SolidWorks 2011 Parts Bible - Matt Lombard [268]
When using the Fill Surface, it is best to have a patch completely bounded by other surfaces, as shown in Figure 20.11. Fill Surface can work with a boundary that is not enclosed, but it works better with a closed boundary.
You can set boundary conditions as Contact, Tangent, or Curvature. Contact simply means that the faces touch at an edge. Tangent means that the slopes of the faces on either side of the edge match at all points along the edge. Curvature means curvature continuous (or C2), where the Fill Surface matches not only tangency, but also the curvature of the face on the other side of the boundary edge. This results in a smoother transition than a transition that is simply tangent.
When you select the Optimize Surface option, SolidWorks tries to fit the four-sided patch into the boundary. Notice that on this part, even though the Optimize surface option is selected, it is clearly being ignored because the boundary is a six-sided gap and cannot be patched smoothly with a four-sided patch. It is not necessarily an improvement to make a Fill Surface optimized, even when it works.
Constraint curves can influence the shape of the Fill Surface. An example of this is shown in Figure 20.13. The construction splines shown on the faces of the part were created by the Intersection Curve tool and enabled the spline used for the constraint curve to be made tangent to the surface.
FIGURE 20.13
The Fill Surface feature with constraint curves
Using MidSurface
The MidSurface feature is not used very often. It was probably originally intended to be used in conjunction with analysis tools to create plate elements for thin-walled structures. It works on parallel faces of a solid, creating a surface midway between the faces. If the faces have opposing draft (such that a wall is wider at the bottom than at the top), then the MidSurface will not work. It works on linear walls and cylindrical walls, but not on elliptical or spline-based shapes. The PropertyManager for the MidSurface is shown in Figure 20.14.
FIGURE 20.14
The MidSurface PropertyManager
Similar to the Planar Surface, you can also use the MidSurface to create a surface that can be used like a plane. No plane type can create a symmetrical plane, but using a MidSurface, you can create a symmetrical Planar Surface between parallel walls.
Using Replace Face
The Replace Face feature does not create new surface geometry, but it does integrate existing surface geometry into the solid. It replaces selected faces of a solid or surface body with a selected surface body. Replace Face is one of the few tools that can add and remove material at the same time with a single feature.
If you were to manually perform the functions that are done by Replace Face, then you would start by deleting several faces of the solid, then extending faces, and then trimming surface bodies, and finish by knitting all the trimmed and extended faces back into a single solid body.
This is a very powerful and useful tool, although it is sometimes difficult to tell which situations it will work in. Figure 20.15 shows a part before and after a Replace Face feature has been added. The surface used to replace the flat face of the solid has been turned transparent. The first selection box is for the original face or faces, and the second selection box is for the surface body with the new faces. The tool tips for each of the boxes are Target Faces For Replacement and Replacement Surface(s), which seem a little ambiguous. I like to think of them as Old (top) and New (bottom).
FIGURE 20.15
Using Replace Face
Using Untrim Surface
The Untrim Surface is discussed in the terminology section of this chapter. You can use it either selectively