SolidWorks 2011 Assemblies Bible - Matt Lombard [91]
The problem with a broken reference is that it has absolutely no advantage over a locked reference. For example, while locked references can at least be unlocked, broken references cannot be repaired. The only thing that you can do with a broken reference is to use Display/Delete Relations or to edit features manually to completely remove the external reference.
Best Practice
Best practice is to avoid placing yourself in a situation where you are using broken references. Parametric relations should not change if the driving geometry does not change.
You cannot selectively lock or break external relations. For example, all the external relations in the part can be locked or broken, or none of them can be locked or broken. If you need to disable relations selectively, then you should consider suppressing features, sketch relations, end conditions, or sketch planes.
List External References
You can access the locked and broken references through the List External References option on the RMB menu of any feature with an external reference symbol. Figure 10.15 shows the name and path of the assembly where the external reference was created, as well as the part names and entity types.
FIGURE 10.15
The External References dialog box
No External References
To access the No External References button on the Assembly toolbar, choose Tools⇒Options⇒External References⇒Do Not Create References External To The Model from the menus. As its name suggests, this setting prevents external relations from being created between parts in an assembly. When you offset in-context edges or use Convert Entities, the resulting sketch entities are created without relations of any type.
This lack of references includes the InPlace mate, which is not created when a part is created in-context. As a result, when you add the part to the assembly, if you exit and later re-enter Edit Part mode, SolidWorks reminds you that the part is not fixed in space by displaying the warning shown in Figure 10.16.
This message should remind you that in-context features should be used only on parts that are fully positioned in the assembly.
FIGURE 10.16
The dialog box that warns you about adding in-context relations to an underdefined part
External reference settings in Tools⇒Options
The Tools⇒Options⇒External References pane of settings controls many aspects of the behavior of external references. One of these references was discussed earlier, No External References, and the other reference, Multiple Contexts, is discussed in the next section. This pane in the Tools⇒Options dialog box is shown in Figure 10.17.
FIGURE 10.17
The Tools⇒Options⇒External References pane
Looking at in-context best practices
This technique requires a fair amount of discipline, restraint, foresight, and judgment. The potential problems associated with overuse or misuse of in-context techniques primarily include performance problems (speed) and lost references due to file management issues. Users may also experience problems with features or sketches that change with each rebuild. The following section contains best practice suggestions that can help you avoid these situations.
Working with multiple contexts
Multiple contexts occur when a part has references that are created in multiple assemblies. By default, multiple contexts are prevented from happening. If you place a part that already has external references into a different assembly, a warning appears, as shown in Figure 10.18.
FIGURE 10.18
The warning message that appears about multiple contexts
Although SolidWorks displays many warnings about multiple contexts, you may still run into situations where you need to use them. For example, you may have a subassembly where a part, such as a top plate of a stand, has in-context references to locate a