Tips & Tricks: Tangency Propagation in Creo FMX

With Creo Parametric Flexible Modeling Extension (FMX), you can easily modify geometry  by simply selecting and dragging. But what happens to neighboring surfaces? Especially those with a tangential connection to the surface you’re modifying?

Among the enhancements in Creo 3.0, you can now maintain those tangent connections. The following video demonstrates:

To try it yourself, follow these steps:

  1. Click the Flexible Modeling tab, and select the geometry that you plan to modify.

Selected geometry appears in green.


  1. In this example, we want to increase the radius of the selected cylinder. To to this, in the Transform group, click Offset (Note, you could also use Move, Substitute, or Modify Analytic.)
  1. In the Offset tool dashboard, select the icon with a curved surface and an arrow.

This enables tangency control, which allows you to maintain the existing tangency to surfaces directly adjacent to the geometry that is being modified. This means that the neighboring surfaces will be adjusted along with the primary surface to maintain the tangential connection.

Here you can see that the tangential surfaces adjacent to the primary surface are highlighted in pink.

The system automatically applies some default conditions to the neighboring geometry so you maintain tangency. Need more control?

To apply user-defined conditions, follow these steps:

  1. In the feature dashboard, click the Conditions tab, and clear the Create default conditions check box.
  2. Right-click the graphics window, and click Add condition to open the Conditions dialog box.
  3. Select an edge as a Reference, select Fixed from the Applicable Conditions, and then click OK.  The new condition will appear in Conditions

In this example the reference’s condition is set to Fixed.

Note. You can fix surfaces, edges, or axes, specify what tangencies should be maintained or lost, and maintain constant radii.

User-defined conditions can also be created by right clicking the applicable reference, and selecting from the Right Mouse Button menu. For example, you can right click on a cylindrical surface and select Fixed with Tangency to add a condition.

To see more video demos like the one above, visit the PTC University Learning Exchange. Note that you may need to create an account if you don’t already have one. The good news is that it’s free, and after creating your new login, you’ll find more than hundreds of in-depth demonstrations and tutorials for Creo.

You can also join a discussion of tangency propagation in Creo FMX in this Community forum post and in PTC’s Help pages too.