SolidWorks 2011 Parts Bible - Matt Lombard [138]
FIGURE 9.8
A geometry pattern test
The pattern of the rectangular bosses cannot use Geometry Pattern because the face that is merged is not merged in all pattern instances. The pattern of truncated cylinders shown on the same part as the pattern of rectangular bosses can use Geometry Pattern because the flat face is merged in every pattern instance. The circular pattern in the image to the right in Figure 9.9 also allows Geometry Pattern for the same reason.
FIGURE 9.9
Merged faces
In some situations, SolidWorks error messages may send you in a loop. One message may tell you that the pattern cannot be created with the Geometry Pattern turned on, so you should try to turn it off. When you do that, you may get another message that says the pattern will not work, and that you should try to use the Geometry Pattern setting. In cases like this, you may try to use a different end condition for the feature that you want to pattern, or change the selection of features patterned along with the feature, such as fillets. You may also try to pattern bodies or even faces rather than features. These last two options are covered in the following sections.
Patterning Bodies
I cover multi-bodies in depth in Chapter 20, but I will briefly discuss the topic here. Any discussion of patterning is not complete without a discussion of bodies because using bodies is an available and highly useful option with all the pattern and mirror types.
SolidWorks parts can contain multiple solid or surface bodies. A solid body is a solid that comprises a single contiguous volume. A surface body is different — think of it as a sheet knitted together from several faces — but it can also be patterned and mirrored as a body.
There are both advantages and disadvantages to mirroring and patterning bodies instead of features. The advantages can include the simplicity of selecting a single body for mirroring or patterning. In cases where the geometry to be patterned is complex or there is a large number of features, patterning bodies also can be much faster. However, in the example used earlier with patterning features in a 20-by-20 grid of holes, when done by patterning a single body of 1" × 1" × .5" with a .5" diameter hole, patterning bodies gives a rebuild time of about 60 seconds with or without Verification on Rebuild. The function combines the resulting bodies into a single body that takes most of the time. This says that for large patterns of simple features, patterning bodies is not an efficient technique. Although I do not have an experiment in this chapter to prove it, it seems intuitive that creating a pattern of a smaller number of complex bodies using a large number of features in the patterned body would show a performance improvement over patterning the features.
Another disadvantage of patterning or mirroring bodies is that it does not allow you to be selective. You cannot mirror the body minus a couple of features without doing some shuffling of feature order in the FeatureManager. Another disadvantage is that if the base of the part has already been mirrored by a symmetrical sketch technique, then body mirroring is not going to help you mirror the subsequent features. In addition, the Merge Bodies option within the mirror feature does not work in the same way that it works for other features. It merges only those bodies that are part of the mirror to bodies that are part of the mirror. Pattern Bodies does not even have an option to merge bodies. Both of these functions are often going to require an additional combine feature (for solid bodies) or knit (for surface bodies) to put the final results together.
Some of these details may seem obscure when you're reading about them, but when you begin to work patterning bodies and begin trying to merge them into a single body, read over this section again. The inconsistency between the Merge option existing in Mirror but not in Pattern, as well as the functional discrepancy between the Merge in Mirror and the Merge Result in, say, Extrude is unexplainable,