CAD terminology and concepts

To understand the CAE data model and part relationships, you must first understand general assembly and CAD data model terminology and concepts.

CAD terminology

• A component object is a non-geometric pointer to the file that contains the component geometry. After you define a component, the part file in which you define it has a new component object. The component object allows the component to be displayed in the assembly without duplicating any geometry.

• A component part is any part used at least once in an assembly. A component may be a sub-assembly consisting of other, lower-level components. Each component object in an assembly contains only a link to its master geometry. When you modify the geometry of one component, all other components in the session using the same master will automatically update to reflect the change.

• A piece part is the lowest level part in an assembly. It contains model geometry and feature information that represents the part, but no component objects. When several parts are brought together into an assembly, the parts and their objects are not copied into the assembly part. Rather, the parts are loaded into memory, and occurrences of those parts are put into the assembly part. For each object in the piece part, an occurrence of that object is made in the assembly part.

• An occurrence of a component is a pointer to geometry in the component file. You can use component occurrences to create one or more references to a component without creating additional geometry. Because geometry is not copied with an occurrence, when you change the component, all occurrences of that component are updated.

• An instance is the term used to indicate the placement of a component part within an assembly part. For each component instance, an occurrence is displayed in the assembly part.

• An assembly is a part file which contains component objects (either piece parts or subassemblies). Assemblies can be multi-leveled. For example, an automobile can consist of the body and two instances of an axle assembly part, which itself consists of an axle and two instances of a wheel assembly part, which itself consists of other parts. Each instance can have more than one associated part occurrence.

• A subassembly is an assembly used as a component in a higher level assembly.

• The displayed part is the part that is being viewed in the graphics window. It can be a piece part or an assembly.

• The work part is the part whose geometry or assembly structure is being modified. The work part can be the same as the displayed part. When the displayed part is an assembly, the work part can be any of the component parts in the assembly. When the displayed part and the work part are different, making modifications to the work part is called Designing in Context.

• A reference set is a named collection or set of geometry from a part. The reference set may be used to simplify the representation or display of the component part in larger or complex assemblies.

Data model terminology

• A tag identifies an object in the data model. The objects are not limited to geometrical objects, but can include parts, instances, and occurrences.

• A prototype is a master copy of a part or object occurrence. To edit an object, you must make the prototype part the work part and modify the prototype object.

Learn more

NX Open for CAE terminology and concepts

CAE terminology and concepts

The importance of the work part in CAE applications

Overview of the CAE data model

Working with objects in the CAE data model

Overview of the CAE solver languages

Working with the CAE solver languages: name strings

Working with the CAE solver languages: property tables

Creating undo marks and forcing model updates

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CAD terminology and concepts, Simcenter 3D 2021.1 Series

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