Creating Bitangent Shape Fillets

This task shows how to create a shape fillet between two surfaces.
The fillet surface is obtained by rolling a sphere between the selected surfaces.
This command also lets you create tritangent shape fillets.
  This task also shows you how to create different types of variable radius fillets.

Open the ShapeFillet1.CATPart document.

  1. Click Shape Fillet .

    The Fillet Definition dialog box appears.
  2. Choose the BiTangent Fillet type.

  3. Select a surface as the first support element.

  4. Select another surface as the second support element.

  5. Enter the value of the fillet Radius.

    Up to four fillet locations may be possible.
    To help you decide on the location an arrow is displayed on each selected surface. You can click on the arrows to specify the desired fillet location.
    If the user selects the Chordal option, the Radius parameter changes to Length. For additional information refer Creating Chordal Fillets.
  6. Select the Conic parameter check box. This check box allows you to vary the section of the fillet.

    For parameter equal to:
    •  0.5, the resulting curve is a parabola.
    • 0 < parameter < 0.5, the resulting curve is an arc of an ellipse
    • 0.5 < parameter < 1, the resulting curve is a hyperbola.
  7. Use the combo to choose the desired type of Extremities for the fillet:

    • Smooth: a tangency constraint is imposed at the connection between the fillet surface and the support surfaces, thus smoothing the connection.
    • Straight: no tangency constraint is imposed at the connecting point between the fillet and the initial supports, generating sometimes a sharp angle.
    • Maximum: the fillet surface is limited by the longest selected support's edge.
    • Minimum: the fillet surface is limited by the shortest selected support's edge.
  8. Click Preview to see the filleted surface:

  9. Click OK to create the shape fillet.

    The surface (identified as is added to the specification tree.
    • In case the selected supports are partially tangent, it is advisable to create an edge fillet.
    • Parameters can be edited in the 3D geometry. To have further information, refer to Editing Parameters.

Creating a Variable Radius Fillet

With Spine and Hold Curve

Open the ShapeFillet3.CATPart document.



You can generate a variable bi-tangent radius fillet by selecting a Hold curve. In this case, you need to select a previously defined limiting curve that will control the fillet radius, and a previously defined spine that defines the planes in which the filleted surface section will pass. Both these curves must be larger than the surfaces involved, and the Hold curve must lie on one of these initial surfaces. The resulting filleted surface is tangent to the initially selected surfaces and limited by the hold curve.
  See also Creating a variable bi-tangent circle radius fillets using a spine.

With Laws and Relimiters


The Law button becomes available when the Spine field is filled in.

Open the ShapeFillet3.CATPart document.
  1. Select two surfaces.

  2. Select Line.1 as the spine.

    Law relimiters are displayed on each extremity of the spine to delimit the radius law range. Manipulators enable you to move them along the spine.

    You can use a close spine, in that case, only the Law Relimiter 1 field is enabled.
  3. Click Law... to display the Law Definition dialog box. In this case, you need to select a law as defined in Creating Laws.

    The 2D viewer enables you to preview the law evolution before applying it.
    The Law Viewer allows you to:
    • visualize the law evolution and the maximum and minimum values,
    • navigate into the viewer by panning and zooming (using to the mouse),
    • trace the law coordinates by using the manipulator,
    • change the viewer size by changing the panel size
    • reframe on by using the viewer contextual menu
    • change the law evaluation step by using the viewer contextual menu (from 0.1 (10 evaluations) to 0.001 (1000 evaluations)).
    You can check Inverse law to reverse the law as defined using the above options.
  4. Enter Start value and End value.

  5. Choose the type of law to be applied to the radius.

    Five basic or advanced types are available:
    • Constant: a regular law, only one value is needed.
    • Linear: a linear progression law between the Start and End indicated values.
    • S type: an S-shaped law between the two indicated values. The pitch distance will vary between these two pitch values.
    • Advanced: allowing to select a Law element as defined in Creating Laws.
    • Implicit: allowing the selection of points on the spine the association of values for these points.

      a. Select points on the spine. By default, the spine extremities (relimiters) are selected.

      b. Define a radius for each point. For instance, set 30mm for Point.2 and 60 for Point.3.
      The radius law applies between these two points. The radius values are interpolated into a curvature continuous radius law defined over the whole spine curve.

      c. Create a third point between Point.2 and Point.3 with a radius of 90mm.



      d. Define the Interpolation Mode: Linear (straight interpolation) or Cubic (smooth interpolation). Here we chose the Linear mode.

  6. Click Close to return to the Fillet Definition dialog box.

  7. Click Preview to see the filleted surface:

    • The spine curve must be curvature continuous.

    • At least two points must be selected on the spine.

    • If the spine is closed, only one point is selected.

    • You can edit a point, by right-clicking it and choosing the Edit Point contextual item.

    • You can add a point by right-clicking and choosing the Create Point contextual item.

    • Points are automatically reordered in the list, according to their ratio on the spine.


BiTangent Fillet with Multi-ribbons

  Faces to keep lets you manage multi-ribbons.
Open the ShapeFillet2.CATPart document.
  1. Select two surfaces.

  2. Set the Radius value as 20.

  3. Click Preview.

    As you selected two ribbons, an error message pops up asking you to process each ribbon in a separate operation.
  4. Click OK in the dialog box.

    The solutions are shown in red:
  5. In the Faces to keep field, select the face(s) you want to keep to create the shape fillet.

  6. Click Preview to see the filleted surface.

You can deselect Trim support1 and Trim support 2. In this case, the support element involved will not be trimmed and assembled to the filleted surface.
By default, both options are checked, thus relimiting both support elements.
In the examples below, we changed the filleted surface's color to better visualize it.

  With only one support element trimmed: With both support elements trimmed:
A trim is automatically performed when using the Generative Shape Design 1 product.