SolidWorks 2011 Parts Bible - Matt Lombard [18]
FIGURE 1.25
The fully defined sketch cannot be dragged, and there are no degrees of freedom.
Parametric relations within a sketch control how the sketch reacts to changes from dimensions or relations within the sketch or by some other factor from outside the sketch. Other factors can also drive the sketch, such as equations, other model geometry that is external to the sketch, and even geometry from another part in an assembly, as you shall see later.
Understanding Design Intent
Design Intent is a phrase that you will hear often among SolidWorks users. I like to think of it as “design for change.” Design Intent means that when you put the parametric sketch relations together with the feature intelligence, you can build models that react to change in predictable ways. This gives you a great deal of control over changes.
An example of Design Intent could be a statement that describes general aspects that help define the design of a part, such as “This part is symmetrical, with holes that line up with Part A and thick enough to be flush with Part B.” From this description, and the surrounding parts, it is possible to re-create the part in such a way that if Part A or Part B changes, the part being described updates to match.
Some types of changes can cause features to fail or sketch relations to conflict. In most situations, SolidWorks has ample tools for troubleshooting and editing that you can use to repair or change the model. In these situations, it is often the Design Intent itself that is changing.
Best Practice
When editing or repairing relations, it is considered best practice to edit rather than delete. Deleting often causes additional problems farther down the tree. Many users find it tempting to delete anything that has an error on it.
Editing Design Intent
One of the most prominent aspects of design in general is change. I have often heard it said that you may design something once, but you will change it a dozen times. This concept carries over into solid modeling work. Design Intent is sometimes thought of as a static concept that controls changing geometry. However, this is not always the way things are. Design Intent itself often changes, thus requiring the way in which the model reacts to geometric changes to also change. Fortunately, SolidWorks has many tools to help you deal with situations like this.
Choosing sketch relations
Seeing the sketch relation symbols is the best tool for visualizing Design Intent. You can show or hide icons that represent the relations by choosing View⇒Sketch Relations. When shown, these relations appear as an icon in a small colored box in the graphics area next to the sketch entity. Clicking the icon highlights the sketch elements involved in that relation. Refer to Figures 1.19 through 1.25 for examples of these relations.
Tip
The View Sketch Relations option is an excellent candidate for use with a hotkey, thus enabling you to easily toggle it on and off.
Cross-Reference
For more information on creating and managing hotkeys, see Chapter 2.
You can use the sketch relation icons on the screen to delete relations by selecting the icon in the graphics area and pressing Delete on the keyboard. You can also use them to quickly determine the status of sketch relations by referring to the colors defined earlier.
Selecting display/delete relations
The Display/Delete Relations tool enables you to list, sort, delete, and repair sketch relations. You can find the Display/Delete Relations tool on the Sketch toolbar. The sketch status colors defined earlier also apply here, with the relations appearing in the appropriate color. (Relations are not shown in blue or black, only the colors that show errors, such as red, yellow, and brown.) This tool also enables you to group relations by several categories:
• All in This Sketch
• Dangling
• Overdefining/Not Solved
• External
• Defined in Context