SolidWorks 2011 Assemblies Bible - Matt Lombard [171]
Using arc segments
When arc sketch segments are part of the selection for a Structural Member, a Merge arc segment bodies option appears after the selection box in the Selections panel. This means that any tangent arc segment will be joined to the entities to which it is tangent, but any non-tangent entities will create separate bodies.
A tangent arc is shown in the curved leg brace shown in Figure 20.11, along with the Merge arc segment bodies option in the PropertyManager.
FIGURE 20.11
A tangent arc segment used in a Structural Member feature
If the Merge arc segment bodies option is not selected, then a separate body is created for arc segments. The Merge arc segment bodies option applies to the whole feature, and cannot be set selectively for individual arc segments within the selected sketch entities; it is either selected for all or deselected for all. If some arc segment bodies are merged and others are not, then you should create separate Structural Member features.
It is also a curious limitation that only one arc may be selected if the selected path segments are disjointed. For example, you cannot select the two arcs for two J shapes that do not touch in the same Structural Member feature. The obvious work-around is to create two separate groups.
Patterning bodies and sketching with symmetry
Bodies created by the Structural Member feature can be patterned and mirrored. Remember that there is a difference between patterning features and patterning bodies. The Move/Copy Bodies feature is also appropriate for creating bodies to be used in the weldment, although the Structural Member feature does not create them directly.
This is mentioned here to emphasize the point that sketching with symmetry is still important, although it is more difficult with 3D sketches than with conventional 2D sketches. Symmetry in a 3D sketch can only be used when a plane is activated, and you can activate regular reference geometry planes, not just 3D sketch planes. This is also mentioned because in larger weldments (or when using slower computers), performance may be an issue, and mirroring or patterning bodies is certainly a performance enhancement over building parametric features.
Creating configurations
When you start creating a weldment, SolidWorks automatically creates a derived configuration. Both configurations are named Default, but they have different descriptions. The parent configuration description is As Machined, and the derived, or indented, configuration description is As Welded.
This arrangement holds true for any additional top-level configurations that you create in the part; they will all get the description As Machined and inherit an identically named derived configuration with the description As Welded. These configurations are meant to help you create drawings where the raw weldment is distinguished from the weldment after it has been machined, ground, and drilled.
Using the Trim/Extend feature
In situations where you must create multiple Structural Member features, thus creating intersecting bodies, you must deal with the interferences using the Trim/Extend feature. An example of this is shown in Figure 20.12. The legs and braces shown are all being trimmed by a single face on the bottom side of the rectangular section of the frame, where the small arrow appears.
FIGURE 20.12
Using the Trim/Extend feature
Bodies may be trimmed by planar faces or other bodies. Bodies may also be trimmed before they are mirrored or patterned. Although trimming with faces is faster, it may not give the same geometrical results.
The Extend option enables either trimming or extending, as appropriate. If the Extend option is