Datums are used to establish a plane of reference. They can be defined by a datum plane or a planar part face. When a sketch is created, you are prompted to select an insertion plane. When you select a datum plane or planar face, the sketch is aligned with the plane and sketch geometry is created on the plane.

 

The sketch is parametrically constrained to the plane on which it is created. If the plane moves, the sketch will move with it during the next history replay. There are three default datum planes as shown below.

 

 

Datum planes are also used to create certain features that do not require the use of a sketch such as parting lines and section curves. The Insert Datum Plane command creates datum planes using a variety of methods.

 

 

 

In VX, a sketch can be a two-dimensional stand alone root object like a part or drawing packet. Root sketches can be inserted into any number of parts to drive feature geometry.

 

While in a part, a sketch is a two-dimensional geometry group created on a datum plane or planar part face, whose primary function is to drive a part feature. Sketches can be created on-the-fly while a command to create a feature is executed.

 

The feature command is temporarily halted while the sketch is created and then resumes using the newly created sketch. The sketch remains associated with the feature.

 

A sketch can also be created for use during later commands. VX is flexible by allowing the use of various types of sketches. A sketch can be an open or closed profile. It can be undimensioned, partially dimensioned, underconstrained, or fully constrained.

 

For solid features, the sketch geometry should not intersect itself. For surface features, the sketch geometry may intersect itself, but multiple shapes may result depending on the geometry used. The figures below show examples of sketch type that can exist in a VX part.

 

 

 

 

While it is possible to overconstrain a sketch in VX, mechanisms are in place to guard against it. For example, if you add a dimension that would result in the sketch being overconstrained, it is automatically converted to a reference dimension.

 

VX makes dimensioning and constraining easy by analyzing the sketch and performing both functions automatically during most sketch commands that create geometry.

 

There is also a command that automatically dimensions and constrains all free geometry. You may also interactively analyze the constraint system and the associations with geometry. You can go back and add geometry, dimensions, or constraints to a sketch any time. The figure below shows a few sketch examples.

 

Notes

Selecting Points from Sketches (see CAD Tips & Techniques).

 

 

 

External reference geometry is 3D part geometry referenced by a sketch. Part points, edges, or face silhouettes can be projected onto the sketch plane. Reference points and curves can also be created where part curves and faces intersect the sketch plane. This external reference geometry can be used to create or constrain sketch geometry.

 

External reference geometry can also be converted to normal sketch geometry. Referencing external geometry will allow the sketch to adapt to changes in the part design. If part geometry that is externally referenced changes, the sketch will regenerate accordingly during the next history regen. The figure below illustrates how part geometry is externally referenced into a sketch.

 

 

Solid feature commands (e.g., extrude, revolve, sweep, loft, fillets, chamfers, ribs, etc.) can be performed on open or closed shapes. While a solid has been traditionally defined as a closed shape, it is important to remember that VX generally allows you to create these features even if the shape is open (i.e., one or more faces of the solid are missing). Only the faces that interact with the feature are modified.

 

 

There is a special type of solid feature called a base feature. Base features are used to begin the construction of a new part by specifying its basic shape. Other features are then applied to the basic shape until the part is complete. A part can be more than one base feature. Many solid features use one or more sketches as input (e.g., bosses and cuts) while others do not require a sketch (e.g., fillets and chamfers).

 

 
 

 

Surface features (called faces) can be created or modified separately in traditional surface modeling fashion or they can be used individually or in shapes to trim, divide, or replace portions of a solid (i.e., open or closed shape). Advanced linear, circular, or conic faces can be created that blend between other face edges, wireframe geometry, or sketches. Once created, faces can be trimmed, split, extended, exploded, sewn, reversed, merged or modified by their control points.

 

 

Faces can be visually altered for inspection or display purposes such as setting their number of isolines or display tolerance. They can also be analyzed in a variety of ways for curvature and continuity. Face edges that meet to form shapes can be matched or made continuous. As a hybrid modeler, VX treats solid features and surface features in much the same way. Surface feature operations can be applied to solids and vice versa. Ultimately, a solid is nothing more than a closed shape.

 

 

 

 

 

Wireframe features such as points, lines, circles, arcs, and curves can be created and modified in traditional wireframe modeling fashion or they can be used in a variety of commands to create faces. Faces can be extruded, revolved, swept, lofted, or meshed, based on wireframe features. A cloud of wireframe point features can be used to create a face that passes through each point.

 

Wireframe features can also be used to create advanced linear, circular, or conic faces that blend between two boundaries. Wireframe curves can be created directly by specifying control points or indirectly by intersecting two faces or by projecting curves or edges onto a face. Curves can be blended, offset, extended/trimmed, or modified by moving their control points. Wireframe features can be used to create faces that in turn create solids. They can also be extracted from the edges of a solid or face at any time.