SolidWorks 2010 Bible

Chapter 31: Using Weldments ....................................................................................................

FIGURE 31.2

The Four Viewport view

Sketch relations in 3D sketches

Sketch relations in 3D sketches are not exactly the same as in 2D sketches. Improvements have

been made in the past several versions, but 3D sketches still lack some important bits of function-

ality. Pierce is not applicable in a 3D sketch, and is replaced by Coincident, because in 3D

sketches, there is no difference between Pierce and Coincident. Relations are not projected into a

plane in a 3D sketch the way they are in 2D.

On the other hand, several other relations are available in 3D sketches that are not found in 2D

sketches, such as AlongX, AlongY, AlongZ, and OnSurface.

As mentioned earlier, relations in 3D sketches are not projected like they are in 2D sketches. For

example, an entity in a 2D sketch can be made coincident to an entity that is out of plane. This is

because to make the relation, the out-of-plane entity is projected into the sketch plane, and the rela-

tion is made to the projection. In a 3D sketch, Coincident means Coincident, with no projection.

As a general caution, keep in mind that solving sketches in 3D is more difficult than it is in 2D.

You will see more situations where sketch relations fail, or flip in the wrong direction. Angle

dimensions in particular are notorious in 3D sketches for flipping direction if they change and go

across the 180-degree mark. When possible, it is advisable to work with fully defined sketches,

and also to be careful (and conservative) with sketch relations.