Understanding History-Based Modeling
In addition to being feature-based, SolidWorks is also history-based. To show the process history, there is a panel to the left side of the SolidWorks window called the FeatureManager. The FeatureManager keeps a list of the features in the order in which you have added them. It also enables you to reorder items in the tree (in effect, to change history). Because of this, the order in which you perform operations is important. For example, consider Figure 1.16. This model was created by the following process, left to right starting with the top row:
Create a sketch.
Extrude the sketch.
Create a second sketch.
Extrude the second sketch.
Create a third sketch.
Extrude Cut the third sketch.
Shell the model.
If the order of operations used in the previous part were slightly reordered (by putting the shell and fillet features before Step 6), the resulting part would also look slightly different, as shown in Figure 1.17.
Figure 1.18 shows a comparison of the FeatureManager design trees for the two different feature orders. You can reorder features by dragging them up or down the tree. Relationships between fea- tures can prevent reordering; for example, the fillets are dependent on the second extruded feature, and cannot be reordered before it. This is referred to as a Parent/Child relationship.
Reordering and Parent/Child relationships are discussed in more detail in Chapter 11, Editing and Evaluation.
ON the CD-ROM
The part used for this example is available in the material from the CD-ROM, named Chapter 1 — Features.SLDPRT. Parts on the CD-ROM exist for both 2007 and 2009
The order of operations, or history, is important to the final state of the part. For example, if you change the order so that the shell comes before the extruded cut, the geometry of the model changes, removing the sleeve inside instead of the hole on top. You can try this for yourself by opening the part indicated previously, dragging the Shell1 feature in the FeatureManager, and dropping it just above the Cut-Extrude1 feature.
You can only drag one item at a time in the FeatureManager. So you may drag the Shell, and then drag each of two fillets, or you could just drag the Cut feature down the tree. Alternatively, you can put the shell and fillets in a folder and drag the folder to a new location. NOTE
Reordering is limited by parent-child relationships between dependent features.