Extrapolating Curves

This task explains how to modify a curve, or surface boundary, by extrapolation, that is by modification of its length. It can be a positive or negative extrapolation meaning that you can actually lengthen or shorten the curve. This command works in mono-selection.

Open the FreeStyle_Part_51.CATPart document.

  1. Select the curve to be extrapolated.
    It will be extrapolated on the end-point side closest to the selection point.

  2. Click Styling Extrapolate .
 

The Extrapolation dialog box is displayed.

  • Element: Select the element to be extrapolated.
  • Limit Type: Two options are available:
    • Length: Specify the length for extrapolation.
    • Up To: Specify the element up to which you want the input element to be extrapolated. You can select a curve, plane or surface.
  • Length: This field is displayed if Length option is selected in the Limit Type list. Enter the extrapolation length.
    You can create a styling extrapolate by setting the values for the length parameters.
    To set the step value for the length parameters:

             1. Right-click the box and select Change step.

             2. Select the value.

     
    You can enter a new step value in the New step dialog box by selecting new one.

             1. Right-click the box and select Change step > new one.

                 The new step dialog box appears.
               
             2. In the box, type a new step value.
             3. Click OK.

    To calculate minimum distance between geometrical entities (Measure Between) and calculate property of any geometrical entity (Measure Item):

    1. Right-click the box and select Measure Between.
             OR
    2. Right-click the box and select Measure Item.

    To set the range value for the length parameters:

            1. Right-click the box and select Range > Edit.

               The Range definition dialog box appears.
              

           2. In the Inf. Range box, type a value.

            3. In the Sup. Range box, type a value.
           4. Click OK.


        To add range values perform the following actions: 

           1. Right-click the box and select Range > Suppress.

           2. Right-click Length box and select Add Range….

               The Range definition dialog box appears.
              

     

           3. Select the Inf. Range check box and Sup. Range check box.

            4. Enter the range values and click OK. 
     
    The default Range, Step and Value of the Length scroll bar in Styling Extrapolate command are as follows:
    Scroll Bar Name Range Step Value
    Length Scroll Bar -1e+006 mm  to 1e+006 mm  0.1 mm 0 mm

  • Up To: This field is displayed if Up To option is selected in the Limit Type list. Select the limiting element.
    You can also create limiting plane element using the contextual menu command. Following commands are available:
    Create Plane
    XY Plane
    YZ Plane
    ZX Plane
  • Type: Two options are available:
    • Tangential: the surface is extended along the tangent to the surface on the selected boundary and of a given distance (G1 continuity).
    • Curvature: the surface is extrapolated by the specified value, complying with the surface curvature (G2 continuity). No manipulator is displayed.
  • Exact: This option is not available for curves.

  1. Select the Tangential option:
    The curve is extrapolated taking into account the keyed in length (expressed in model units).
    Here we keyed in 100.

  
 

 

If you key in a negative value, the resulting curve is created in the other direction.

  
 

 

  1. Click OK to create the extrapolated curve.

  • You can also use the manipulators to interactively modify the value.
  • The curvilinear length of the extrapolation is displayed.
  • Capabilities are available from:
    • the contextual menu when right-clicking an end point.
    • the dashboard: auto detection, attenuation