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By Root 985 0

3D sketches act more like sketch entities in that if they are under-defined, they can move around inside the sketch. Watching their sketch planes move in a sketch is very unsettling for most users. Figure 20.4 shows the PropertyManager interface for creating 3D planes; however, keep in mind that the plane does not maintain the original relation to these initial references. The parent-and-child relations that SolidWorks users are used to are suspended for this one function, or work in the reverse from what you normally expect.

FIGURE 20.4

The PropertyManager for creating 3D planes

A 3D plane cannot be fully defined unless there is some sketch geometry on the plane that is in turn related to something else. Limited types of sketch relations can be applied directly to the actual plane. Horizontal and vertical relations cannot be applied directly to the plane to orient it. Horizontal and vertical relations of entities on the plane are relative only to the plane and not to the rest of the part; therefore, making a line horizontal on the plane does not mean anything when the plane rotates (which it is free to do until it is somehow constrained to prevent this).

Beyond this, when a plane violates a sketch relation, the error is not reported, which severely limits the amount of confidence that you can place in planes that are created in this way. The biggest danger is in the plane rotating, because that is the direction in which it is most difficult to fully lock down. The best recommendation here is to create reference sketch lines with relations to something stable, preferably outside of the 3D sketch.

If you choose to use 3D planes, you can activate them for sketching by double-clicking a plane. The plane is activated when it displays a grid. You can double-click in an empty space to deactivate the plane and return to regular 3D Sketch mode. The main thing that you give up when abandoning 3D sketch planes is the ability to use the dynamic drag options when all loft or boundary sketches are made in a single 3D sketch.

Limiting path segments

Some path segments that are allowed in 3D sketches can only be used if you sketch them on a plane. These entities include circles and arcs, and can include splines, although splines are not required to be on a plane. To sketch on a 3D plane (a plane created within the 3D sketch), you can simply double-click the plane.

Some sketch entities and tools exist which you cannot create or use inside a 3D sketch, even if a sketch plane is activated. These are

• Autodimension

• Fully Define Sketch

• Modify Sketch

• Sketch Slot

• Ellipse

• Polygon

• Dynamic Mirror

• Sketch Mirror

• Offset Entities

• Split Entities

• Sketch text

• Sketch Picture

To sketch on a standard plane or reference geometry plane, you can Ctrl+click the border of the plane with the sketch entity icon active or double-click the plane. The space handle moves, indicating that newly created sketch entities will lie in the selected plane.

Using dimensions in 3D sketches

Dimensions in 2D sketches can represent the straight-line distance between two points, or they can represent the horizontal or vertical distance, depending on the position of the cursor when you place the dimension. In 3D sketches, dimensions between points are always the straight-line distance. If you want to get a dimension that is horizontal or vertical, you should create the dimension between a plane and a point (the dimension is always measured normal to the plane) or between a line and a point (the dimension is always measured perpendicular to the line). For this reason, reference sketch geometry is often used freely in 3D sketches, in part to support dimensioning.

This is one of the differences between 2D and 3D sketches that users find difficult to manage. If you are used to visualizing dimensions within 2D sketches, direction-controlled dimensions in 3D sketches can be difficult to visualize, and even more difficult to create.

Using the Weldment Tools

Like the Sheet Metal tools, the Weldment tools