Creating Blended Surfaces

This task shows how to create a blended surface, that is a surface between two wireframe elements, taking a number of constraints into account, such as tension, continuity, and so forth.
Note that curves with one edge only can be used to create blend surfaces.

Open the Blend1.CATPart document.

  1. Click Blend .

    The Blend Definition dialog box appears.
  2. Successively select the first curve and its support, then the second curve and its support.
    These can be surface edges, or any curve.

  3. Set the continuity type using the Basic tab.

    It defines the continuity connection between the newly created surface and the curves on which it lies.

    The illustration above, shows the Tangency continuity, and the following illustrations show the Point and Curvature continuity types:

    Point continuity on both limits Curvature continuity on both limits
  4. Check Trim first support/Trim second support, on one or both support surfaces to trim them by the curve and assemble them to the blend surface.

    By default the blend surface borders are tangent to the support surface borders.
    You can also specify whether and where the blend boundaries must be tangent to the supports boundaries:
    • Both extremities: the tangency constraint applies at both ends of the curve
    • None: the tangency constraint is disregarded 
    • Start extremity only: the tangency constraint applies at the start point of the curve only
    • End extremity only: the tangency constraint applies at the end point of the curve only
    The Start and End extremities are defined according to the arrows in the blended surface's preview.
  5. Set the tension type using the Tension tab.

    It defines the tension of the blend at its limits and can be set for each limit independently
    It can be Constant or Linear. A third tension type is available: S Type. It enables to set a variable tension.

  6. Click OK to create the blended surface.

    The surface (identified as is added to the specification tree.
    • Selecting a support is not compulsory.
    • You can create closing points using the contextual menu on the First or Second closing point fields in the dialog box, or using the contextual menu directly on one of the selected curves.
    • Use the Replace, Remove, or Reverse buttons, to manage the selected elements (curves, support, closing and coupling points).
    • You can also use the contextual menu on the texts displayed on the geometry to set the continuities, trim the supports or manage the curves and support in general.