SolidWorks 2011 Parts Bible - Matt Lombard [109]
Because surfaces are the underlying building blocks from which solids are made, it would make sense to teach surfaces first, and then solids. However, the majority of SolidWorks users never use surfacing, and do not see a need for it; therefore, surface functions are generally given a lower priority.
Cross-Reference
Refer to Chapter 20 for surfacing information. For a comprehensive look at surfacing and complex shapes, see the SolidWorks Surfacing and Complex Shape Modeling Bible (Wiley, 2008).
Exploring loft end constraints
Loft end conditions control the tangency direction and weighting at the ends of the loft. Some of the end constraints depend upon the loft starting or ending from other geometry. The optional constraints are covered in the following sections.
None
The direction of the loft is not set by the None end constraint, but the curvature of the lofted faces at the ends is zero. This is the default end constraint for two-section lofts. This means that at the ends of the loft using the None end constraint, the loft has no curvature, and is tangent to some direction controlled by the location of the previous profile.
Default
The Default end constraint is not available for two-section lofts, only for lofts with three or more sections. This end constraint applies curvature to the end of the loft so that it approximates a parabola being formed through the first and last loft profiles.
Tangent to Face
The Tangent to Face end constraint is self-explanatory. The Tangency to Face option includes a setting for tangent length. This is not a literal length dimension, but a relative weighting, on a scale from 0.1 to 10. The small arrow to the left of the setting identifies the direction of the tangency. Usually, the default setting is correct, but there are times when SolidWorks misidentifies the intended tangency direction, and you may need to correct it manually.
The Next Face option is available only when lofting from an end face where the tangency could go in one of two perpendicular directions. This is shown in Figure 7.15.
Apply to All refers to applying the Tangent Length value to all the tangency-weighting arrows for the selected profile. When you select Apply to All, only one arrow displays. When you deselect it, one arrow should display for each vertex in the profile, and you can adjust each arrow individually.
Curvature to Face
The difference between tangency and curvature is that tangency is only concerned with the direction of curvature immediately at the edge between the two surfaces. Curvature must be tangent and match the radius of curvature on either side of the edge between surfaces. This is often given many names, including curvature continuity and c2 or g2. Lofted surfaces do not usually have a constant radius; because they are like splines, they are constantly changing in local radius.
Direction Vector
The Direction Vector end constraint forces the loft to be tangent to a direction that you define by selecting an axis, edge, or sketch entity. The angle setting makes the loft deviate from the direction vector, as shown in Figure 7.15. The curved arrows to the left identify the direction in which the angle deviation is going.
FIGURE 7.15
Examples of end constraints
Displaying isoparameter U-V lines
The mesh or grid shown in the previous images appears automatically for certain types of features, including lofts. The grid represents isoparameter lines, also known as NURBS mesh or U-V lines. This mesh shows the underlying structure of the faces being created by the feature. If the mesh is highly distorted and appears to overlap in places, then it is likely that the feature will fail.
You can show or hide the mesh through the right mouse button (RMB) menu when editing or creating a Loft feature, unless the SelectionManager is active. In this case, you can see only SelectionManager commands in the RMB menu. In