Creating Chordal Fillets  

The Chordal Fillet command is used to control the width of the fillet (distance between the 2 rolling edges) which is also called as chordal length.

          

This command allows you to define two types of variation in the chordal fillet:

  • Cubic
  • Linear

This task shows you how to create chordal fillets.

Open the Chordal_Fillet.CATPart document.
To perform this task in a different workbench like FMP, create a cube.

  1. Click Chordal Fillet in the Dress-Up Features toolbar (Fillets sub-toolbar). 
    The Chordal Fillet Definition dialog box is displayed. The default options let you define a cubic variation of the chordal fillet.

For Part Design workbench, click Chordal Fillet .

For Generative Shape Design workbench, click Chordal Fillet .

The Support and Extremities fields are not seen in the Part Design workbench.
 

  1. Select the edge to be filleted. You can define chordal fillets on closed edges.
    The application detects both the vertices and displays two identical chordal lengths.

  2. Double-click the chordal length to access the Parameter Definition dialog box. For example, enter 50mm.

  3. Click OK in the Parameter Definition dialog box.

  4. Click the icon of the Points field in the Chordal Fillet Definition dialog box. Select Variable_Plane in the specification tree or geometry.

You can define a fillet with variable width by specifying the intermediate points.
 

  1. Double-click Variable_Plane chordal length in geometry. For example, enter 20mm in the Parameter Definition dialog box.

  2. Click OK in Chordal Fillet Definition dialog box. The chordal fillet is created as seen:

You can select the Conic parameter check box. This option allows you to vary the section of the fillet.
For a parameter between or 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.

  • Conical fillets do not handle twist configurations. If a twist is detected, the fillet operation fails.

  • If the fillet surface curvature is lower than the support curvature, fillet surface relimitation may fail. In such cases, the conic parameter has to be decreased.

Limiting Elements

  1. To edit this fillet, double-click EdgeFillet.1 in the specification tree or geometry. Click the More>> button to access the Limiting element(s) option.

  2. Click the icon of Limiting element(s) field. Select Limit_Plane in the specification tree or geometry.
You can click the arrow to reverse the direction and therefore specify the portion of material that is to be kept.
 

  1. Click OK. The variable radius fillet is trimmed to Limit_Plane. The final part looks like this:

  • The chord length is measured using the isoparams (circular arcs).

  • The fillet surface respects the specified chord length. The chord length is measured using the circular arcs.

  • Some faces are created to correct the twists. In such a case, the corresponding warning message is displayed. Such untwisted surfaces in general do not satisfy the chord length constraint.

  • The constant chordal fillet should end in a tip, if the support surfaces are becoming tangent.

  • The constant chordal fillet cannot compute a fillet, if the support surfaces become tangent.

  • You should use variable chordal fillet with very small /zero radius at the location where the support surfaces become tangent. Constant chord fillet cannot handle such cases.
 

Chordal Fillet Dialog Box

Points

  • Contextual commands for creating the points you need are available from the Points field. Right-click in the Points field to see the contextual menu:

    • Create Point: For more information, see Creating Points.

    • Create Midpoint: Creates the midpoint of the line you select.

    • Create Endpoint: Creates the endpoint of the line you select.

    • Create Plane: For more information, see Creating Planes.

    • Create Intersection: For more information, see Creating Intersections.

    • Create Projection: For more information, see Creating Projections.
      If you create any of these elements, the application displays the corresponding element detail in the Points field. Click the icon of the Points field to edit the corresponding element.

  • To add additional points on the edge to be filleted, you can also select planes. The application computes the intersections between these planes and the edge to determine the useful points.

  • Points can also be added by selecting the 3D points.

Limiting Elements

  • It is possible to use one or more limiting elements.

  • Contextual commands for creating the limiting elements you need are available in the Limiting element(s) field. Right-click in the Limiting element(s) field to see the contextual menu:

    • Create Point: For more information, see Creating Points.

    • Create Midpoint: Creates the midpoint of the line you select.

    • Create Endpoint: Creates the endpoint of the line you select.

    • Create Plane: For more information, see Creating Planes.

    • XY Plane: The XY plane of the current coordinate system origin (0,0,0) becomes the limiting element.

    • YZ Plane: The YZ plane of the current coordinate system origin (0,0,0) becomes the limiting element.

    • ZX Plane: The ZX plane of the current coordinate system origin (0,0,0) becomes the limiting element.

    If you create any of these elements, the application displays the corresponding element detail in the Limiting element(s) field. Click the icon of the Points field to edit the corresponding element.

  • You can create limiting elements by clicking the edge to be filleted. The application displays this element as a blue disk.

  • You can select points as limiting elements. These points must be located on the edge to be filleted and they must have been created using the On curve option available in the Point Definition dialog box.