of surfaces as the first. The system indicates the number of rows in the Status message bar as you add Drive Surfaces.</p>
      <p class="para_topic">Once you have selected the Drive Surfaces, the system displays a default Drive Direction Vector as illustrated below. You may redefine the Drive Direction by selecting Cut Direction and then selecting one of eight displayed vectors which appear in pairs at each of the surface corners. The selected vector specifies the Drive Direction and the quadrant where the first cut will begin.</p>
      <div class="figure">
         <p align="center"><img align="bottom" src="graphics/surfcont_sfi01.gif"></p>
      </div>
      <div class="title_figure">Material Side and Drive Direction Vectors</div>
      <p class="para_topic">The system also displays a Material Side Vector. The Material Side Vector should point towards the material to be removed as illustrated above. To reverse this vector, select Flip Material in the Surface Drive Method dialog box.</p>
      <p class="para_topic">The following options display in the Surface Drive Method dialog box.</p>
      <table border="1" cellspacing="0" align="center">
         <tr>
            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">Drive Geomety</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Defines Drive Geometry by selecting faces</p>
            </td>
         </tr>
         <tr>
            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">Surface Stock</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Offsets Drive Points along surface nor mals a specified distance</p>
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            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">Tool Position</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Determines how the system calculates contact points on the Part Surfaces</p>
            </td>
         </tr>
         <tr>
            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">Cut Direction</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Specifies the cut direction and the quad rant where the first cut will begin</p>
            </td>
         </tr>
         <tr>
            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">Flip Material</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Reverses the direction of the Material Side Vector of the Drive Surface</p>
            </td>
         </tr>
         <tr>
            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">Cut Area</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Defines how much of the total Drive Surface area to utilize in the operation by specifying Surface Percentages or Di agonal Points</p>
            </td>
         </tr>
         <tr>
            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">Pattern</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Defines the shape of the tool path</p>
            </td>
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            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">Cut Type</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Defines how the cutter moves from one cut pass to the next</p>
            </td>
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         <tr>
            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">Cut Step</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Controls the distance between Drive Points in the cut direction</p>
            </td>
         </tr>
         <tr>
            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">Stepover</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Controls the distance between successive Cut Passes</p>
            </td>
         </tr>
         <tr>
            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">When Gouging</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Specifies how the system will respond when the tool gouges the Drive Surface during cutting moves</p>
            </td>
         </tr>
         <tr>
            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">Tool Axis</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Changes the tool axis specified earlier or specifies a Tool Axis available only in the Surface Area Drive Method</p>
            </td>
         </tr>
         <tr>
            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">Projection Vector</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Determines how the Drive Points project to the part surface</p>
            </td>
         </tr>
         <tr>
            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">Display Contact Points</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Displays a surface normal vector at each of the Drive Points that has been generated</p>
            </td>
         </tr>
         <tr>
            <th colspan="1" rowspan="1" valign="top">
               <p class="para_th">Display Drive Path</p>
            </th>
            <td colspan="1" rowspan="1" valign="top">
               <p class="para_td">Displays the Drive Path generated ac cording to the specified drive parameters.</p>
            </td>
         </tr>
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