SolidWorks 2011 Assemblies Bible - Matt Lombard [93]
In some situations, configurations work well with in-context relations. One example of this would be when an assembly has many configurations used for positioning parts. In this case, you would use one configuration for the sole purpose of creating in-context relations.
Using in-context with motion
You should make in-context references between parts where there is no relative motion. The parts themselves can move relative to the rest of the assembly, but they should remain stationary relative to one another. The parts should also be fully defined to ensure that they would not move; you should not simply assume that you would avoid dragging underdefined parts. This is because if one part drives a feature on another part, and the parts move relative to one another, the in-context feature is also likely to move within its parent part.
In some cases, such as an assembly of imported parts, it may make sense to fix parts in bulk rather than to mate them. When you are using in-context relations, you need to take extra care to ensure that the parts do not move around. When parts move around, in-context features also move.
FIGURE 10.21
Combining in-context references with configurations
Obviously, if the motion is around a circular hole and the in-context feature is circular and is not affected by the rotation of the referenced part, then it makes less difference; however, if there is a keyway, that may change things. You need to pay attention when combining underdefined parts and in-context features.
Best Practice
For best practice, you should avoid in-context relations between parts when relative motion is allowed between these parts.
Working with in-context with multiple instances
Another situation that can cause problems is when multiple instances of an in-context part are being used in the assembly. In cases like this, you need to be careful and consistent, by always using the same instance to create the in-context relations. You can do this by putting parts into folders, or by giving the in-context part a special component color.
One trick is to use one instance of an in-context part for the in-context relation, and a second instance of the part to allow motion. In-context relations are tied to one specific instance of a part, regardless of how many of those parts are in the assembly. You might want to set the driving in-context part aside by putting it in a folder, changing its color, or hiding it.
Using in-context and file management
Understanding what you are doing with file management is imperative when working with parts that depend on in-context features. Because the references are stored in both the part that is doing the referencing and the assembly where the reference is created, improperly changing the name of either document or even the referenced document is bound to cause problems. For example, if you rename an in-context part using Windows Explorer, then the assembly will not recognize the part. This also means that any in-context references will not update. The part will show the out-of-context symbol.
Best Practice
For best practice, you should use either the SolidWorks Save As command or SolidWorks Explorer to rename parts and assemblies. This applies to all parts and assemblies, but even more to in-context documents.
Using in-context and mates
A section on in-context best practices would not be complete without issuing the warning against mating to in-context features. Mating parts to in-context features creates a parametric daisy chain, thus establishing an order in which assembly features and mates must be solved. This always creates performance problems in assemblies, especially large ones. The SolidWorks AssemblyXpert looks for this condition when examining assemblies.
Working with circular references