Constructing lofted synchronous features

You can use the Lofted Protrusion, Lofted Surface, Lofted Cutout, and BlueSurf commands to create lofted features.

Lofted features are constructed by extruding two or more cross sections to construct a feature.

Similar to the swept commands, you can define the cross sections by:

You can also use a curve, known as a guide curve, to define a path between the cross sections of the loft. The end condition options allow you to control the shape of the loft feature where it meets the first and last cross sections.

Because loft features are often used to define aesthetic elements in a model, you may want to experiment with different settings to achieve the results you want.

Note:

You can construct a loft feature with the BlueSurf command that contains only one cross section and one guide curve.

Cross Sections

The cross sections must be closed when constructing a lofted protrusion or lofted cutout, but they can be open when constructing a lofted surface or a BlueSurf feature. You can use planar or non-planar cross sections when constructing lofted features. A non-planar cross section can be constructed using the Intersection Curve command or you can use a part edge that is non-planar.

As you define each cross section, you must select the start point for non-periodic cross sections. You define the start points (A), (B), (C) by positioning the cursor over a vertex when you select each cross section. Defining appropriate start points allows you to prevent or control twisting. In some cases, mismatched start points can result in failed features.

Vertex Mapping

Vertex mapping allows you to define sets of map points between the cross sections of a loft or swept feature. A default vertex map set is defined by the start point for each cross section you select. The Vertex Mapping button, available on the command bar during the Extent Step, allows you to redefine the start point for a cross section or to define additional vertex mapping sets.

Defining additional sets of vertex map points can be helpful for lofts and sweeps where there are different numbers of elements in each cross section. This can sometimes result in undesirable twisting of the feature or feature failure.

For example, a simple loft between a triangular sketch and a rectangular sketch will result in twisting (A). Defining additional vertex map sets allows you to eliminate the twisting (B). Notice that it is valid to use the same sketch vertex in more than one map set, as in sets 1 and 2.

Guide Curves

Guide curves (A) (B) allow you to control the shape of a lofted or swept surface between the cross sections. You can use a sketch, the edge of an adjacent surface, or a curve that has been projected onto a surface as guide curves.

The shape of a lofted surface with the same cross section elements changes depending on whether there are no guide curves, one guide curve, or more than one guide curves.

When you use a sketch as a guide curve, you can edit the sketch to change the shape of the feature.

End Conditions

You can control end conditions, the shape of the loft feature where it meets the first and last cross sections, with several options. The options available for defining end conditions depend on the type of element you selected to define the cross section. For example, if you want to be able to control the tangency of a BlueSurf feature with respect to an adjacent surface, use an edge on the surface as the cross section rather than, for example, the sketch that was used to construct the adjacent surface.

Some end condition options add variables to the variable table, which you can then edit to control the shape of the feature.

What are you looking for?
How do I
Learn more about
Look up more details