Freeform operations allow the design of a wide range of components, characterized by smoothly curved shapes, which are not easily achieved by conventional engineering methods, if at all.
In the same way that Creo Elements/Direct Modeling interpolates points to create a line, Creo Elements/Direct Modeling can interpolate a series of profiles or edges to create faces. In this way, the freeform operations Loft and Loft to Part create material in a freeform-curve manner either between workplanes (1), between parts (2), or between parts and workplanes (3).
Loft allows you to create a freeform part by joining multiple profiles drawn in a set of workplanes. You can also use lofting to remove material from a part. By removing a loft from a part, you sculpt out material from the target part.
Profiles and parts for lofting
You can use either parts, profiles in workplane sets, or a combination of both in a lofting operation. The profiles used for lofts are created in the same way as profiles for any other creation or modification operation. In lofting operations, however, each workplane belongs to a set and has at least one profile. These profiles are joined to the profiles of other workplanes or to the edges of a part.
You can use the smooth option of the loft function to remove edges between two curved faces which have a common tangential transition. The vertices of these edges are also removed. This generates a smooth loft surface with a continuous tangential transition where possible.
Matchlines for lofting
Matchlines show where you want the vertices of 2D profiles or parts or a combination of the two to be joined together during a loft operation. When you begin the loft command, those vertices are joined together along that matchline to create the new loft.
Each part and each profile participating in the loft operation must have one matchline joining it to the next profile or part. All matchlines must point in the same direction. The number of involved vertices must be identical for each profile or part.
Freeform parts imply certain limitations on later 3D modifications: Freeform faces cannot grow as is necessary for some blend and taper operations, and it is not possible to taper a freeform face.
The workplane set for lofting
Create the workplane set before creating the workplanes for the loft operation. You must then specify this workplane set for each workplane which you define. This way, Creo Elements/Direct Modeling groups all workplanes participating in a loft into the same workplane set. When a loft command is started, the entire set becomes active.
The workplanes that you choose for the set do not need to be parallel to each other, and they can be positioned anywhere in 3D space. If you want a closed lofted part, the workplanes are cannot be parallel. This would result in an error message.
Lofting around a common edge
Sometimes it is necessary to create a part from profiles that share a common edge as shown below.
If tangent conditions are applied to any of the workplanes, AutoWeight is automatically switched on and greyed out in order to avoid self-intersections on the surface.
If two workplanes share a common edge, then any additional workplanes must also share this edge. This means that the loft operation shown below will fail.
To prepare for lofting,
1. Create and position the workplanes and/or parts.
2. Create a profile on each involved workplane. Each profile and part face must have at least one vertex. All profiles and part face boundaries must have the same number of vertices.
3. Connect the profiles with profile matchlines.
4. Complete the connection with part matchlines (for Loft to Part).
Additionally, Creo Elements/Direct Modeling provides tools to help you control and change the loft between profiles:
• Tweak a matchline at a profile vertex.
• Rotate the matchlines on a profile.
• Insert an additional workplane (with profile).
• Remove a workplane.
• Add tangency conditions to a workplane, profile, or profile vertex.
• Remove tangent conditions from a workplane, profile, or profile vertex.
You should have all profile matchlines and tangency conditions for profiles or workplanes set before you start adding part faces and part matchlines to the loft definition.
You cannot modify any of the above settings once you entered the Loft to Part option menu.
