CAD wireframe models do not contain the surface information that a CAD solid model has; therefore, a CAD wireframe model cannot be imported and meshed with the direct transfer technology.
Instead, the wireframe model consists of pure lines, circles, arcs, and so on. These objects are ideal for creating beam and truss models. The wireframe models can also be imported as constructions objects and used as the edges of a hand-built mesh, such as meshes between two objects. If the geometry is planar and encloses one or more regions, it can be automatically meshed with the 2D mesh generator. (See Meshing Overview:.)
AutoCAD DXF/DWG files can be imported using the Open command and selecting either AutoCAD DXF (*.dxf) or AutoCAD DWG (*.dwg) in the Files of type: drop-down box. There are several options that can be used to import DXF/DWG files. These options are selected by pressing the Options button on the Open dialog.
When opening a drawing, the software detects if the drawing contains only wireframe entities or only surface/solids and uses the appropriate import settings. The import setting If both exists, import As: determines what entities import if both are present in the drawing.
Seefor the surface/solid import options. The options for importing wireframe drawings are as follows:
If the model will be analyzed using 2D elements, it must be imported into the YZ plane. Activate the Transform to YZ Plane (for 2-D elements) check box.
If the DXF represents a 3D model, the entities can be imported directly into the display area by deactivating the Drawing is 2-D drawn in check box.
All objects can be imported as either construction objects or as regular mesh lines.
AutoCAD properties are translated as follows. The part number applies to construction objects and regular mesh lines.
If the ID of an entity in the DXF file cannot be used in Autodesk Simulation, the entity will be placed with the number specified in the Replace Invalid _ IDs with: field. One common example of this is Layer 0 in AutoCAD. Entities cannot be placed in Part 0 in Autodesk Simulation.
If some entities are not connected properly in the sketch or 3D model, you can loosen the tolerance value. This can be done by activating the Use Tolerance check box and specifying a value in the adjacent field. All values beyond the decimal point specified will be truncated. For example, using the default tolerance of 1E-4, all digits at five decimal points or more will be truncated. The tolerance should only be used if initial import does not succeed.
DXF Entities Supported:
*Files with entities not listed will still be imported. The non-supported entities will be ignored.
If your DXF/DWG file contains blocks, you have the option to Import Blocks As Separate Parts.
Wireframe IGES files can be imported using the Open command and selecting the Wireframe IGES (*.igs, *.iges) option in the Files of type: drop-down box. There are different methods that can be used to wireframe files. These methods can be set by pressing the Options button on the Open dialog.
If all the entities in each part lie in a single plane, the entities in the part can be imported into a sketch by selecting the Import as 2D objects check box. (Each part is treated separately.) If the model will be analyzed using 2D elements, it must be imported into the YZ plane. Activating the Import into YZ plane check box will translate the positive X axis in the IGES file to the positive Y axis in the sketch and the positive Y axis in the IGES file to the positive Z axis in the sketch.
If the wireframe file is in a plane other than the XY or YZ plane and you need to create 2D elements, it can still be transformed to the YZ plane as follows:
If the Import as 2D objects check box is not activated, then the file will be imported as 3D construction objects. If the Import as 2D objects check box is activated and the entities within the part do not lie in the same plane, the entities within that part will be imported as 3D construction objects.
If the part number of an entity in the IGES file cannot be used, the entity will be placed with the number specified in the Replace Invalid Part IDs with: field.
IGES Entities Supported:
Circles and Arcs
Copious data read in as individual lines
Parametric Spline Curve
Rational B-Spline Curve